Dear sir

i have following doubts

1. why acid chlorides are not reduced by diborane while carboxylic acids can be reduced.

2. why alpha hydroxy ketones give tollen's test.

3. Nucleophilic substitution on ester are easy with respect to carboxylic acid while alkoxide ion is a poor leaving group than hydroxide ion.

Hydroxy acetone reduces ammoniacal silver nitrate ( Tollen's reagent), thereby  being oxidised to DL- lactic acid. Althogh ketones do not normally reduce Tollen's reagent or Fehling's solution, alpha hydroxy ketones are exceptions. Similarly, ketones form phenyl hydrazone with phenyl hydrazine, but alpha hydroxy ketones form osazones. This is because alpha hydroxy ketone appears to exist as an equilibrium mixture of hydroxy ketone and cyclic hemiacetal forms ( ring-chain tautomerism ).