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Amines
2017 Paper Two
Question Eleven
Looking at past AQA A-level Chemistry questions, I wanted to go beyond the answers and focus on thought processes, ideas and tips that will help in examinations.
The series will help you to spot weaknesses and help with revision, or it can serve as addenda to your notes.If you haven't gone through the paper, please look up the questions at www.aqa.org.uk, or click the direct link below, and have a go...
AQA A-level CHEMISTRY Paper 2 Organic and Physical ChemistryMonday 19 June 2017
The base strength has everything to do with the lone pair on the nitrogen - how available the lone pair is.
For E, the nitrogen is next to the ring and the nitrogen's lone pair is delocalised into the ring - the lone pair is less available for donation.
The lone pairs on the nitrogens in G and F are more available - they are next to alkyl groups so benefit from the positive inductive effect of these groups.
For F, the nitrogen's lone pair is the most available - furthest away from the ring.
The amines can be ranked in order of increasing base strength: E<G<F
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Step 1
Chlorine and ultraviolet light to form C6H5CH2Cl
Step 2
KCN alcoholic & aqueous producing C6H5CH2CN
Step 3
Hydrogen gas with a nickel catalyst, or LiAlH4 in dry ether.
Notes
1 is a free radical substitution
2 nucleophilic substitution (the cyanide salts are soluble in water, while the benzyl chloride isn't. Therefore, ethanol is added so that both reagents are slightly soluble and the reaction proceeds)
3 Reduction
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