NEET 2025 Organic Chemistry: Alcohols & Reagents

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Questions and Answers

Assertion: Two moles of Grignard reagent is consumed in the formation of tertiary alcohol from ester followed by hydrolysis. Reason: One mole of Grignard reagent converts ester into ketone and the second mole of Grignard reagent adds to ketone.

Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion. (correct)

Assertion is correct but Reason is incorrect.

Both Assertion and Reason are incorrect.

Write the product of the following chemical reaction.

CH3CH2CH2MgBr + PhCHO ether H + --> Ph- CH-OH CH3 CH2 CH2 CH3 (correct)

S-PhMgBr + ether H + --> Ph OH

C2H5MgBr + Ph- C-CH3. ether H + --> Ph- C-CH3 OH

CH3MgBr + Ph- C-C2H5 ether H + --> Ph- C-C2H5 CH3 OH

Which of the following compound can produce chiral compound upon treatment with CH3MgCl and then acidification?

3-hexanone Et C=O --> Et CH3 C-OH npr npr

Formaldehyde H- C=O 1. CH3MgCl 2. H+ --> H CH3 C-OH

Pentanone-2 CH3 C=O --> CH3 CH3 C-OH npr npr

2-hexanone CH3 C=O --> CH3 CH3 C -OH npr npr (correct)

The reaction of Grignard reagent with formaldehyde followed by acidification gives:

A primary alcohol Signup and view all the answers

3-methyl-3-hexanol cannot be prepared by

C3H7MgI and 2-butanone followed by hydrolysis Signup and view all the answers

When CH3MgI is made to react with acetone and the addition product is hydrolysed, we get:

tertiary alcohol Signup and view all the answers

Phenyl magnesium bromide reacts with methanol to give:

a mixture of benzene and Mg(OMe)Br Signup and view all the answers

Ethyl acetate reacts with CH3MgBr to form

tertiary alcohol Signup and view all the answers

Reaction of esters with Grignard reagents give rise to:

ketones Signup and view all the answers

Which of the following compound does not react with methyl magnesium bromide to produce tertiary alcohol?

Ethyl benzoate Signup and view all the answers

Et-O-C=O-Et 1. CH3MgBr 2. H3O+ (A), Product (A) is:

CH3-C-CH3 OH CH3 Signup and view all the answers

In which of the following reaction 2º alcohol is obtained as a product?

Both (A) and (B) Signup and view all the answers

All of the following compound react with ethyl magnesium bromide. Alcohols are formed from three of the compounds. Which one does not give as alcohol?

Ph-O-C=O-H Signup and view all the answers

Acetone on reaction with methyl magnesium bromide followed by hydrolysis gives.

Tertiary alcohol Signup and view all the answers

Which of the following are the starting materials for the Grignard's synthesis of tert. butyl alcohol?

CH3MgI + CH3COCH3 Signup and view all the answers

Isobutyl alcohol can be obtained by the reaction between:

(CH3)2CHMgBr and HCHO Signup and view all the answers

In the following sequence of reactins, CH3CH2OH -> P+12 -> (a) -> Mg -> (B) -> HCHO -> (C) -> H2O -> (D) ether the compound D is:

n-propyl alcohol Signup and view all the answers

P -> PhMgBr -> H2O -> CH3-CH-Ph (d+l)
P can be:

CH3CHO Signup and view all the answers

Formaldehyde forms an addition product with CH3MgI which on hydrolysis gives:

ethyl alcohol Signup and view all the answers

CH3-CH2-C-CH3 (i) CH2MgBr (ii) H2O Product is:

CH3-CH2-C-CH3 CH3 OH Signup and view all the answers

From which of the following tertiary butyl alcohol is obtained by the action of methyl magnesium iodide?

CH3COCH3 Signup and view all the answers

H + CH3MgBr --> A --> H3O+ --> B

3-methylbutan-2-ol Signup and view all the answers

Study Notes

Organic Chemistry Lecture Notes

Course: NEET 2025
Topic: Alcohols, Phenols and Ethers
Lecturer: Pankaj Sir (POPU MAMA)
Topics Covered:
- Methods of Preparation of Alcohols (Part 3)
- Grignard Reagent
- Practice Problems

Methods of Preparation of Alcohols (Part 3) - Grignard Reagent

Grignard reagents (R-MgX) react with various compounds, including acid derivatives (e.g., aldehydes, ketones, esters).
The reaction proceeds in multiple steps:
- Addition to Carbonyl Compounds: The Grignard reagent acts as a nucleophile, attacking the carbonyl carbon. This forms a new carbon-carbon bond.
- Hydrolysis: The addition product is subsequently hydrolyzed (treated with water), leading to the formation of an alcohol.
- Acid Derivatives: These are compounds that contain functional groups (e.g., carboxylic acid groups).
- Nucleophilic Addition: Grignard reagents add to the carbonyl group of acid derivatives.
- Elimination: The reaction proceeds through acid derivatives and elimination steps.
Steric factors and electronic factors influence the reaction rate.
Bulkier groups can hinder the approach of the nucleophile, thus decrease the reaction rate.

Mechanism of NAR (Nucleophilic Addition Reaction)

Nucleophilic addition reaction mechanisms in carbonyl compounds.
Nucleophilic attacks carbonyl carbon to form a tetrahedral intermediate.
The intermediate loses a leaving group to regenerate the carbonyl group.
Steps in the NAR mechanism: Addition, Proton transfer, and loss of the leaving group.

Reaction of Grignard Reagents with Cyclic Ethers

Limited reactivity: Only certain cyclic ethers (e.g., 3- and 4-membered rings) undergo reactions with Grignard reagents.
Stability and sterics play a role in determining reactivity

Reactions and Product Formation

Various reactions and their products (using different reagents).

Mechanism of SN2 Reaction in Acid Derivatives

SN2 reaction in acid derivatives is shown.

Reaction of Ester-Grignard Reagents

Esters react with Grignard reagents to produce tertiary alcohols.
The reaction involves nucleophilic attack on the carbonyl group by the Grignard reagent.
Hydrolysis step forms a tertiary alcohol as a final product.

Alcohol Production from Reactions

Various chemical reactions that yield tertiary alcohol(s).

Additional Information

Question on tertiary alcohol synthesis from carbonyl compounds.
The role of specific Grignard reagents (e.g., CH3MgBr) in producing various alcohols.
Determining the correct starting materials to form a specific tertiary alcohol using Grignard reactions.
Other Reactions for producing Tertiary Alcohols
Identifying the compound that does not form an alcohol when treated with ethyl magnesium bromide.

Answer Key

Correct answers to the questions are provided.

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Description

Prepare for the NEET 2025 exam with this focus on Alcohols, Phenols, and Ethers, specifically covering Methods of Preparation of Alcohols and Grignard Reagents. Dive into practice problems and enhance your understanding of nucleophilic addition and hydrolysis. Ideal for students aiming to excel in Organic Chemistry.