Question

Correct statement(s) about Q and R is/are

• A. Both Q and R give positive Fehling’s test
• B. Q gives positive iodoform test and its ¹H NMR spectrum shows singlets at 1.0 ppm (3H) and at 1.3 ppm (3H)
• C. R gives positive iodoform test and its¹H NMR spectrum shows singlets at 1.0 ppm (3H) and at 2.2 ppm (3H)
• D. A bright yellow precipitate is formed when Q and R treated separately with 2,4 dinitrophenyl hydrazine

Answer 1

The Correct Option is C, D

To determine which statements about Q and R are correct, let's analyze each reaction and the tests involved.

1. Fehling’s Test: This test is used to identify reducing sugars and aldehydes, but Q and R are not clearly aldehydes, so neither gives a positive Fehling’s test.
2. Iodoform Test for R:
   • The iodoform test identifies compounds with the structure CH₃CO- or CH₃CHOH- groups. R can undergo this test showing it contains such groups.
   • R gives a positive iodoform test, confirming the presence of a methyl ketone or secondary alcohol with a methyl group.
   • The ¹H NMR spectrum of R shows singlets at 1.0 ppm (3H) and 2.2 ppm (3H), aligning with typical chemical shifts for a methyl group and a methyl ketone.
3. 2,4-Dinitrophenylhydrazine (DNPH) Test for Q and R:
   • DNPH reacts with carbonyl groups to form a yellow precipitate, which indicates the presence of an aldehyde or ketone.
   • Both Q and R likely contain carbonyl groups, given that they form bright yellow precipitates when treated with DNPH.

Based on this analysis, the correct statements are:

• R gives a positive iodoform test and its¹H NMR spectrum shows singlets at 1.0 ppm (3H) and at 2.2 ppm (3H).
• A bright yellow precipitate is formed when Q and R are treated separately with 2,4-dinitrophenylhydrazine.