Which is the only compound which can be completely ruled out as a product of the reaction of 1,3-butadiene with HCl?
A)(S)-3-chloro-1-butene
B)(R)-3-chloro-1-butene
C)(E)-1-chloro-2-butene
D)(Z)-1-chloro-2-butene
E)(Z)-2-chloro-2-butene

Question

Quizplus · Accepted Answer

The reaction between 1,3-butadiene and HCl can lead to the formation of several different products, depending on the regio- and stereochemistry of the addition. The potential products are:
- (S)-3-chloro-1-butene
- (R)-3-chloro-1-butene
- (E)-1-chloro-2-butene
- (Z)-1-chloro-2-butene
- (Z)-2-chloro-2-butene

However, only the formation of (Z)-2-chloro-2-butene can be completely ruled out as a product of the reaction. This is because the addition of HCl to 1,3-butadiene occurs via a syn mechanism, which leads to cis-addition. Therefore, the product must have a cis stereochemistry, ruling out the formation of (Z)-2-chloro-2-butene, which has a trans stereochemistry.

Therefore, the best choice is E.

Which Is the Only Compound Which Can Be Completely Ruled