Question

What alkenes would you start with to prepare the following products?

Short answer

a)

b)

c)

d)

Step-by-step solution

Step-by-Step solutionStep 1: Electrophilic addition reactions

The addition of HBr to alkene happens in two steps. They include protonation followed by bromine addition. A carbocation intermediate is also generated in this reaction.

The hydrogen-halogen bond cleaves in the reaction between hydrogen halide and alkene. The bond between hydrogen and fluorine is hard to cleave, so the addition of HF to an alkene is slow when compared to other halides like HCl and HBr.

Alkene required for the preparation of compound (a)

(a)The given product bromocyclopentane can be prepared by reacting cyclopentene with HBr. The reaction can be given as:

Alkene is needed for the preparation of compound (a)

Alkene required for the preparation of compound (b)

(b) The alkene 1-ethyl-1-iodocyclohexane can be produced by reacting 1-ethylcyclohex-1-ene or ethylenecyclohexane with KI and ${\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}$. The reaction can be given as:

Alkene is required for the preparation of compound (b)

Alkene required for the preparation of compound (c)

The given compound 3-Bromohexane can be prepared by reacting 3-Hexene with HBr. The reaction can be given as:

Alkene is required for the preparation of compound (c)

Alkene required for the preparation of compound (d)

The given alkyl chloride, (1-chloroethyl) cyclohexane can be prepared by reacting vinylcyclohexane with HCl. The reaction can be given as:

Alkene is required for the preparation of compound (d)