Write the name of the reaction, structure and IUPAC name of the product formed when (any 2): (a) phenol reacts with CHCl_3 in the presence of NaOH followed by hydrolysis. (b) CH_3CH_2CH(CH_3)CH(CH_3)ONa reacts with C_2H_5Br (c) CH_3CH_2CN reacts with stannous chloride in the presence of hydrochloric acid followed by hydrolysis

ChemistryCBSE Class 12 · Sample paper, session 2023-24 · 3 marks · Short answer

CBSE Class 12 Chemistry sample paper 2023-24: question 24

From the official CBSE sample question paper for 2023-24, section C, question 24, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q24 · 3 marks · Short answerAlcohols, Phenols and Ethers

Write the name of the reaction, structure and IUPAC name of the product formed when (any 2):

(a)
phenol reacts with $CHC l_{3}$ in the presence of NaOH followed by hydrolysis.
0 marks
(b)
$C H_{3} C H_{2} CH (C H_{3}) CH (C H_{3}) ONa$ reacts with $C_{2} H_{5} Br$
0 marks
(c)
$C H_{3} C H_{2} CN$ reacts with stannous chloride in the presence of hydrochloric acid followed by hydrolysis
0 marks

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.

Hints

Open one hint at a time and try again before the next.

Hint 1

Ask which named reaction each set of reagents belongs to.

Hint 2

(a) gives an aldehyde group ortho to –OH; (b) is an alkoxide reacting with an alkyl halide.

Hint 3

(c): SnCl₂/HCl reduces a nitrile to an imine, which hydrolyses to an aldehyde.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

(a) Reimer–Tiemann reaction. Phenol with CHCl₃/NaOH gives a –CHCl₂ intermediate at the ortho position, which is hydrolysed to salicylaldehyde, $o - HO C_{6} H_{4} CHO$ . IUPAC name: 2-hydroxybenzaldehyde.
1½ marks
(b) Williamson ether synthesis: $C H_{3} C H_{2} CH (C H_{3}) CH (C H_{3}) ONa + C_{2} H_{5} Br \to C H_{3} C H_{2} CH (C H_{3}) CH (C H_{3}) O C_{2} H_{5} + NaBr$ . IUPAC name: 2-ethoxy-3-methylpentane.
1½ marks
(c) Stephen reaction (alternative part, 1.5 marks if chosen): $C H_{3} C H_{2} CN SnC l_{2} /HCl C H_{3} C H_{2} CH = NH H_{3} O^{+} C H_{3} C H_{2} CHO$ . IUPAC name: propanal.

Answer: (a) Reimer–Tiemann, 2-hydroxybenzaldehyde; (b) Williamson synthesis, CH₃CH₂CH(CH₃)CH(CH₃)OC₂H₅, 2-ethoxy-3-methylpentane; (c) Stephen reaction, CH₃CH₂CHO, propanal

Where the marks are

Each chosen part: name of reaction (½ mark)
Each chosen part: correct structure of product (½ mark)
Each chosen part: correct IUPAC name (½ mark); any two parts total 3 marks

Revise the chapter

Chapter: Alcohols, Phenols and Ethers (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Alcohols, Phenols and Ethers, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2023-24: every question, by section.

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CBSE Class 12 Chemistry sample paper 2023-24: question 24

Hints

Step-by-step solution

Revise the chapter

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