JEE Main 2021 · 24 Feb · Shift 1 · Chemistry Q40

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ChemistrySingle correct+4 / -1Question 40 of 90

Which of the following compound gives pink colour on reaction with phthalic anhydride in conc. H $_2$ SO $_4$ followed by treatment with NaOH ?

4-Propylphenol

2-Propylphenol

4-Methyl-6-propylbenzene-1,3-diol

Option C: a resorcinol (two OH meta to each other) carrying a methyl and a propyl group.

4-Methyl-5-propylbenzene-1,2-diol

Option D: a catechol (two adjacent OH) carrying a propyl and a methyl group.

Answer and worked solution

Official answer: B

Phthalein test. A phenol with a free para position condenses with phthalic anhydride to a phenolphthalein-type dye, pink in NaOH. 2-Propylphenol qualifies; in 4-propylphenol the para position is blocked.

(B)

Topics:Phenols Detection of functional groups

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JEE Main 2021 · 24 Feb · Shift 1, Chemistry question 40