91Ó°ÊÓ

Alkynes that reside in the middle of the C-C chain are known as internal alkynes and those that reside in any of the ends of the chain are known as terminal alkynes.

Examples are given below:

Internal Alkyne

Terminal alkyne

Alkynes undergo oxidative cleavage when treated with ozone. It leads to cleavage of both sigma and pi-bonds of the alkyne and produces carboxylic acid and carbon dioxide (in case of terminal alkyne).The general reaction scheme is given below:

Oxidative cleavage of the terminal and internal alkyne

a.

Ozonolysis of the internal alkyne gives two carboxylic acid groups

b.

The biphenyl compound reacts with ozone to form 2 moles of benzoic acid

c.

The compound is composed of a terminal as well as an internal alkyne