Which of the following compounds on reductive ozonolysis will give two molecules of \(\mathrm{CH}_{2}(\mathrm{CHO})_{2} ?\) (a) 1,3 -cyclohexadiene (b) 2,4 -hexadiene (c) 1,4 -cyclohexadiene (d) 1-Methyl-1,3-cyclopentadiene

Reductive ozonolysis is a reaction that involves the cleavage of carbon-carbon double bonds in alkenes or dienes using ozone. The process is followed by a reduction using a reducing agent, such as zinc or dimethyl sulfide. The purpose of reductive ozonolysis is to convert double bonds into carbonyl groups (aldehydes or ketones).

Let's analyze each given compound and determine the reductive ozonolysis products. (a) 1,3-cyclohexadiene The ozonolysis on 1,3-cyclohexadiene would cleave both the double bonds, resulting in two carbonyl compounds connected in a chain. However, these products are not \(\mathrm{CH}_2(\mathrm{CHO})_2\) molecules. (b) 2,4-hexadiene The ozonolysis of 2,4-hexadiene would cleave both the double bonds, but the resulting products are different from \(\mathrm{CH}_2(\mathrm{CHO})_2\) molecules. (c) 1,4-cyclohexadiene The ozonolysis of 1,4-cyclohexadiene cleaves the double bonds and produces an open-chain product. However, this product does not consist of two \(\mathrm{CH}_2(\mathrm{CHO})_2\) molecules. (d) 1-Methyl-1,3-cyclopentadiene The ozonolysis of this compound would cleave both the double bonds. Each cleaved bond would form a double bond to oxygen, resulting in two \(\mathrm{CH}_2(\mathrm{CHO})_2\) molecules. Hence, the correct answer is:

(d) 1-Methyl-1,3-cyclopentadiene.