Question

In the following reaction:
Aldehyde + Alcohol $\stackrel{HCl}{\to }$ Acetal
Aldehyde Alcohol
$HCHO$ ${}^{t}BuOH$
$C{H}_{3}CHO$ $MeOH$
The best combinations is:

• A. $HCHO\text{and}{}^{t}BuOH$
• B. $C{H}_{3}CHO\text{and}{}^{t}BuOH$
• C. $HCHO\text{and}MeOH$
• D. $C{H}_{3}CHO\text{and}MeOH$

Answer 1

The correct option is C $HCHO\text{and}MeOH$

In the above reaction, aldehyde acts as an electrophile and alcohol acts as a nucleophile. For electrophiles, $HCHO$ is more reactive than $C{H}_{3}CHO$. It is due to less steric hinderance and more electron deficient carbonyl carbon in $HCHO$.
rate $\propto \frac{1}{\text{steric crowding of aldehyde}}$

For nucleophiles, lesser the crowding, better is the nucleophilicity. So, $MeOH$ is a better nucleophile than $tBuOH$
Hence, the best combination amomg the given options are:
$HCHO$ and $MeOH$