Amines and polymers Flashcards
Naming primary amines
When the NH2 group is on the end of the chain you can add the suffix -amine to the end of the alkyl chain, i.e. ethylamine. When the amine group is not on the first carbon, the amine is named using the prefix amino and a number is added to indicate the position of the amine group, i.e. 2-aminobutane.
Naming secondary or tertiary amines
When they contain the same alkyl group, you can use the prefex di- or tri- to indicate the number of alkyl groups attached to the nitrogen atom, i.e.e dimethylamine. When two or more different groups are attached to a nitrogen atom, the compound is named as a N-substituted derivative. For example, N-methylpropylamine. For a tertiary amine it might be N-ethyl-N-methylpropylamine
Primary amine
Attached to two hydrogens and a R-group
Secondary amine
Attached to one hydrogen and two R-groups
Tertiary amine
Attached to three R-groups
Aliphatic amine
When the nitrogen atom is attached to at least one straight or branched carbon chain
Aromatic amine
When the nitrogen is attached to an aromatic ring
Amines as bases
Amines behave as bases in chemical reactions as the lone pair of electrons on the nitrogen atom accepts a proton.
What happens when an amine accepts a proton
A dative covalent bond is formed between the lone pair of electrons on the nitrogen atom and the proton
Salt formation with amines
Amines are bases which neutralise acids to make salts
CH3NH2 + HCl –> CH3NH3+Cl-
Formation of primary amine
A haloalkane reacts with ammonia to form an ammonium salt, i.e. propylammonium chloride. This reacts with an aqueous alkali such as NaOH to form an amine, i.e. propylamine. Ethanol is used as a solvent, to prevent any substitution of the haloalkane with water to produce an alcohol. Excess ammonia is used, to prevent further substitutions of the amine group to form secondary and tertiary amines.
Formation of secondary amines
The salt formed when the ammonia reacts with the haloalkanes can react with another haloalkane to form an ammonium salt i.e (CH3CH2CH2)2NH2+Cl-. This reacts with NaOH to form a secondary amine, NaCl and H20
Formation of tertiary amines
From further substitutions of the secondary amine salt
Preparation of aromatic amines
Nitrobenzene is heated under reflux with tin and HCl to form the ammonium salt, phenylammonium chloride. This then reacts with excess NaOH to form phenylamine. Tin and HCl are the reducing agents
Easy way to make an aliphatic amine
React with excess ammonia in ethanol
General formula of an alpha amino acid
RCH(NH2)COOH
Reactivity of amino acids
As they have both the acidic COOH and basic NH2, amino acids have similar reactions to both carboxylic acids and amines and can react with both acids and bases
Reaction of the amine group in amino acids
Will react with acids to form an ammonium salt. When reacting with HCl, the NH2 group turns into NH3+ and Cl- is also formed
Reaction of the carboxylic acid group in amines with an aqueous alkali
Forms a salt and water. For example, when it reacts with NaOH the COOH turns into COO-Na+, water is also produced
Reaction of the carboxylic acid group in amino acids with alcohols
The amino acids are esterified by heating the alcohol in concentrated sulphuric acid. Water is also produced
Amides
Are the product of a reaction between an acyl chloride with ammonia and amines. There is a carbon double bond with an oxygen atom, the carbon is also bonded to a nitrogen
What is required for an optical isomer (amino acid)
Must have a chiral centre, which leads to the existence of two non-superimposable mirror image structures
What’s a chiral centre
A carbon atom which is attached to four different types of atoms
Drawing optical isomers
The two structures are drawn as mirror images of each other
Condensation polymerisation
The joining up of monomers with the loss of water or HCl
Polyesters
Can be made from one monomer containing both a carboxylic acid and an alcohol group, or from two monomers; one containing two carboxylic acid groups and the other containing two alcohol groups. Involves the loss of water
Polyamides
Polyamides can be made from one monomer containing both a carboxylic acid (or acyl chloride) and an amine group, or from two monomers, one containing two carboxylic acid groups (or acyl chloride) and an another containing two amine groups. If a carboxylic acid group is used H2O is produced, if alcyl chloride is used HCl is produced
Hydrolysing condensation polymers
Polyesters and polyamides can be hydrolysed using a hot aqueous alkali such as sodium hydroxide or by hot aqueous acid such as HCl
Acid hydrolyses of polyesters
The monomers are reformed
Alkali hydrolyses of polyesters
The alcohol is reformed, The carboxylic acid group reacts with the alkali to form COO-Na+
Acid hydrolyses of polyamides
The monomers are reformed but it is NH3+ instead of NH2
Alkali hydrolyses of polyamides
The amine is reformed, the carboxylic acid group reacts with the alkali to form COO-Na+
What is specific to an addition polymer
Contains a C=C double bond
Backbone of polymer is a continuous chain of carbon atoms
What is specific to a condensation polymer
Two monomers, each with two of the same functional groups or one monomer with two different functional groups
Polymer contains ester or amide linkage
