amines, amides and amino acids

Amines

When one or more hydrogens in ammonia (NH3) is replaced with an organic group

Quaternary ammonium ion

When ammonia has 4 R groups attached to it and the nitrogen has a positive charge

Basicity of amines

The lone pair on the nitrogen atom can form a dative bond with a positive hydrogen atom. The amine donates a lone pair and accepts a proton

Base

Proton acceptors

Amine salts

Amines are neutralised by acids to make ammonium salts

Ammonium salts e.g.

RNH2 + HCl —> RNH3+Cl-

Naming amine

Suffix-amine(or amine ion) Prefix-organic group attached

How to produce amines

Amines can be made by heating a haloalkane with an excess of ethanolic ammonia (ammonia dissolved in ethanol)

Producing amines example

2NH3 + RBr —> RNH2 + NH4+Br-

Products of producing amines

You’ll get a mix of different products which you can separate with distillation

How to make aromatic amines

First you need to heat a mixture up of a nitro compound, tin metal and concentrated HCl under reflux which produces an aromatic ammonium salt. They you need to add an alkali to the salt to make it an aromatic compound

Armocatic amine example

C6H6N02 + 6[H] —→ 1.Sn,conc HCl,reflux 2.NaOH(aq) C6H6NH2 + 2H20

Amides

Carboxyl derivatives that contain the functional group -CONH2

Why do amides act differently to amines

Because the carbonyl group pulls electrons from the rest of the -CONH2 group

Types of amides

Primary amide- R group attached to carboxylate group (replaces OH)

Secondary amide- R group also attached to nitrogen

Naming amides

Suffix-amide

Primary amides have the prefix of the stem of the longest carbon chain

Secondary amides have an N in front of the whole name

Amino acids

Have two functional groups am amine group (NH2) and a carboxylate group (COOH) attached to an alpha carbon which is attached to a hydrogen and an alkyl group

General formula of an amino acid

RCH(NH2)COOH

Amino acids reactions with alkalis

The carboxyl group in amino acids can react with alkalis to form a conjugate base

General formula of a conjugate base

RCH(NH2)COO- which combines with a positive ion to form a salt

Amino acids reactions with acids

The amine group can react with an acid to form a salt of its conjugate base. They N becomes positive with a negative ion at the front

Formation of esters

The carboxyl group in amino acids can react with an alcohol in the presence of a strong acid catalyst to form an ester. The H in the OH is replaced by an R group a water is also formed

Stereoisomerism

When two molecules have the same structural formula but a different arrangement in space

Optical isomerism

mirror images which are non-superimposable. These have a chiral carbon atom. These are optically active so they rotate plane polarised light. One enantiomer rotates it clockwise the other anti-clockwise

Chiral carbon

A carbon atom with four different groups attached to it

Enantiomers

Usually labelled L or D. Chiral compounds are very common in nature but you usually only find one of the enantiomers

Addition polymers

Double bonds in an allele are broken and then joined together to form a long chain

Monomers

Individual small molecules of an addition polymer (the aliens it forms from)

Condensation polymerisation

Involves two different types of monomers each with two different functional groups. When each link is formed a water molecule is lost

Polyesters

Formed by a dicarboxylic acids and diols. It forms an ester link -COO. Polyester fibres are used in clothing- they’re strong, flexible and abrasion resistant

Polyamides

Formed from dicarboxylic acids and diamonds. Forms an amide link -CONH

Hydrolysis

Adding the h20 molecule back in

Acid and base hydrolysis

using just water for hydrolysis is too slow so an acid or base is used

Polyamides hydrolysis with an acid

Polyamides hydrolyse more easily with an acid catalyst than base. Polyamides + 2nH20 —→ dicarboxylic acid + diammonium salt

Polyester hydrolysis with an acid

Is the same as the hydrolysis except you get a diol instead of a diamine

Hydrolysis of a polyester with a base

Polyesters hydrolyse more easily with a base than acid. Polyester + base —> dicarboxylic acid salt + diol