Chapter 28 - Amines
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what makes amines useful as intermediates
they are very reactive
how do you decide whether an amine is primary, secondary or tertiaryu
count the n umber of alkyl groups on it. 1 is primary, 2 is secondary, 3 is tertiary
what shape are amines
pyramidal with bond angles 107
why are the boiling points of amines lower than those of comparative alcohols
because the hydrogen bonds between amine molecules are lower than those between alcohol molecules because nitrogen is less electronegative than oxygen
describe the solubility of different types of amines in water
smaller amines are more soluble, primary and secondary amines are much more soluble than tertiary amines phenylamine isnt very soluble
what kinds of behaviours does the lone pair on amines allow
lets the amine act as a base by accepting a proton can bond with an electron deficient carbon when acting as a nucleophile
what do amines form with acids
ionic salts, in an acid base reaction
why will phenylamine (which is almost insoluble) dissolve in excess HCl
because it will form a phenylammonium chloride salt, which is water soluble
what does the base stength of amine depend on
the availablility of the lone electron pair
how do aliphatic and aromatic amines and ammonia compare in strength
aliphatic are stronger than ammonia and ammonia is stronger than aromatic
what kind of aliphatic amines are the strongest and why
tertiary amines because the electron releasing (inductive) effect of the alkyl groups increases the electron density around the nitrogen which increases the availability of the lone pair
why are aromatic amines the weakest bases
because the lone pair becomes delocalised ijnto benzenes ring which decreases its availability
how do amines react with halogenoalkanes
in a nucleophilic substitution reaction
what is produced when amines react with halogenoalkanes and why
a mixture of primary secondary tertiary amines and a quaternary ammonium salt because further substitution occurs
what 2 routes are there to produce amines
reduction of nitriles and nucleophilic substitution of haloalkanes
why is reduction of amines preferred to nucleophilic substitution of haloalkanes in amine synthesis
because only the desired amine is produced
what are the 2 steps (with equations) in the reduction of nitriles to form amines
1: RBr + CN- —–> RCN + Br- 2: RCN + 4[H] —-> RCH2NH2
what are the conditions of the 2 steps in the reduction of nitriles to form amines
1: aqueous ethanol 2: Ni (catalyst)/ H2 (reducing agent)
what are the 2 steps to make phenylamine
1: make nitrobenzene from benzene via electrophilic substitution 2: reduction to phenylamine using tin and HCl
what is the economic importance of amines
used in the manufacture of synthetic materials such as nylon and polyurethane, dyes and drugs
how are N-substituted amides made
through acylation (addition-elimination) using an amine and an acyl chloride
how are quaternary ammonium salts used in industry
in the manufacture of hair and fabric conditioners
how do quaternary ammonium salts in conditioners work
wet fabric/hair picks up negative charge, so the positive cations form a coating which prevents the build up of static electricity