AQA Chemistry Unit 4 with Anon_98

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NUCLEOPHILLIC SUBSTITUTION MECHANISM BETWEEN BROMOETHANE AND A TERTIARY AMINE(Triethylamine) TO PRODUCE A QUATERNARY AMMONIUM SALT.

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Reply 101

Anon_98

Well, for late night revision, that was getting far too exciting. Anyway, that's basically how you form primary, secondary, tertiary + quarternary amines.

Uses for quarternary amines:

- Cationic surfactants in fabric softeners/conditioners (when at least one of the alkyl groups is a long chain.)

(edited 7 years ago)

Reply 102

Anon_98

Amines – Preparation –Topic 7.

Alright so, another way to produce primary aliphatic amines is by the reduction of nitriles.

For example:

CH3CH2CN + 4[H] --------------> CH3CH2CH2NH2

Reducing agents: LiAlH4 in ether OR H2 with Nickel catalyst.

~

Aromatic amines, on the other hand, can be prepared by the reduction of nitro compounds.

For example:

1,3-dinitrobenzene + 12[H] -----------> 1,3-diaminobenzene + H2O

(I basically cba to draw out the structures of those on a separate post, but they're simple enough)

Reagents: Sn and conc HCl.

Reply 103

Anon_98

Amino acids – Acid, base properties + proteins – Topic 8.

Okay, so the amino acid, alanine, has the structure CH3CH(NH2)COOH and the IUPAC name would be 2-aminopropanoic acid. It also shows optical stereoisomerism.

So, I'm going to draw the alanine species that is neutral in charge below. Basically the zwitterion of alanine:

Reply 104

Anon_98

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Reply 105

Anon_98

I'm using alanine as an example but this can be applied to any amino acid.

Okay, so now I'm going to draw the alanine species at high PH. I.E. basic conditions:

Reply 106

Anon_98

AT HIGH PH.

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Reply 107

Anon_98

Alright, now I'll draw it at low PH. I.E. Acidic conditions.

Reply 108

Anon_98

AT LOW PH.

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Reply 109

Anon_98

Why do amino acids have a high melting point?

In the solid state, amino acids exist as an ionic lattice of zwitterions. To melt the solid, the relatively strong ionic bonds need to be broken which requires a lot of energy.

Reply 110

Anon_98

Amino acids – proteins – Topic 8.

- Proteins are sequences of amino acids joined by peptide links.

- Hydrolysis of the peptide link produces the constituent amino acids.

- Protein chains are often arranged in a helix and the type of interaction that is responsible for holding the protein chain in this shape is hydrogen bonding.

What method can be used to separate a mixture of amino acids formed by the hydrolysis of a protein and how could the various amino acids could be identified?

Alright so, mixtures of amino acids can be separated by paper chromatography or thin-layer chromatography and to identify the range of amino acids you could compare them with known amino acids. ( the fact there are a limited number helps)

Reply 111

Anon_98

Polymers – Addition polymers – Topic 9.

Alkenes undergo addition polymerisation, and when asked to draw the repeating unit just remember it's only two C-C atoms in a chain then the rest of the molecule, if it's big is basically, like, methyl bonds etc + remember to draw the trailing bonds. I cba to draw example structures bc it's pretty simple.

Reasons as to why polyalkenes are generally non- biodegradable:

- They are chemically inert.

- C-C chain is not easily split by biological entities such as enzymes.

Reply 112

Anon_98

Polymers – Condensation polymers – Topic 9.

Condensation polymerisation - Reaction between monomers having two functional groups and the loss of a small molecule e.g. H₂O

Alright so we need to know two types of polymers: polyesters + polyamides and we need to know the formation of 3 types of them:

Terylene (which is a polyester)

Nylon 6,6 (which is a polyamide)

Kevlar (which is also a polyamide)

~

Alright, so we'll start with Terylene AKA PET - Plastic bottles.

Reactants: Benzene-1,4-dicarboxylic acid AND ethane-1,2-diol.

I'll draw out the reaction below:

Reply 113

Anon_98

Reaction between Benzene-1,4-dicarboxylic acid and ethane-1,2-diol to form TERYLENE.

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Reply 114

Anon_98

Alright, now we'll do Nylon 6,6

Reactants: Hexanedioic acid AND 1,6-diaminohexane

Again, I'll draw out the reaction below:

Reply 115

Anon_98

Reaction between hexanedioc acid AND 1,6-diaminohexane to form NYLON 6,6

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Reply 116

Anon_98

Finally, we'll do Kevlar

Reactants: Benzene-1,4-dicarboxylic acid AND Benzene-1,4-diamine

Below:

Reply 117

Anon_98

Reaction between Benzene-1,4-dicarboxylic acid and Benzene-1,4-diamine to form KEVLAR.

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Reply 118

Anon_98

Polymers – Biodegradability and disposal of polymers – Topic 9.

Polyesters and polyamides are biodegradable bc they can be broken down by hydrolysis and therefore by enzymes.

Advantages and disadvantages of landfill as a method of polymer disposal:

Advantages:

- Acceptable for biodegradable polymers.

- Generation of methane which can be used as a fuel

Disadvantages:

- Suitable sites are being used up in UK.

- Sites are visual pollution.

- Methane is a greenhouse gas.

Reply 119

Anon_98

Advantages and disadvantages of Incineration as a method of polymer disposal:

Advantages:

- Generates heat energy

- Reduces volume of waste.

Disadvantages:

- Toxic gases are produced which need to be dealt with and that's expensive.