On the Action of Ozone on Polyynes and Monocyanopolyynes: Selective Ozonolysis of Polyynes

Abstract

Ozone reacts selectively with hydrogen‐terminated polyynes when they are present in a mixture with monocyanopolyynes. The latter class of molecules reacts more slowly with ozone. Since the ozone attack to double or triple bonds is essentially electrophilic in its nature, the lower reactivity with ozone of monocyanopolyynes has been interpreted in terms of lower π‐electron charge concentration at the conjugated triple bonds because of the electron‐withdrawing effect exerted by the nitrile group at one end of the monocyanopolyynes molecules. This experimental result demonstrates the presence of conjugation among adjacent triple bonds in the polyynes molecules: the electron‐withdrawing effect of the –CN group propagates along the entire polyyne chains.

Keywords:

• Polyynes
• monocyanopolyynes
• cyanopolyynes
• ozone
• ozonolysis
• electrophilic addition
• electron‐withdrawing
• triple bonds conjugation