IIT-JEE 2012 · Paper 2 · Chemistry Q34

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ChemistrySingle correct+3 / -1Question 34 of 60

Passage

Paragraph for Questions 33 and 34

In the following reaction sequence, the compound J is an intermediate.
$\mathbf I\xrightarrow[\ce{CH3COONa}]{\ce{(CH3CO)2O}}\mathbf J\xrightarrow[\text{(ii) }\ce{SOCl2}\text{ (iii) anhyd. }\ce{AlCl3}]{\text{(i) }\ce{H2},\ \text{Pd/C}}\mathbf K$

J $(\ce{C9H8O2})$ gives effervescence on treatment with $\ce{NaHCO3}$ and a positive Baeyer's test.

The compound K is

Indane: a benzene ring fused to a cyclopentane ring (no carbonyl).

Dihydrocoumarin (chroman-2-one): a benzene fused to a six-membered lactone.

1-Indanone: a benzene fused to a cyclopentanone with the C=O next to the ring.

2-Indanone: a benzene fused to a cyclopentanone with the C=O at the far carbon.

Answer and worked solution

Official answer: C

Steps from cinnamic acid (J):

$\ce{H2}$ , Pd/C reduces the C=C: 3-phenylpropanoic acid.
$\ce{SOCl2}$ : the acid chloride $\ce{C6H5CH2CH2COCl}$ .
Anhydrous $\ce{AlCl3}$ : intramolecular Friedel-Crafts acylation closes a five-membered ring onto the ortho position.

K is 1-indanone (indan-1-one), with the C=O attached to the benzene ring.

(C)

Topics:Aromatic hydrocarbons and electrophilic substitution Acid derivatives

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IIT-JEE 2012 · Paper 2, Chemistry question 34