Exams › JEE Advanced › Chemistry

Consider the following two-step reaction sequence starting from propanoic acid (CH3CH2COOH): Step 1: Treatment with Br2 in the presence of red phosphorus, followed by hydrolysis with H2O, gives compound P. Step 2: Compound P is treated first with NaOH, then acidified with H3O+, giving compound Q along with benzene-1,2-dicarboxylic acid as a by-product. Which of the following statement(s) about P and Q is/are correct?

1. P can be reduced to a primary alcohol using NaBH4.
2. When P is treated with concentrated NH4OH solution followed by acidification, compound Q is obtained.
3. When Q is treated with a solution of NaNO2 in aqueous HCl, nitrogen gas is liberated.
4. P is a stronger acid than propanoic acid (CH3CH2COOH).

Correct answer: When Q is treated with a solution of NaNO2 in aqueous HCl, nitrogen gas is liberated.

Solution

Step 1 (HVZ) converts CH3CH2COOH to 2-bromopropanoic acid (P). Step 2 with NaOH causes SN2 inversion giving 2-hydroxypropanoic acid, i.e., lactic acid (Q). NaBH4 does not reduce -COOH, so statement 1 is wrong; NH4OH on an acid gives amide not lactic acid, so statement 2 is wrong; NaNO2/HCl liberates N2 from primary amines (not -OH), so statement 3 is wrong; alpha-bromo acids are more acidic than the parent acid due to electron withdrawal, so statement 4 is correct.

Related JEE Advanced Chemistry questions

• When hydrogen halides react with alcohols, alkyl group rearrangement does not typically happen with most primary alcohols. What is the most accurate reason for this?
• Which of the following statements accurately describes the behavior of the given compound?
• Tertiary and secondary carbocations readily participate in elimination reactions when treated with strong alkoxide bases, while aryl and vinyl halides resist nucleophilic substitution. Which of the following reactions is correct?
• Although neopentyl alcohol is a primary alcohol, it follows the SN1 mechanism due to steric hindrance caused by a bulky alkyl group. Identify its structure.
• In the following sequence of reactions, identify the structures of intermediates Y, Z, W, and M: Y --(NaBH4)--> Z --(conc. HBr)--> W Y --(N2H4 / KOH, heat)--> M M --(NBS, heat/light)--> W W --(1) Mg/ether, (2) CO2, (3) H3O+)--> Ph-CH(COOH)-CH2-CH3 Which of the following statements about the intermediates is correct?
• Consider the compound CH3-CH2-CH(X)-CH3, where X is a halogen. When treated with alcoholic KOH and heated, it undergoes elimination to give alkene products. For which choice of X will the proportion of the Hofmann (less substituted) alkene product be the greatest?

⚔️ Practice JEE Advanced Chemistry free + battle 1v1 →