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