6.2.1 Amines Flashcards
(21 cards)
what are amines
organic compounds derived from ammonia (NH3) where 1 or more of the hydrogen atoms has been replaced by a carbon chain or ring
what are aliphatic amines
where the N is attached to at least 1 straight or branched carbon chain, an alkyl chain R
what are aromatic amines
where the N is attached to an aromatic ring, an aryl group Ar
where do you find amines
commonly occur in nature and have many effects on the body- e.g. serotonin as a neurotransmitter
how can amines be classified
- primary: where the N has one carbon, alkyl or aryl, group attached to it, NH2 (R)
- secondary: where the N has two carbons attached to it, NH (R, R’)
- tertiary: where the N has 3 carbons attached to it, N (R,R’,R’’)
how do you name primary amines
- if the NH2 is present qat the end of a chain, can use suffix -amine to the name of the alkyl chain attached to, e.g. CH3H2NH2 would be ethylamine
- if the NH2 is attached to any other carbon other than carbon-1, can use prefix amino , e.g. CH3CHNH2CH2CH3 is 2-aminobutane
how do you name secondary and tertiary amines
- if containing the same alkyl group, can use prefixes di- and tri-, e.g. (CH3)2NH = dimethylamine
- when 3 or more different groups attached, need to name using N-linked
- smaller group is N-linked of the bigger group, and ORDERED ALPHABETICALLY
- e.g. CH3CH2C-N-CH3-CH2CH3 = N-ethyl-N-methylpropylamine
how do amines react
behave as bases, as contain a lone pair of electrons on the N:, and can accept a hydrogen (proton)
how do amines react with proton
form a dative covalent bond
- e.g. CH3CH2-N:H2 + H+ → [CH3CH2NH3]+
how do amines react to form salts
act as bases and neutralise acids to make salts
- a + goes on the N, and the -ve metal ion goes nearby
- e.g. 2CH3-NH2 + H2SO4 → (CH3N+H3)2SO4-
how is a primary amine formed
haloalkane + :NH3 → ammonium halide salt + H2O
- excess ammonia
- ethanol as a solvent
why can ammonia be used to react with a haloalkane and form an amine
- has a lone pair of electrons on the :NH3
- can act as a nucleophile in a substitution reaction with haloalkane
- produces an ammonium salt
- add aqueous alkali to generate the amine from the salt
what is the 2 step mechanism of forming a primary amine
haloalkane + :NH3 → ammonium salt
ammonium salt + NaOH → amine + sodium salt + H2O
what is the two step mechanism of the formation of propylamine from 1-chloropropane
CH3CH2CH2Cl + NH3 → CH3CH2CH2NH3+Cl-
CH3CH2CH2NH3+Cl- + NaOH → CH3CH2CH2NH2 + NaOH + H2O
why is ethanol needed to form an amine
- acts as a solvent
- prevents substitution of haloalkane by water
- which would form an alcohol
why is excess ammonia needed to form an amine
prevents the further substitution of the amine group, to 2° and 3°
how do you form a secondary amine
primary amine + haloalkane
- just a further substitution, as the N in the amine formed still contains a lone pair
- continue again for tertiary
how would you form dipropylamine from 1-chloropropane
CH3CH2CH2Cl + CH3CH2CH2:NH2 → CH3CH2CH2-NH-CH2CH2CH3 + NaCl + H2O
- still via forming the salt first, and then reacting with NaOH
what is an aromatic amine
benzene ring with at least one N attached, e.g. NH2
how do you form an aromatic amine
via reduction of nitrobenzene:
1) nitrobenzene is heated under reflux with tin and conc. hydrochloric acid
2) forms the ammonium salt phenylammonium chloride
3) the salt is then reacted with excess NaOH, to form the aromatic amine phenylamine
what is the equation for formation of phenylamine
⌬-NO2 + 6[H] → ⌬-NH2 + 2H2O
- with Sn/conc. HCl on arrow as reducing agents
- and excess NaOH(aq) on bottom
