Question

Ozonolysis of an organic compound gives formaldehyde as one of the products. This confirms the presence of
(A) two ethylenic double bonds
(B) a vinyl group
(C) as isopropyl group
(D) an acetylenic triple bond

Answer 1

Hint: Ozonolysis mechanism proceeds via an oxidative cleavage reaction. The ozone not only breaks the carbon pi bond but also the carbon-carbon sigma bond. It involves the attack of ozone on the given reactant to form an ozonide.

Complete step by step answer: Ozonolysis is an organic reaction where the unsaturated bonds of alkenes, alkynes, or azo compounds are cleaved with ozone. Alkenes and alkynes form organic compounds in which the multiple carbon–carbon bond has been replaced by a carbonyl group while azo compounds form nitrosamines.

Presence of one vinyl (or ethenyl) group gives formaldehyde as one of the products in ozonolysis. CH2=CH- on ozonolysis will give HCHO.The formation of ozonolysis product involves formation of ozonide intermediate. Ozonide is highly unstable and explosive so it is reduced in situ by use of zinc metal.

Hence option B is the correct answer.

Note: The steps of ozonolysis are as follows:
1.The electrophilic addition of ozone to the carbon-carbon bond forms the molozonide intermediate which is quite unstable. Due to this unstable nature, the molozonide continues reacting – breaking apart to form a carbonyl molecule and a carbonyl oxide molecule.
2.The carbonyl molecule and the carbonyl oxide molecule formed in step 1 rearrange themselves, reforming to create a more stable ozonide intermediate. This ozonide intermediate can be subjected to either an oxidative workup or a reductive workup. The oxidative workup will give carboxylic acid as the product whereas the reductive workup will yield aldehydes or ketones.