Question

(A)- Write a note on the wolf - kishner reduction.
(B)- Boiling points of carboxylic acids are higher than aldehydes and ketones of comparable molecular masses. Why?
(C)- Draw a dimer structure of ethanoic acid in vapor state.

Answer 1

Hint: (A)- As the name of the reaction suggested that the wolff – kishner reaction is a reduction reaction in which aldehyde & ketone reduced to the alkane.
(B)- Boiling point of most stable & strong compounds is always high.
(C)- Dimer structure is that structure in which two same molecules are present in one structure.

Complete step by step answer:
(A)- Short note on the wolff - kishner reduction reaction is as follow:
-In the initial mechanism of above reaction, ketone or aldehyde reacts with hydrazine to form hydrazone and the solvent used in this reaction is generally diethylene glycol.
      

-In the latter step in the presence of basic medium final product alkanes are obtained and nitrogen gas is evolved.
           

(B)- Boiling point of carboxylic acid $\left(\text{ - COOH}\right)$ is higher than aldehyde $\left(\text{ - CHO}\right)$ and ketone $\left(\text{ - CO}\right)$ because the molecular weight of carboxylic acid is more than both given functional groups, so we want more energy to break that molecule.
(C)- Ethanoic acid is also known as acetic acid it is present in dimer form in the vapour phase due to the presence of hydrogen bond between two units of ethanoic acid.
     

Note: In the above question you should be clear about each concept that is used in the above three points and don’t get confused in any of them. And also you should be clear in the chemical formula of functional groups.