Question

The major products M and N formed in the following reaction sequence are

• A. A
• B. B
• C. C
• D. D

Hint:

McMurry coupling converts carbonyl compounds into alkenesAnti addition of Br$_2$ to a trans alkene generally gives a meso product

Answer 1

The Correct Option is D

Step 1: Identify the first reaction.
The reagent TiCl$_3$/Zn-Cu is used for McMurry coupling reactionIn this reaction, two carbonyl compounds couple together to form an alkene

Step 2: Formation of product M.
The given carbonyl compound is acetophenoneOn McMurry coupling, two molecules of acetophenone combine to form 2,3-diphenyl-2-butene
\[ 2\,\text{PhCOCH}_3 \xrightarrow{\text{TiCl}_3/\text{Zn-Cu}} \text{PhC(CH}_3)=\text{C(CH}_3)\text{Ph} \]
The major alkene formed is the more stable trans alkene due to less steric repulsion between bulky phenyl groups

Step 3: Reaction of M with bromine.
The alkene M reacts with Br$_2$ by anti addition across the double bond

Step 4: Stereochemical outcome.
Anti addition of Br$_2$ to trans-2,3-diphenyl-2-butene gives meso-2,3-dibromo-2,3-diphenylbutane

Step 5: Conclusion.
Therefore, M is trans-2,3-diphenyl-2-butene and N is meso-2,3-dibromo-2,3-diphenylbutane
\[ \boxed{\text{D}} \]