Question

What happens when (Give chemical equations only): (i) Acetaldehyde reacts with dilute NaOH:

Hint:

In aldol condensation, an enolate ion forms and attacks the carbonyl carbon of another molecule, leading to β-hydroxy aldehyde or ketone formation.

Answer 1

When acetaldehyde reacts with dilute sodium hydroxide (NaOH), an aldol condensation reaction takes place, leading to the formation of β-hydroxy aldehyde (acetaldol): \[ \text{CH}_3\text{CHO} + \text{NaOH} \rightarrow \text{CH}_3\text{CH(OH)CHO} \]
(ii) Acetone is heated with solid barium hydroxide: % Solution
Solution:
When acetone is heated with solid barium hydroxide, it undergoes aldol condensation, forming mesityl oxide: \[ 3\text{CH}_3\text{COCH}_3 \xrightarrow{\text{Ba(OH)}_2} \text{CH}_3\text{COCH}_2\text{COCH}_3 \, (\text{mesityl oxide}) \]
(iii) Formaldehyde reacts with concentrated NaOH solution: % Solution
Solution:
When formaldehyde reacts with concentrated sodium hydroxide, it undergoes the Cannizzaro reaction, forming formate and alcohol: \[ 2 \text{CH}_2\text{O} + \text{NaOH} \rightarrow \text{HCOONa} + \text{CH_3OH} \]
(iv) Acetic acid reacts with ethanol in the presence of H\(_2\)SO\(_4\): % Solution
Solution:
When acetic acid reacts with ethanol in the presence of sulfuric acid, it undergoes esterification to form ethyl acetate (an ester): \[ \text{CH}_3\text{COOH} + \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{H}_2\text{SO}_4} \text{CH}_3\text{COOCH}_2\text{CH}_3 \]
(v) Acetaldehyde reacts with phenyl hydrazine: % Solution
Solution:
When acetaldehyde reacts with phenyl hydrazine, it forms an aldol condensation product known as hydrazone: \[ \text{CH}_3\text{CHO} + \text{C}_6\text{H}_5\text{NH-NH}_2 \rightarrow \text{CH}_3\text{CH=N-NH}_2 \]