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GATE 2022 CY – Question 13

Organic Chemistry · Experimental Techniques in Organic Chemistry: Optical rotation (polarimetry). Application of various chromatographic techniques such as thin-layer, column, HPLC and GC. Applications of UV-visible, IR, NMR spectroscopy and Mass spectrometry in the structural determination of organic molecules. · 1 mark · Multiple choice

The major product in the given reaction is Q. The mass spectrum of Q shows {[M] = molecular ion peak}

Diagram for GATE 2022 CY question 13
  1. [M], [M+2] and [M+4] with relative intensity of 1:2:1
  2. [M] and [M+2] with relative intensity of 1:1
  3. [M], [M+2] and [M+4] with relative intensity of 1:3:1
  4. [M] and [M+2] with relative intensity of 2:1

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Correct answer: (A) [M], [M+2] and [M+4] with relative intensity of 1:2:1

Explanation

Corey–Fuchs dibromoolefination replaces the aldehyde oxygen with a CBr2 alkene terminus. Two bromines, each with nearly equal 79Br/81Br abundance, give three isotope combinations with coefficients(1+z)².

Thus **M, M+2, M+4 in 1:2:1, A**.