Aldehydes and Ketones Flashcards
1
Q
why is a primary alcohol heated under distillation to prepare an aldehyde
A
- distillation seperates the aldehyde from the oxidising agent
- and hence prevents further oxidation of the aldehyde to a carboxyllic acid
2
Q
describe a chemical test, which can be used to distinguish between an aldehyde and a ketone
A
Add tollens reagent - if a silver mirror is produced then its an aldehyde, if not its a ketone
3
Q
what happens if an aldehyde or ketone undergoes nucleophilic addition
A
- a (K)CN- nucleophile attacks them
- a hydroxynitrile is formed
- can give rise to optical isomers
4
Q
suggest a reason why KCN is used instead of HCN
A
- HCN and KCN are toxic gases
- HCN is weak/ KCN dissocited better than HCN
5
Q
what are aldehydes and ketones reduced to
A
- aldehydes are reduced to primary alcohols
- ketones are reduced to secondary alcohols
6
Q
what are the reagents and conditions of nucleophilic addition for reduction
A
reagents: sodium tetrahydridoborate, NaBH4
conditions: solvent is water, warm aqeuous solution
7
Q
why is NaBH4 a suitable reducing agent carbonyl compounds
A
the BH4- ions from NaBH4, provides hydride ions, :H-, which act as a nucleophile
8
Q
A
