JEE Advanced 2022 — Paper 2 — CHEM-I solution

JEE Advanced2022Paper 2CHEM-I

The total number of chiral molecules formed from one molecule of P on complete ozonolysis (O $_{3}$ , Zn/H $_{2}$ O) is ________.

Your answer

Solution

Complete reductive ozonolysis cleaves every C=C of P. The cleavages occur at six C=C bonds, generating seven fragments along the chain.

Working through the symmetric structure:

From each terminal $(C H_{3})_{2} C = C H (C H_{3})$ end one obtains acetaldehyde (CH $_{3}$ CHO) — achiral.

The fragments adjacent to the chiral C(OH)(CH $_{3}$ ) centers become $α$ -hydroxy 1,2-diketone fragments. Two of the resulting fragments are simple symmetric diketo compounds (achiral) and two are $α$ -hydroxy ketoaldehyde fragments that retain the stereogenic carbon bearing the OH and CH $_{3}$ ; these are the chiral pieces.

The central fragment from the symmetric middle portion is achiral by internal symmetry.

Counting unique chiral molecules among the products: 2.

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