amines, amino acids and polymers
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amines are derived from…
ammonia
2 types of amines
aliphatic aromatic
aliphatic amine
nitrogen attached to at least one straight or branched carbon chain
aromatic amine
nitrogen attached to at least one aromatic carbon ring
why do amines behave as bases?
lone pair of electrons on N atom can accept a proton, forming dative covalent bond
amine + acid ->
salt and water
formation of primary aliphatic amines
• ammonia (nucleophile) undergoes substitution reaction with haloalkane, producing ammonium salt • ammonium salt then reacted with excess ammonia to generate amine
conditions required for formation of primary aliphatic amines
• ethanol as solvent to prevent further substitution of haloalkane with water to produce alcohols • excess ammonia used to reduce further substitution of amine group to form secondary + tertiary amines
2 overall stages for formation of primary aliphatic amines
• salt formatin - amine formation
formation for secondary and tertiary amines
• primary amine reacted with haloalkane, and undergoes substitution as it still has a lone pair of electrons on N
2 overall stages for formation of secondary and tertiary aliphatic amines
• salt formation - amine formation
production of aromatic amines
• form ammonium salt by reacting nitrobenzene under reflux with tin + HCl • react w excess NaOH to produce phenylamine
why is methylamine a stronger base than ammonia?
• alkyl group (-CH3) pushes electrons away, making the charge on the N more negative, therefore meaning H-ions can be attracted more easily • ion formed is more stable, as alkyl group spreads positive charge through molecule
why is phenylamine a weaker base than ammonia?
• lone pair on N touches and partially dissociates into electron ring of phenol, and becoming delocalised with them, meaning the pair cannot fully combine with H-ions, intensity of charge is decreased • if lone pair joins to H-ion, there must be a disruption in delocalisation (making the molecule more unstable) which requires energy + doesn’t occur easily
amino acid
substance containing both amine and carboxylic acid functional groups
how many amino acids in the body
20
what is an α-amino acid
an amino acid where amine group is attached to α-carbon (2nd carbon atom, next to carbonyl group)
general amino acid formula
RCH(NH2)COOH
why do amino acids have reactions similar to both acids and amines?
because they contain both carb. acid and amine functional groups
3 main reactions of amino acids
• w. HCl • w. aqueous alkalis • w. alcohols
product of reaction between amino acid and HCl
ammonium salt
product of reaction between amino acid and aqueous alkali
salt and water
product of reaction between amino acid and alcohol
ester and water
amide
product of reaction between acyl chloride w. ammonia and amines