Question

In Cannizzaro reaction given below :
$2PhCHO\stackrel{:O{H}^{-}}{\to }PhC{H}_{2}OH+PhCO{O}^{-}$ the slowest step is

• A. the attack of : $O{H}^{-}$ at the carbonyl group
• B. the transfer of hydride to the carbonyl group
• C. the abstraction of proton from the carboxylic group
• D. the protonation of $PhC{H}_2{O}^{-}$.

Answer 1

Answer: (B)

Rate determining step is always the slowest step. In case of Cannizzaro reaction, $H^{-}$ - transfer to the carbonyl group is the rate determining step and hence the slowest step.