The number of possible stereoisomers obtained in the following reaction is ____ · ABC26OR0762
Subject: Organic Chemistry · Chapter: Stereochemistry · Topic: Stereochemistry – General · Exam: GATE 2000-2022 · Marks: 2 · Difficulty: Medium
The number of possible stereoisomers obtained in the following reaction is ____ 
Answer
Answer (as printed): 8
The options are missing from the source scan for this question, so there is nothing here for this letter to point at. The letter is what the book printed.
Explanation
Answer: 8 — O₃/Zn cleaves the reactive C9=C10 bond of 4-methylphenanthrene to give 6-methylbiphenyl-2,2′-dicarbaldehyde. Excess PhMgBr turns both CHO groups into CH(OH)Ph, creating two stereocentres; they are non-equivalent because only one ring carries CH₃. The biaryl now has three ortho substituents (CH(OH)Ph and CH₃ on one ring, CH(OH)Ph on the other), so rotation about the aryl–aryl bond is restricted and the axis is a third stereogenic element. 2³ = 8 stereoisomers.
Study loop for Stereochemistry