Before You Begin

Question #44378

Difficulty: 8/10 | 🟢 Free

The Question

1,2-Dimethylcyclopentene is subjected to oxymercuration using $\ce{Hg(OAc)2}$ in an aqueous medium at 298 K to form an organomercurial intermediate $X$ (prior to demercuration). Which of the following statements correctly describes the relative stereochemistry of the substituents in the major product $X$ ?

Options

A.
The $\ce{-OH}$ and $\ce{-HgOAc}$ groups are \textit{trans}; the two $\ce{-CH3}$ groups are \textit{trans}.
B.
The $\ce{-OH}$ and $\ce{-HgOAc}$ groups are \textit{trans}; the two $\ce{-CH3}$ groups are \textit{cis}.
C.
The $\ce{-OH}$ and $\ce{-HgOAc}$ groups are \textit{cis}; the two $\ce{-CH3}$ groups are \textit{trans}.
D.
The $\ce{-OH}$ and $\ce{-HgOAc}$ groups are \textit{cis}; the two $\ce{-CH3}$ groups are \textit{cis}.

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Oxymercuration-Demercuration Specificity|Optical Activity and Enantiomers

Why This Question Is Tricky

Common Mistakes

Students often memorize that oxymercuration is an anti-addition, correctly identifying that the incoming nucleophile ( $\ce{-OH}$ ) and the electrophile ( $\ce{-HgOAc}$ ) will be trans to each other.

However, they frequently fail to visualize the 3D spatial consequences on the existing substituents of the alkene.

Because the two methyl groups are 'cis' (coplanar) in the starting 1,2-dimethylcyclopentene, students intuitively assume they remain cis in the product.

They overlook that the $S_N2$ -like anti-attack of water on the bridged mercurinium ion causes an inversion of configuration at the attacked carbon.

This inversion forces the methyl group at the attacked carbon to the opposite face, resulting in the two methyl groups becoming trans to each other in the final intermediate.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Alcohols, Phenols, and Ethers - Class 12
Concept	Oxymercuration-Demercuration Specificity
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free