Question

Explain why:

(1) Acetaldehyde undergoes aldol condensation but formaldehyde does not.

(2) Acetic acid is a weaker acid as compared to formic acid.

Answer 1

(1) This is because acetaldehyde has α - H-atom whereas formaldehyde does not have α-H-atom.

 

(2) This is due to + I effect of a methyl group (CH₃-)

Acetic acid 

\[\begin{array}{cc}\\
\ce{O}\phantom{..}\\
||\phantom{..}\\
\ce{CH3-C-O-H}\
\end{array}\]

Formic acid

 \[\begin{array}{cc}\\
\phantom{....}\ce{O}\\
\phantom{....}||\\
\ce{H-C}\\
\phantom{.....}\backslash\\
\phantom{.......}\ce{O}\\
\phantom{.........}\backslash\\
\phantom{...........}\ce{H}\\
\end{array}\]