[figure] Compound (X) is subjected to the sequence of reactions as shown above. Molar mass of the major product (Y) formed is g mol-1. (Given molar mass in g mol-1 C : 12, H : 1, O : 16 )
- 90
- 118
- 160
- 125
Answer
(2) 118
Solution
(i) Br2/CHCl3: addition to the side-chain C=C ⇒ vicinal dibromide, C6H5CHBr-CH2Br
(ii) Excess NaNH2: two dehydrobromination steps give phenylacetylene; the extra NaNH2 removes the acidic terminal H ⇒ sodium phenylacetylide, C6H5C C Na
(iii) CH3I: alkylation of the acetylide ⇒ C6H5C C-CH3 (1-phenylpropyne)
(iv) Na/liquid NH3 (Birch reduction): anti addition of hydrogen ⇒ trans-alkene, C6H5CH=CH-CH3 = (Y)
[figure]
(Y) = C9H10 ⇒ M = 9 × 12 + 10 × 1 = 118 g mol-1
Answer: (2)