2019 HydrocarbonsReactions of Alkenes – Ozonolysis and Markovnikov Addition of HCl Hard Question 23 of 75 in Hydrocarbons

An alkene 'A' on reaction with $O_3$ and Zn-$H_2O$ gives propanone and ethanal in equimolar ratio. Addition of HCl to alkene 'A' gives 'B' as the major product. The structure of product 'B' is:

A $Cl-CH_2-CH_2-CH(CH_3)_2$
B $H_3C-CH_2-CH(CH_2Cl)-CH_3$
C $H_3C-CH_2-C(CH_3)(Cl)-CH_3$
D $H_3C-CH(Cl)-CH(CH_3)-CH_3$

The answer is C.

Solution

Ozonolysis of A gives propanone and ethanal in equimolar ratio, so A is $(CH_3)_2C=CH-CH_3$ (2-methylbut-2-ene). Addition of HCl follows Markovnikov's rule: $H^+$ adds to the CH carbon to give the more stable 3° carbocation, and $Cl^-$ attaches to it. B: $H_3C-CH_2-C(CH_3)(Cl)-CH_3$ (2-chloro-2-methylbutane)

Concept identifying an alkene from ozonolysis products

Hydrocarbons in past papers

75 questions from this chapter have appeared across 26 exam years.