Question

The 1,2-dibromide is synthesized from an alkene starting material. Draw the alkene starting material.

a) CH₂=CH₂
b) CH3-CH=CH₂
c) CH3-CH₂-CH=CH₂
d) CH3-CH₂-CH₂-CH=CH₂

Answer 1

The alkene starting material for synthesizing a 1,2-dibromide upon reaction with bromine is CH3-CH2-CH=CH2 (1-butene), which would result in 1,2-dibromobutane.

Step-by-step explanation:

The question asks which alkene starting material would synthesize a 1,2-dibromide upon reaction with bromine. When an alkene reacts with bromine (Br2), a vicinal (1,2-) dibromide is formed. This can be identified through the anti-addition mechanism where two bromine atoms add to the carbon atoms involved in the double bond of the alkene.

Choosing between the options provided:

CH2=CH2 (ethene)

CH3-CH=CH2 (propene)

CH3-CH2-CH=CH2 (1-butene)

CH3-CH2-CH2-CH=CH2 (1-pentene)

The correct starting material for creating a 1,2-dibromide would be option (c) CH3-CH2-CH=CH2 (1-butene) since its structure allows for the direct addition of bromine across the double bond to form 1,2-dibromobutane.