JEE Advanced · 2020 · 27 Sep 2020 · Paper 1 · General Organic Chemistry

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Newman projections P, Q, R and S are shown below:

Which one of the following options represents identical molecules?

(A)P and Q
(B)Q and S
(C)Q and R✓ Correct
(D)R and S

Answer: (C)

Solution

Converting each Newman projection to its IUPAC name:

P: 2,3,3-trimethylpentan-2-ol

Q: 3-ethyl-2-methylpentan-2-ol

R: 3-ethyl-2-methylpentan-2-ol

S: 3-ethyl-2-methylpentan-3-ol

Comparing the structures, Q and R have the same IUPAC name and are therefore identical molecules. They differ only in their Newman projection representation (different conformations of the same molecule).

JEE Advanced · 2020 · 27 Sep 2020 · Paper 1 · Single correct option

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