Question

Question 13.20 How would you convert the following compounds into benzene?

(i) Ethyne

(ii) Ethene

(iii) Hexane

Class XI Hydrocarbons Page 397

Answer 1

(i) when ethyne is passed through red hot iron tube at 873 K temperature , it trimerises to gives benzene . reaction is shown in figure.

(ii) Ethene is first converted into ethyne and then to benzene as shown figure.

(iii) When vapors of hexane are passed over heated catalyst consisting of Cr2O3 , Mo2O3 and V2O5 supported over Al2O3 at 773K under 10- 20 atm pressure, cyclization and aromatization occurs simultaneously to afford benzene. reaction is shown in figure.