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#1
Looking around UG I couldnt find a thread dedicated to all things science- So I decided to make one!

This thread is for anybody who has an interest in science or for anybody who has a question.

I dont want to see:

Flaming:

I dont care how ignorant someone is, I dont care how lacking someones scientific knowledge is, I will not tolerate flaming in this thread. This thread is here to help broaden everyones scientific knowledge.

Do not flame anyones scientific beliefs. Each to their own. Do not bring religion into any discussion (see below).

Religion:

Science and religion will never agree so dont post any religious/spiritual/other belief system here- Use the religion thread.

Politics:

Any politics goes in the political thread. If you want to discuss ethics of science then steer clear of politics or religion. This is hard when it concerns moral dilemas, but again religion or politics thread if it is of that nature.

I want to see:

Healthy discussion of science! If you want to write an article, please do not plagerise it, if you do use sources- include links. Use your own words and be detailed in explanations (to the best of your knowledge) and make it understandable so that everyone can access the infomation you are putting across.

I want to see questions, debates and I want people to have fun!

Science sites:

http://www.freewebs.com/science_questions/foreword.htm
http://www.tenthdimension.com/flash.php
www.popsci.com
http://www.newscientist.com/home.ns

------------------------

Credentials:

I have studied A level Chemistry Biology and Physics. Chemistry is my strongest subject followed by biology. Im not too good on physics since I had a very boring, very monotonous teacher. Right now I am at The University of Surrey studying Chemistry. [Maybe I shouldnt post that... People migt come looking for me... To kill me].

Anyway, I want a "dedicated" to use the term loosely, team of people who will help me with the thread. You need GCSE Science or above, have posted atleast three decent scientifically accurate understandable articles and must answer peoples questions as accurately as possible. I will PM you if I think you are worthy.

The Team:

Chemistry

Guitardude19 (First Year University Student)

Biology

Guitardude19 (To A level standard)

Physics
Sat in a lab, curing diseases. They actually LET me play with chemicals!
Last edited by Guitardude19 at Mar 13, 2007,
#2
Articles

Evolution by natural selection- Guitardude19

Evolution through natural selection.

This is the be all and end all so no arguing that evolution is a load of rubbish because if you have half a brain, you will at least understand this long post on this subject. Do not bring religion into it and do not dismiss it. This theory is very real and very true, do not bring any other theories into it because this is the very core of the theory. If you want to bring religion into it then you know what you have to do, get off the thread because religious discussion is not allowed.

EVOLUTION IS NOT A RELIGION IT IS A SCIENTIFIC THEORY!

Evolution is a process by which new species are formed from pre existing ones over a period of time. In order for evolution to occur, all organisms must produce large numbers of offspring, which if they survived would lead to a geometric increase in the size of the population. Despite the fact that organisms have a tendency to increase in numbers due to over production, the population actually remains constant. This is due to the fact that members of the species are constantly competing to survive. This struggle for existence means only a few will survive to breed. Any form of competition be it food territory or availability of mates will only be open to those who are best adapted to the prevailing conditions to survive. Those that are not adapted to suite the environment, or cannot compete adequately with the rest of the population die off. This means that those that go on to breed pass on their genes to the next generation thus the new offspring are better able to survive. However, in any sexually produced offspring of any species, there is always individual variation amongst members of that species. This means that generally, no two offspring are alike. (This excludes twins who are genotypically the same but maybe phenotypically different due to environmental factors). Amongst the offspring of any species within any population, there are some that are able to withstand the prevailing conditions of the environment. This means that some are better able to survive the struggle for existence, and those that are more likely to survive are the ones that are more likely to breed, and therefore produce offspring that are similar to themselves. Advantageous characteristics are therefore passed onto the next generation which allows the next generation to be better adapted to their environment. Over time, the favourable characteristics pass through the population therefore spread through the gene pool. Development of variation over generations leads to the evolution of a new species.

As we have seen, evolution is based on natural selection and those that are better able to survive prevailing conditions, go on to breed. However, in order to breed, these organisms need to be able to survive selection pressures. Selection pressures determine the spread of an allele amongst the gene pool. Where variation forms a normal distribution curve, there will be organisms that have ?average alleles? that allow it to survive prevailing conditions, and there will be organisms that have the extremes of these alleles that make them less able to survive the prevailing conditions. For example, in a population of polar bears, there is a mean fur length, short fur and long fur. If the selection pressure is temperature, the mean hair length and long hair length is favourable in cold temperatures, there for short fur is selected against, therefore short hair polar bears die out, therefore, the short hair allele is no longer in the population (not all short fur bears die because body fat composition may make up for what the fur lacks). This means the mean shifts to allow favourable medium and long fur alleles to prevail in the population and therefore, over time, longer haired species of polar bear develop. Where extreme characters (long fur in this case) are selected for, the mean allele frequency shifts in the population. This is due to a change in the environmental conditions. The colder it gets, the more the long hair allele is favoured (as shorter hair bears die off they cannot pass genes to next generation) therefore more bears are produced with longer fur. This is directional selection where one of the extremes is favoured as conditions change.

Another form of selection is stabilising selection, where the environment selects against the extremes of the population therefore favours the mean. This reduces the allelic variation amongst the population therefore reduces evolutionary change.

There are rare cases where the mean allele in a population is selected against. This is disruptive selection and favours the extremes within the population, therefore two distinct phenotypes are favoured (phenotype determined by genotype) therefore encourages evolutionary change.

Although selection pressures can lead to variation amongst a population and over time, new species can develop, another more common method of evolution that is often over looked is speciation. Speciation is where a new species is formed from groups via isolation mechanisms. Within a population there are demes. A deme is a group of individuals within a species. A deme can breed with individuals from its own deme or other demes, thus keeping the gene pool wide and varied. However, if a deme is prevented from breeding with another deme, the gene pool becomes smaller, therefore separated and therefore isolated. When demes become isolated from other demes, speciation occurs via two mechanisms, allopatric and sympatric speciation.

Allopatric speciation is where a deme becomes geographically isolated by any physical barrier. These can include mountain ranges, rivers, oceans and any other form of physical barriers that prevent two demes from interbreeding.

Sympatric speciation is more complex and involves factors other than geographical factors. This is where reproductive isolation occurs by a number of factors. There may be mechanical isolation where the genitals are not compatible, therefore it is physically impossible for the male anatomy to enter the female anatomy. Even if intercourse can occur, the male gametes maybe prevented from meeting the female gametes as the male gametes may not survive female reproductive tract. Another factor maybe that the gametes do not fuse because they are not compatible. If gametes do fuse, hybrid initability may occur where chromosomal abnormalities may occur preventing the survival of the embryo. Polyploidy may cause hybrid sterilisation. (Polyploidy will be explained later). Also, another factor is behavioural isolation, where courtship rituals prevent reproduction as the rituals differ. A factor with plants is seasonal differences, where some plants release pollen before female parts of plant are developed, but develop in another season.

Another big factor in evolution is variation due to genetic mutations. This can be recombination during prophase one of meiosis. This is where chromatids are exchanged that lead to changes in the genotype. During metaphase one of meiosis there is random distribution of chromosomes, and during prophase one, there is crossing over of homologous chromosomes. These are not necessarily forms of mutations, but that are inbuilt methods of variation where genes are swapped between chromosomes to deliberately change the genotype. A mutation is a change in the structure or the amount of DNA. Any mutation that occurs in somatic cells are not passed on to the next generation. Only mutations that occur in gametes are passed on as these are the cells used in reproduction. A point mutation occurs at a specific locus on a chromosome. These are a change in a specific nucleotide base pair. There can be duplication where a portion of DNA is repeated. There can be insertion, where an extra nucleotide sequence is added in. There can be deletion, where a portion of DNA is removed. Inversion can occur where a portion of the DNA sequence is removed, but joins back on to the chromosome in its reversed position. Substitution can occur where a nucleotide is replaced by another. All of these lead to evolutionary change because they alter the phenotype. Any change in the genotype alters the phenotype so much so a new species is formed as any two organisms now differ.

Another type of mutation that leads to evolutionary speciation is a change in the structure of the chromosomes. During meiosis (pronounced my oh sis) chromosomes form chiamesta. This is where chromosomes break off into chromatids and rejoin. This can lead to new genotypes by similar mechanisms to point mutations. Deletion can occur. This is where a portion of the chromosome is lost, however, this involves a loss of genes and is often fatal. Inversion can occur where the chromatid breaks off and rejoins in its reversed position. The gene sequence is reversed, but the genotype stays the same. This could however, alter the phenotype. This indicates that the sequence of the genes is important, as a change in the gene sequence can alter phenotype. Also, translocation can occur. This is where a chromatid becomes deleted and rejoins on a different position on the chromosome, or joins a new chromosome. The final type of chromosome mutation that can occur is duplication, where a whole sequence of the chromatid is repeated, therefore resulting in a repetition of the gene sequence. This can lead to new species forming as the genotype is changed in some way that alters the phenotype. This can lead to reproductive isolation therefore, new species can form.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#3
Whole sets of chromosomes can be changed or exchanged. Polyploidy is where an organism has an additional set of chromosomes. This can arise where gametes become diploid and are self fertilised. It can also occur where whole sets of chromosomes double after fertilisation. This can lead to sterile hybrids such as a donkey and horse cross. Hybrids are formed when two organisms of differing chromosomes are mated. This leads to allopolyploidy where the hybrid can have a diploid divide to a haploid chromosome number evenly. Non disjunction can occur where chromosomes fail to separate during anaphase in meiosis. This can be fatal because the gametes have one extra or one less chromosome therefore not all genetic information provided to make new organisms, or if there is too much information, the organism is disabled in someway. However, all of this may lead to new species forming as there is an altered genotype. If the genotype is changed, the phenotype is changed. This leads to an increase in the variation of the population, therefore any changes over time lead to an increase of allelic frequency in the gene pool. This combined with selection pressures favouring one set of alleles over another, coupled with forms of isolation mechanism can lead to speciation.


The Periodic Table- Guitardude19

Here we go with the periodic table:

The first number is the relative atomic mass.
The second number is the atomic number.

Period One

H (1,1) Hydrogen - Group 1
He (4,2) Helium - Group 0

Period Two

Li (7,3) Lithium - Group 1
Be (9,4) Beryllium - Group 2
B (11,5) Boron - Group 3
C (12,6) Carbon - Group 4
N (14,7) Nitrogen - Group 5
O (16,8) Oxygen - Group 6
F (19,9) Flou(censor)rine - Group 7
Ne (20,10) Neon - Group 0

Period Three

Na (23,11) Sodium - Group 1
Mg (24,12) Magnesium - Group 2
Al (27,13) Aluminium - Group 3
Si (28,14) Silicon - Group 4
P (31,15) Phosphorus - Group 5
S (32,16) Sulphur - Group 6
Cl (35.5,17) Chlorine - Group 7
Ar (40,18) Argon - Group 0

Period Four

K (39,19) Potassium - Group 1
Ca (40,20) Calcium - Group 2
Sc (45,21) Scandium - Transition
Ti (48,22) Titanium - Transistion
V (51,23) Vanadium - Transistion
Cr (52,24) Chromium - Transistion
Mn (55,25) Manganese - Transistion
Fe *Pause* (56,26) Iron - Transistion
Co *Pause* (59,27) Cobolt - Transistion
Ni (59,28) Nickle - Transistion
Cu (63,29) Copper - Transistion
Zn (65,30) Zinc - Transistion
Ga (70,31) Gallium - Group 3
Ge (73,32) Germanium - Group 4
As (75,33) Ar(censor)senic - Group 5
Se (79,34) Selenium - Group 6
Br (80,35) Bromine - Group 7
Kr (84,36) Krypton - Group 0

Period Five

Rb (86,37) Rubidium - Group 1
Sr (88,38) Strontium - Group 2
Y (89,39) Yttrium - Transistion
Zr (91,40) Zincronium - Transistion
Nb (93,41) Niobium - Transistion
Mo (96,42) Molybdenium - Transistion
Tc (99,43) Technetium - Transistion
Ru (101,44) Ruthenium - Transistion
Rh (103,45) Rhodium - Transistion
Pd (106,46) Palladium - Transistion
Ag (108,47) Silver - Transistion
Cd (112,48) Cadmium - Transistion
In (115,49) Indium - Group 3
Sn (119,50) Tin - Group 4
Sb (122,51) Antimony - Group 5
Te (128,52) Tellerium - Group 6
I (127,53) Iodine - Group 7
Xe (131,54) Xenon - Group 0

Period Six

Cs (133,55) Caesium - Group 1
Ba (137,56) Barium - group 2
La (139,57) Lanthinium - Lanthanide
Ce (140,58) Cerium - Lanthanide
Pr (141,59) Praseodymium - Lanthanide
Nd (144,60) Neodymium - Lanthanide
Pm (147,61) Promethium - Lanthanide
Sm (150,62) Samarium - Lanthanide
Eu (152,63) Europium - Lanthanide
Gd (157,64) Gadolinium - Lanthanide
Tb (159,65) Terium - Lanthanide
Dy *Pause* (163,66) Dysprosium - Lanthanide
Ho (165,67) Holmium - Lanthanide
Er (167,68) Erbium - Lanthanide
Tm (169,69) Thulium - Lanthanide
Yb (173,70) Ytterbium - Lanthanide
Lu (175,71) Lutetium - Lanthanide
Hf (179,72) Hafnium - Transistion
Ta (181,73) Tantalum - Transistion
W (184,74) Tungsten - Transistion
Re (186,75) Rhenium - Transistion
Os (190,76) Osmium - Transistion
Ir (192,77) Iridium - Transistion
Pt (195,78) Platinum - Transistion
Au (197,79) Gold - Transistion
Hg (201,80) Mercury - Transistion
Tl (204,81) Thalium - Group 3
Pb (207,82) Lead - Group 4
Bi (209,83) Bismuth - Group 5
Po (210,84) Polonium - Group 6
At (210,85) Astatine - Group 7
Rn (222,86) Radon - Group 0

Period Seven

Fr (223,87) Francium - Group 1
Ra *pause* (226,88) Radium - Group 2
Ac (227,89) Actinium - Actinide
Th (232,90) Thorium - Actinide
Pa (231,91) Protactinium - Actinide
U (238,92) Uranium - Actinide
Np (237,93) Neptunium - Actinde
Pu (244,94) Plutonium - Actinide
Am (243,95) Americium - Actinide
Cm (247,96) Curium - Actinde
Bk (247,97) Berkelium - Actinide
Cf (251,98) Californium - Actinide
Es (252,99) Einsteinium -Actinide
Fm (257,100) Fermium - Actinide
Md (258,101) Mendelevium - Actinide
No (259,102) N(Censor)obelium - Actinide
Lr (260,103) Lawerencium - Actinide
Rf (261,104) Rutherfordium - Transistion
Db (262,105) Dubrium - Transistion
Sg (263,106) Seaborgium - Transistion
Bh (262,107) Bohrium - Transistion
Hs (265,108) Hassium - Transistion
Mt (266,109) Meitnerium - Transistion
Ds (262,110) Darmstadtium - Transistion
Uuu (272,111) Ununumium - Transistion (Rg Roentgenium)
Uub (277,112) Ununbium - Transistion
Uut (-,113) Ununtrium - Group 3 (Undiscovered)
Uuq (289,114) Ununquadium - Group 4
Uup (-,115) Ununpentium - Group 5 (undiscovered)
Uuh (-,116 Ununhexium - Group 6 (undiscovered)
Uus *pause* (-,117) Ununseptium - Group 7 (undiscovered)
Uuo (-,118) Ununoctium - Group 0 (undiscovered)
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#4
Organic Chemistry Basics- Guitardude19

In this article I will post what organic chemistry is, how we name the molecules, how they react, and why they react . Have fun reading it. Its going to be very long and hopefully enjoyable.

Organic chemistry has far and wide reaching benefits to the world. Organic chemistry refers to hydrocarbons. Hydrocarbons are molecules that contain carbon and hydrogen. These can be found in oil. Carbon atoms have the ability to bond to themselves infinitely because they have four electrons in their outer shell. This means that a hydrocarbon chain can have one carbon atom, or a million carbon atoms (and more). This unique ability for carbon to bond to itself infinitely means that there are over 10 million known hydrocarbon molecules.
Having so many molecules poses a problem. How do you name them? Well, the first thing you need to know is its chain length. Here is a list of the prefixes for a carbon chain:

A single carbon atom is termed Meth-
Two carbon atoms are termed Eth-
Three carbon atoms are termed Prop-
Four carbon atoms are termed But-
Five carbon atoms are termed Pent-
Six carbon atoms are termed Hex-
Seven carbon atoms are termed Hept-
Eight carbon atoms are termed Oct-
Nine carbon atoms are termed Non-
Ten carbon atoms are termed Dec-

The suffix of a hydrocarbon is the functional group. A functional group is the region at which the reaction occurs. A hydrocarbon that has varying chain lengths but has the same functional group belongs to a homologous series. A homologous series is just a way of classifying similar molecules because they all react the same way (but at different rates because the long the chain the less likely it is to react due to stearic hindrance. Stearic hindrance is where a reaction does not proceed because the molecules cannot come together because atoms on the molecule block them from coming into contact).

Here is a list of all the prefixes:

A hydrocarbon chain with no double bonds between the carbons is termed -ane. C-C.

A hydrocarbon chain with any amount of double bonds between any carbon atoms is termed -ene. C=C.
Incidentally it must be noted that if more than one double bond exists in a chain, the double bond cannot come directly after another double bond because there will be electron repulsions that make the chain unstable. The bonds are unstable because the pi bond extends upwards and two extended bonds create large repulsions. C=C=C-C cannot happen but C=C-C=C can happen.

A hydrocarbon with an oxygen double bonded to one carbon atom that is bonded to two other carbon atoms either side are termed -one. C-C(O)-C. These molecules are known as ketones. These cannot occur at the end of the chain because there will be an extra bond left.

A hydrocarbon chain with an oxygen at the end of the chain and a hydrogen on the end of the chain is termed - al. These are known as aldehydes. C(O)H These occur at the end of the chain because the oxygen is double bonded to the carbon atom.

A hydrocarbon chain with a hydroxy group is termed -ol. C-OH These are known as alcohols .

A hydrocarbon chain with a hydroxy group on the end of a chain with a double bonded oxygen at the end of a chain are termed -oic acid. COOH These can only be found at the end of a carbon chain because the oxygen is double bonded to the carbon. These molecules are known as carboxylic acids.

A hydrocarbon chain with a cyano group on them are termed nitriles CºN. These are found on the end of chains because the carbon nitrogen bond is triple bonded.

A hydrocarbon chain with an amino group C-NH2 are termed amines.

A hydrocarbon chain with an amino group and a double bonded oxygen, both at the end of a chain are called amides CONH2.
A hydrocarbon chain with any halogen atom bonded to it is termed -ide for example chloride bromide iodide and flouride. C-Cl C-Br C-I

A hydrocarbon chain with a double bonded oxygen at the end of a chain with a chloride ion bonded to them are termed acid chlorides COCl.

An alcohol and a carboxylic acid can react to form an ester (acid chlorides also react in the same way to form an ester. Amides react to form esters that are known as secondary amides. These will be dealt with later. Esters are COC(O)C.

Now we have the prefixes, we can name our molecules. If we have a three carbon chain with no double bonds and an OH group on the end of the chain we call this molecule Propanol. (Ethanol is the alcohol in all alcoholic drinks).

However, that alcohol group can go anywhere on the chain. We name them by adding a number to the carbon it is bonded to. So if the OH group is bonded to the second carbon on our three carbon chain we call it proan-2-ol.

The same is true with double bonds. If we have a double bond in a five carbon chain and it is between carbon two and three, we can either name it pent-2-ene or pent-3-ene. The usual way to do this is to take the lowest number, so we call this molecule pent-2-ene.

If we have more than one functional group on our molecule, we name it first by the functional group with the highest molecular mass and then list the other groups alphabetically with their numbers respective to the carbon atoms they are bonded to.

If we have a six carbon chain with a carboxylic acid group at the end of the chain and a OH group on carbons 3 and 4, we call this 3,4 di hydroxy hexanoic acid. The di is added to show that there are two hydroxy groups.
If you have three of the same group, it is called tri, four is tetra. These are independent of the groups so they do not count as the alphabetical naming system, only the functional groups are named alphabetically.

So you can have 1,2,3,4 tetra chloro 5,9 di hydroxy 6,7,8 tri iodo decane.
(That is one funky molecule).

Now we come on to side chains. Side chains are named as numbered suffixes as follows

A single carbon branched chain is called methyl
A two carbon branched chain is called ethyl
A three carbon chain is called proply
Basically you add -yl to the prefix to make it a suffix.
(-yl is also used to name esters which will be explained later on).

So if we have a seven carbon chain with a methyl group on the fourth carbon we call it 4 methyl hepatane.

Hydrocarbons undergo many types of reactions. Before I go on to those, I will explain why they react but in order for you to understand this I will explain electro negativity.

Electro negativity is a property that all atoms have that relates to its ?electron pulling power.? This refers to all chemical reactions because it helps to explain why things react. Basically, a metal has a low electro negativity because it wants to lose its electron to gain a full outer shell. A non metal wants to gain an electron to get a full outer shell. What determines this is the force of attraction of the nucleus to the electron on another atom. Small high charged anions have a high electro negativity because they are able to exert a greater force on a metals electron than a larger anion. This is because a small atom has less shells of electrons and can therefore exert a greater force. A large anion has more shells of electrons than a smaller one so it will therefore experience more shielding and therefore exert less of force on an electron on a metal. Also, in covalent compounds electro negative atoms distort the electron cloud around the less electro negative atom. This leads to polarisation of the bond which makes the highly electronegative atom partially negative and the less electo negative atom partially positive/

However, we assign these atoms with a number. Flourine is very electro negative and is given a EN value of 4. Oxygen is 3.5 and nitrogen is 3 and chlorine is 3 carbon is 2.5 and hydrogen is 2.1. The higher the EN value the stronger its pull for electrons.

This relates to organic chemistry because the EN values explain how distorted a molecule is by the atoms that are bonded to them. Alkanes are composed of carbon and hydrogen (saturated hydrocarbons) only and will not react with anything because there is very little polarisation.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
Last edited by Guitardude19 at Jul 17, 2006,
#5
The other major factor in reactions is charge distribution on a molecule which can be largely due to EN values of the respective atoms. However, alkenes (unsaturated hydrocarbons) can react with many ions because the double carbon bond is partially negative. Partial charges attract ions of the opposite charge so now we need to classify our reactions. The reactions are classified by the type of species that are going to react with our molecule. There are three types, a nucleophile, an electrophile and a free radical.

A nucleophile is a species with lone pairs of electrons that attack positive centres on a hydrocarbon chain.

An electrophile is a species with a electron deficiency and attacks centres of positive charge.

A free radical is a species with a single unbounded electron that attack centres of positive charge.

The type of reactions that molecules undergo are substitution, addition, condensation (can be called dehydration), hydrolysis and combustion.

A nucleophillic substitution reaction is where a nucleophile replaces a group on a hydrocarbon chain.
A nucleophillic addition reaction is where a nucleophile is added to a hydrocarbon chain.
An electrophillic addition reaction is where an electrophile is added to a hydrocarbon chain.
A condensation reaction is where water is removed from a molecule. (Esterfication reactions are special case and I will explain them later in the article).
A hydrolysis reaction is where water is added to a molecule.
Combustion is where oxygen reacts with a molecule to create oxygen based compounds (water and carbon dioxide).
Free radical substitution is where a free radical substitutes itself onto a molecule.

Now lets look at specific reactions that under each of the above.

Nucleophilic susbstitution reaction:

Ethanol + Hydrogen Bromide à Bromoethane + Water.

In this reaction, the hydroxy group polarises the carbon to which it bonds. The hydrogen bromide has charges induced on it because the partial positive charge on the carbon pulls the electron cloud on the bromine. This causes the bromine to be pulled into the carbon. The electrons on the bromine repel the electrons on the hydroxy group causing the bond to break. The hydrogen on the hydrogen bromide is repelled off the molecule and bonds to the hydroxide ion and forms water.

Nucleophilic addition reaction:

Propanal + hydrogen cyanideà 2-hydroxy butanitrile

The oxygen on the carbon causes the carbon to become partial positive and the cyanide ion bonds to the carbon and breaks one of the bonds on the oxygen, giving a negative charge to it. The hydrogen from the hydrogen cyanide is attracted to the negatively charged oxygen creating a hydroxy group.

Electrophilic addition reaction:

Propene + Bromine à 1,2 di bromo propane.

These occur on alkenes where the double bond is partially positive. The partial negative charge on the bond can induce partial positive charges on any species.

Condensation reaction:

Basically anything where water is formed when two molecules come together. A special type of condensation reaction is estification. I will cover this later because estification reactions don?t always produce water.

1 amino butanoic acid + 1 amino butanoic acid à Butanoyl butanamide + water.

Butanoyl butanamide is a secondary amide because the amino group bonds two carbon chains together.

The above is actually an estification reaction because it can continue to react with itself for ever and ever if there were enough of the molecules, which is a form of polymerisation.

Another estification reaction can occur between alcohols and carboxylic acids.

Ethanol + ethanoic acid à Ethyl ethanoate + water

This reaction is reversible. The reverse of this is the hydrolysis reaction.

Another estification reaction occurs between acid chlorides and alcohols. This yields hydrochloric acid instead of water.

Ethanoyl chloride + ethanol à ethyl ethanoate + hydrochloric acid.

This reaction is not reversible because the hydrochloric acid is a gas and leaves the container (read my article on equilibria on the first few pages to get to know reversible reactions).

Naming esters isn?t so easy. An oxygen bonds two carbon chains together and one of the chains also has a double bonded oxygen that originates from the acid. So the part of the chain that was originally the alcohol is termed -yl and the part of the chain that was the acid is termed -oate. So two carbons on each chain gives ethyl ethanoate.

Free radical substitution reaction:

This is a very bad way of making polymers because they make low density plastics. This means that the free radical attacks anywhere on the carbon chain to add another chain to it making it pack badly in a crystal hence low density plastics are weak.

However the reaction goes thus.

Butane + Chlorine + ultraviolet light à 1 chloro butane up 1 tri chloro 2, 3 di chloro 4 tri chloro butane + hydrochloric acid.

Usually when this reaction proceeds, the free radical creates other free radical hydrocarbon chains that attack any partial charge because the free electron has a full charge instead of its partial charge.

Combustion reactions:

Any hydrocarbon undergoes combustion to create carbon dioxide and water. Any amines or amides or anything with a halogen will create pure nitrogen or pure halogen atoms.

Now to some general reactions where we use other compounds to make useful compounds.

If we want to make an alcohol we can take a hydrocarbon with halogen atom on it and react it with sodium hydroxide and warm it.

So if we have 1 bromo pentane and react it with sodium hydroxide, we make a primary alcohol called pentanol. A primary alcohol is when the hydroxy group is bonded to a carbon that is bonded to one other carbon.

Now if the halogen atom is on the second carbon, we have 2 bromo pentane, when we react that with sodium hyrdroxide, we get pentan-2-ol and we get a secondary alcohol. A secondary alcohol is when the hydroxy group id bonded to a carbon that is bonded to two other carbons.

If we had an branched chain of our five carbon chain where the hydroxy group was bonded to a carbon which is bonded to three other carbons, we would have a tertiary alcohol.

So 2 methyl butan-2-ol is made from the reaction of sodium hydroxide and 2 bromo 2 methyl butane.

Now if we oxidise our alcohols, we can get ketones and aldehydes depending on what apparatus we use to oxidise it with. The compound used to oxidise alcohols is acidified potassium dichromate.

A primary alcohol in distillation apparatus creates an aldehydes.
A primary alcohol in reflux apparatus creates a carboxylic acid. If we react the carboxylic phosphorus pentachloride we would create an acid chloride and hydrochloric acid which would be identified as steamy white acidic fumes.
A secondary alcohol in either reflux or distillation apparatus will create a ketone. A ketone is an oxygen that is bonded to a carbon that is bonded to two other carbons so cannot be oxidised further because all four bonds are used.
A tertiary alcohol cannot be oxidised because all four bonds around the carbon are used.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#6
There as an orange to green colour change when alcohols are oxidised. This is because the chromate ion is reduced and therefore its electron transition creates a green colour.

We can reduce carboxylic acids and aldehydes back to alcohols by use of lithium aluminium hydride in dry ether.

If we react ketones and aldehydes with cyanide ions we can create alcohols again. A reaction with an aldehydes creates a primary alcohol and a reaction with a ketone creates a secondary alcohol.

Now that we have seen basic alcohol reactions, lets look at basic nitrogen containing reactions.

If we react bromo ethane with hydrogen cyanide, we get propanitrile and hydrogen bromide. We can react the propanitrile with lithium aluminium hydride to create an amine. We can react our amine with hydrochloric acid to make it more soluble in water (the NH2 group becomes an ion of NH3 plus).

Another thing we can do with nitriles is that if we react then with hydrochloric acid and a bit of water, we can turn them into carboxylic acids.

If we have an acid chloride, and react it with ammonia, we from an amide. These amides can undergo estification and polymerisation reactions to make secondary amides. With the use of tetra phosphorous deca oxide we can dehydrate them into nitriles.

Amides can undergo Hoffman degradation reactions, where they are degraded into amines. To do this, you need some bromine and sodium hydroxide. You make a methyl amine and sodium carbonate with some sodium bromide and water.

Next we will cover basic reactions of aldehydes and ketones. They both react with hydrogen cyanide to make alcohols. If we had an aldehyde, it would make a primary alcohol. If it was a ketone that the cyanide reacted with, it would make a secondary alcohol.

To test whether we have an aldehyde or a ketone, we would use 2,4 di nitro phenyl hydrazine in phosphoric acid and ethanol.. It would give a yellow precipitate if either an aldehyde or ketone was present. To further distinguish between them, we could react the solution with alkaline aminical silver nitrate solution. If the aldehyde is present, then a silver mirror is formed in the solution. If not, you have a ketone. Another method to test for an aldehyde is Fehlings solution. This oxidises the aldehyde and reduces the copper solution to copper oxide. So you get a blue to brick red colour change.

The last test is the iodoform test. You add iodine and sodium hydroxide to your solution. It gives a yellow precipitate and an antiseptic smell. The problem with this test is that it also works on methyl alcohols. So if you have an alcohol on the end of a chain, it will test positive for that too. So not a good way to distinguish them.

The very last part of organic chemistry that I will delve into is Grignard formation. We have seen that when a more electro negative atom reacts with a carbon, it distorts the electron cloud around the species and causes the carbon atom to become partially positive. We can make a carbon atom more negative if we react them with metals. However, only a certain type of metal and a certain type of hydrocarbon will work.

If we have a halo alkane, and we react it with magnesium in dry ether, we get an unstable intermediate known as a Grignard reagent. This is reagent is magnesium bromide bonded to the carbon chain (only if the halo alkane was a bromo alkane).

The great thing about this is that it can react with aldehydes to form primary alcohols and ketones to form secondary alcohols. Not only that, we can make chains very long with these since we can cause a deca alkane with a Grignard on it to react with another molecule of the same length to make a twenty carbon long chain. Also, with the right reagents, we can make very very long ester polymers that can withstand high temperatures, have a lot of strength and are ductile.

Just to add, to make a Grignard, the ether had to be dry because water creates an alkene and magnesium iodo hydroxide.

Now we have reached the end of the article. If you have any questions, feel free to ask. I hope you have enjoyed reading it.

----------------------------

There are some articles to get this thread started. Let the science begin!
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#7
I took physics best part of it was about waves, motion, and sound. Everything else was a bore.
Quote by caughtinamosh
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#8
Eh? I didn't listen in Science from Year 9 onwards, and I still managed to stay in top group, and I;m predicted to pick up a B at GCSE in August.
#9
wuts anti-matter? i heard my physics teacher talking about it and it sounded interesting but i didnt understand the concept. will someone enlighten me?
rawwwwwwwwwwww
#12
Quote by Mr. Raw
wuts anti-matter? i heard my physics teacher talking about it and it sounded interesting but i didnt understand the concept. will someone enlighten me?



All matter is comprimised of a nucleus that contains positively charged protons and neutral neutrons. Orbiting in around the nucleus are electrons (although a theory suggests that electrons behave as stationary waves due to the fact that any spinning charge creates a magnetic field and radiation is emitted- therefore any electron must be "stationary" in a wave motion).

Anyway, anti matter is where positrons (positive electrons) orbit a negative nucleus. Matter and anti matter annihalate to form pure energy gamma rays.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#13
one time in science class my teacher said something and it was wrong and i corrected him and i got in trouble.
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#14
Quote by Sir-Shoelace
one time in science class my teacher said something and it was wrong and i corrected him and i got in trouble.

Thats happend to me quite a few times.
Why are teachers such dicks?
Is there a scientific backing of this?
I must research!
This is what you get.
This is what you get.
This what you get when you mess with us.
#15
Hey, I like the concept. Don't think I'll write up anything big like that, but if anyone has any questions I'd be glad to take them, particularly in physics. It is a broad subject though, so I may not be totally up on every topic.

Howabout some topic to discuss...how bout that ITER they're building in France? Biggest experiment to test the feasibility of nuclear fusion as an energy source.

Sounds interesting, I hope they're able to come up with a method of creating energy in a safe way. One interesting use I heard was to use fusion plants to eventually supply energy for hydrogen production for fuel, rather than fusion for everything.
#16
There is already an abundant energy source that has been realized, NUCLEAR fission. The problem is dealing with the waste, and the Chernobyl effect. Devise a way to neutralize the radioactive danger, and the waste problem is solved. I think there will come a time where we can alter the structure of these "radioactive" fuels in such a way as to prevent critical mass from being accomplished, thus in effect solving the Chernobyl dilemma. High Hopes!!
Last edited by havocrus at Jul 17, 2006,
#17
Has anyone read or heard about the book The Road to Reality by Roger Penrose? I just got it and its like a 1000 page tomb about theoretical physics and stuff. Ive been reading it but the first half is all math which you need to understand the second half. Its pretty crazy.
Originally Posted by guitar_freak333
I dont like death metal, I just see it as a bunch of hairy men playing the same riff over and over again exetremely fast.
#18
Quote by Ipster
Hey, I like the concept. Don't think I'll write up anything big like that, but if anyone has any questions I'd be glad to take them, particularly in physics. It is a broad subject though, so I may not be totally up on every topic.

Howabout some topic to discuss...how bout that ITER they're building in France? Biggest experiment to test the feasibility of nuclear fusion as an energy source.

Sounds interesting, I hope they're able to come up with a method of creating energy in a safe way. One interesting use I heard was to use fusion plants to eventually supply energy for hydrogen production for fuel, rather than fusion for everything.



ITER is a very important step forward in the quest for new energy sources and I hope the political wrangling around where it should be sited (now in France) does not turn into some form of energy arms race where one country will try and out compete with the other, hindering any advancement for new energy sources.

The international community needs to look into projects like ITER and help fund such projects since there is a world energy crisis. Also, governments need to look into and invest heavily in nuclear power since it is safe. (Chenobly was a rare disaster- Lessons have hopefully been learnt).

The only problem with ITER is that within that magnetic feild to hold the plasma, any circulating charge will be giving off immense radiation therefore its sheilding is immense- if it is breached what are the consequences? Hopefully the experimental ITER will unlock the answer safely without disaster.

ITER faces one challenge- the plasma it will create is highly unpredicatable therefore any fusion that occurs is short lived and causes the plasma to become unstable. ITER hopes to find solutions to that problem. Hopefully, ITER will unlock new understanding of plasma behaviour and maybe scientists can create models for small scale fusion reactors such as ITER.

I really do think ITER is an exciting prospect for our future energy demands. Hopefully it is funded for as long as needs be and we can come one step closer to building alternate energy supplies.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#19
^

Well, I don't think they're gonna be changing the site any more, I think there was a deal worked out so that Japan, the other country that wanted it, got some incentives package.

I'm really hoping this works out, because this is pretty much the final test for nuclear fusion. If it doesn't work out after all the money these countries have poured in, it'll probably be the end of fusion for quite a while.

Quote by havocrus
There is already an abundant energy source that has been realized, NUCLEAR fission. The problem is dealing with the waste, and the Chernobyl effect. Devise a way to neutralize the radioactive danger, and the waste problem is solved. I think there will come a time where we can alter the structure of these "radioactive" fuels in such a way as to prevent critical mass from being accomplished, thus in effect solving the Chernobyl dilemma. High Hopes!!


Fusion, if it can be attained in a safe manner, will essentially eliminate the waste problem. The half life of the waste from fusion is much less, it'll decay to something safe within about a decade, if I remember correctly. Also, with a large enough, self-sustaining fusion reaction we can potentially get more energy than we put in. As for the Chernobyl effect...I'm not familiar with that, or are you just referring to the Chernobyl disaster? As far as that goes, it's not gonna happen again, modern fission plants.


Oh, on another note, I found an interesting link regarding higher dimensions, and a way to think about them. Clicky!
#20
Quote by Ipster
Well, I don't think they're gonna be changing the site any more, I think there was a deal worked out so that Japan, the other country that wanted it, got some incentives package.

I'm really hoping this works out, because this is pretty much the final test for nuclear fusion. If it doesn't work out after all the money these countries have poured in, it'll probably be the end of fusion for quite a while.


I just hope governments have more sense in scienctific investment. Should ITER not deliver on fusion, hopefully world governments will fund a similar project. They cant give up on one concept if it goes wrong (since it is the first of its kind [although there have been similar fusion experiments, nothing on this scale though] it cant be expected to run smoothly).

Also, the link you posted... great site, I ll need to read it in more detail.

Quote by havocrus
There is already an abundant energy source that has been realized, NUCLEAR fission. The problem is dealing with the waste, and the Chernobyl effect. Devise a way to neutralize the radioactive danger, and the waste problem is solved. I think there will come a time where we can alter the structure of these "radioactive" fuels in such a way as to prevent critical mass from being accomplished, thus in effect solving the Chernobyl dilemma. High Hopes!!


You cant alter the structure of any atom to avoid critical mass in radioactive fuels. In order to change its structure to remove the threat of critical mass, you would need to remove a lot of sub atomic particles, which would in turn change the element to something that is not radioactive- which defeats the purpose of our nuclear reactor.

Also, Chenobly was a one off. People need to stop bringing that up as a reason not to have nuclear power. With modern reactors we are safer than ever.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
Last edited by Guitardude19 at Jul 18, 2006,
#22
Quote by thesublime
www.popsci.com <----- FTW


That site looks good I ll add links to the front page. Thanks for that.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#23
I think I'm going to be in this thread a lot if people start posting more. Anyway, what do you people think about aliens or E.T. life on other planets or moons, or galexies billions of lightyears away we haven't even discovered yet? I personally think it might be possible. So what do you people think?
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#24
The possibility of life is certainly there. There are so many galaxies out there, there must be a few planets capable of developing life. We're here, aren't we?

I think the chances that aliens are visiting us and probing us are much lower, the closest stars are quite far away. A few billion years more advanced than us, who knows what kind of tech is possible though? I think the sci-fi geek in me wants to see some sort of (hopefully friendly) extraterrestrial contact, but I know that's pretty much not gonna happen.

I am interested in seeing if there might be some small amounts of life in our solar system. I remember hearing about a mission to Europa, which is mainly water/ice and may have some primitive life. Anyone know more about that?
#25
Dr. Frank Drake developed an equation for calculating the probability of human life based on the chances of worlds similar to ours recreating.



R* is the rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is average number of planets that can potentially support life per star that has planets
fl is the fraction of the above that actually go on to develop life
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of the above that are willing and able to communicate
L is the expected lifetime of such a civilization

The values he put into the equation were:

R* = 10/year,
fp = 0.5, (probably exagerrated, I would say WAY less stars have planets)
ne = 2,
fl = 1,
fi = 0.01,
fc = 0.01,
L = 10,000 years.

Even if you used values lesser than his, the answer is way > 1. Of course, even with thousands of civilizations, the distances are so huge that it's unlikely they have or will visit us any time soon.
لا إله إلا الله محمد رسول الله
#26
Life on other planets is possible. Meteorites, asteroids and comets are known to carry amino acids. Upon collision with larger solar bodies, the amino acids can form peptide chains (the theory of how life was triggered). If it happened to earth, there is a possiblility that the same sequence of events happened on other earth like planets.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#28
Quote by Ipster
Hey, I like the concept. Don't think I'll write up anything big like that, but if anyone has any questions I'd be glad to take them, particularly in physics. It is a broad subject though, so I may not be totally up on every topic.

Howabout some topic to discuss...how bout that ITER they're building in France? Biggest experiment to test the feasibility of nuclear fusion as an energy source.

Sounds interesting, I hope they're able to come up with a method of creating energy in a safe way. One interesting use I heard was to use fusion plants to eventually supply energy for hydrogen production for fuel, rather than fusion for everything.


sounds interesting, but my scientific hypothesis based on previous results is that the french will **** it up
#29
science is cool.


no really, i did pretty well on my chem and bio AP tests (5s on both). physics i understood, but could've done a LOT better. then again i didn't try at all this year, got an A, and just passed my AP. and i'm beginning studies in electrical engineering in...exactly a month


Quote by Ipster
George Bush vetoes stem cell research bill. Thoughts?

Bush uses one of his first (maybe his first and only veto throughout his entire presidency...) to restrain scientific progress. problem? yes. science should be monitored to ensure it doesn't propagate beyond the constraints of what humans can control, but it also shouldn't be restrained and controlled by people who know little to nothing of it and its potential impact on society and the future of human life as a whole.
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Phobos (he oozes cool)


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#30
That ten dimensions site is really cool. I liked it alot.

I'm very uneducated when it comes to science, but I love every thing about it.
Quote by guitar?

BTW do not say n-i-g-g-e-r. I know some one who said lets go buy some snickers and some black guy punched him in the face.
#31
so they say we only use 10 percent of out brain and I remeber like a couple months ago a friend of mine showed me this site, had to do with popping your frontal lobes and accessing the rest of your brain something like that if I remember correctly, does anyone know what I am talking about, is there any justification to the whole popping your frontal lobes.
anybody wanna put anything here just let me know
#32
Quote by Ipster
George Bush vetoes stem cell research bill. Thoughts?



I cant believe he did that. He obviously does not understand the full potential of stem cell research, or he is bringing in his religious beliefs.

Of course we need some moral ethics when it comes to research involving human life, but if president Bush is using his religion to veto something, then stem cell research is in a dire state.

Religion and politics should be kept seperate from science since they hinder it, not maintain nor control it.

It is up to the scientific community to set its own guidelines and it should not need to pander to any political or religious group. Stem cell research has the potential to cure many debilitating illnesses and diseases. I do not care for the arguement "ESC's can create another human life." That arguement has no basis. It is a non arguement because not all embryos develop- in order for that arguement to stand you must make the assumption all embryos will develop into a human life, but since this is not the case, it can be disregarded.

Embryonic stem cells are biological break through and all the researchers in thi field need as much funding and governmental backing as possible. However, with president Bush vetoing the stem cell research bill, this field has been knocked back to square one. The potential of this field is too great for one president to veto it on his own "moral and religious" beliefs if that is the case as I am sure it is.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#33
Quote by societies_worm
so they say we only use 10 percent of out brain and I remeber like a couple months ago a friend of mine showed me this site, had to do with popping your frontal lobes and accessing the rest of your brain something like that if I remember correctly, does anyone know what I am talking about, is there any justification to the whole popping your frontal lobes.



Im not sure about this whole popping your frontal lobes- they are responsible for higher functions to do with behaviour, impulse control, socalisation and other higher responses. Damage to them results in dampaned responses, agression, unable to interact with people, intellegence greatly reduced and so on (personality changes).

It is true that we use only 10% of our brain for higher thinking and conscious thought since the brains primary role is to keep the body in balance (it monitors and changes the internal environment to keep it in equilibruim), howerver, you can train your brain to make it more efficient but off hand I dont know you do it.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#34
If there is a religion thread sticky and a politics thread sticky..... why cant.....

*Looks with puppy dog eyes* Please!
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#35
You spelled science wrong in your sig

I do agree a stickied science thread would be great, if we can get good debates and a fair few people to contribute.
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#36
So, science masters, what do you think about the man on UG who is trying to stay up for 120 hours? (See pit thread)
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#37
He will eventually fall asleep before that 120 hours is up. Even if its just for a few minutes...he probably wont even notice.
#38
I'm in highschool and ive been taking all of the advanced chemistry and physics classes. I'm mostly interested in physics and i was thinking of getting a degree in physics in university. I like astronomy so i was thinking of getting a degree in astrophysics but i don't know a lot about it.
To anyone who knows more about astrophysics...please explain.
#39
If he is mentally strong enough to stay up 120 hours good for him but I predict he will feel ill, sick, possibly hallucinate, he will have sore eyes, difficultuy in breathing, be extremely tired, low energy, lathargic, slow, and he will have lower heart rate.


Also, Thanks for pointing out that I spelt "science" wrong in my sig. Highly embarrassing.
Sat in a lab, curing diseases. They actually LET me play with chemicals!
#40
Yeah, I like this thread, could be very interesting.

I have a decent amount of knowledge on all three main areas of science (high grade GCSE at minimum) with Physics being my specialty (A level standard with keen interests) so I'll do my best to answer nay question people may have.
There is poetry in despair.