Question

In Cannizzaro reaction given below :
$2 PhCHO \xrightarrow{: OH ^{-}}PhCH _{2} OH + PhCOO ^{-}$ the slowest step is

• A. the attack of : $OH^-$ 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 $PhCH _{2} O ^{-}$.

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.