Question

Write the structures of A, B, and C in the following sequence of reactions: (a) \(\text{CH}_3\text{COOH} \xrightarrow{\text{SOCl}_2} A \xrightarrow{\text{H}_2, \text{Pd-BaSO}_4} B \xrightarrow{\text{H}_2\text{N-NH}_2} C\)
(b) \(\text{CH}_3\text{CN} \xrightarrow{1.\text{DIBAL-H}} A \xrightarrow{2.\text{H}_2\text{O}} B \xrightarrow{\Delta} C\)

Hint:

These reactions show the versatility of organic reagents in modifying functional groups, including thionyl chloride for acylation, DIBAL-H for nitrile reduction, and the use of hydrazine for carbon-carbon bond formation.

Answer 1

(a) The first reaction is the conversion of acetic acid (\(\text{CH}_3\text{COOH}\)) to acetyl chloride (A) using SOCl$_2$ (thionyl chloride). The structure of A is: \[ \text{A} = \text{CH}_3\text{COCl} \] Next, the acetyl chloride (A) undergoes hydrogenation in the presence of palladium on barium sulfate (Pd/BaSO$_4$) to give the product B, which is ethane (\(\text{C}_2\text{H}_6\)). The structure of B is: \[ \text{B} = \text{CH}_3\text{CH}_3 \] Finally, B undergoes the reaction with hydrazine (\(\text{H}_2\text{N-NH}_2\)) to form the product C, which is hydrazine. The structure of C is: \[ \text{C} = \text{H}_2\text{N-NH}_2 \] (b) The second set of reactions involves the reduction of acetonitrile (\(\text{CH}_3\text{CN}\)) with DIBAL-H (diisobutylaluminum hydride) to form the imine A. The structure of A is: \[ \text{A} = \text{CH}_3\text{CH}=\text{NH} \] Next, upon hydrolysis with water, A forms the aldehyde B, which is acetaldehyde. The structure of B is: \[ \text{B} = \text{CH}_3\text{CHO} \] Finally, B undergoes heating (represented by \(\Delta\)) to give C, which is acetic acid. The structure of C is: \[ \text{C} = \text{CH}_3\text{COOH} \]