Step-by-Step Guidance for Organic Chemistry Reactions: Carboxylic Acid Derivatives, Condensations & Alpha Carbon Reactions

Q1. Predict the product for the following sequence: ethyl cyanide reacts with (1) OH/H2O, (2) acetyl chloride, (3) phthalic acid/AlCl3.

Background

Topic: Carboxylic Acid Derivatives & Friedel-Crafts Acylation

This question tests your understanding of multi-step organic synthesis, including hydrolysis of nitriles, acylation reactions, and aromatic substitution.

Key Terms and Formulas

• Nitrile hydrolysis: Conversion of a nitrile to a carboxylic acid using aqueous base.

• Acyl chloride: Used for acylation reactions, often in Friedel-Crafts reactions.

• Friedel-Crafts acylation: Aromatic substitution using AlCl3 as a catalyst.

Step-by-Step Guidance

1. $\text{Step 1: Hydrolyze the nitrile group (–CN) to a carboxylic acid using OH/H_2O.}$

2. $\text{Step 2: React the resulting carboxylic acid with acetyl chloride to form an anhydride or acyl derivative.}$

3. $\text{Step 3: Use phthalic acid and AlCl_3 to perform a Friedel-Crafts acylation on an aromatic ring.}$

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Q2. Predict the product for the following sequence: cyclopentane-1,3-dione reacts with (1) NaOEt/EtOH, (2) ethyl bromide, (3) H2O/180°C.

Background

Topic: Alpha Carbon Reactions & Alkylation

This question tests your ability to perform enolate formation, alkylation, and subsequent hydrolysis/decarboxylation.

Key Terms and Formulas

• Enolate formation: Deprotonation of an alpha hydrogen using a base.

• Alkylation: Reaction of an enolate with an alkyl halide.

• Decarboxylation: Loss of CO2 from a carboxylic acid under heat.

Step-by-Step Guidance

1. $\text{Step 1: Use NaOEt/EtOH to generate the enolate from cyclopentane-1,3-dione.}$

2. $\text{Step 2: Alkylate the enolate with ethyl bromide to introduce an ethyl group at the alpha position.}$

3. $\text{Step 3: Hydrolyze and heat to induce decarboxylation, removing a carboxyl group.}$

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Q3. Predict the product for the following sequence: benzamide reacts with (1) POCl3, (2) CH3MgBr then H2O, (3) NaOEt/EtOH/Heat.

Background

Topic: Carbonyl Condensations & Alpha Carbon Reactions

This question tests your understanding of amide dehydration, Grignard addition, and enolate chemistry.

Key Terms and Formulas

• Amide dehydration: Conversion of an amide to a nitrile using POCl3.

• Grignard addition: Nucleophilic addition of a Grignard reagent to a nitrile.

• Enolate formation and condensation: Use of base to form enolate and subsequent condensation.

Step-by-Step Guidance

1. $\text{Step 1: Dehydrate benzamide to benzonitrile using POCl_3.}$

2. $\text{Step 2: Add CH_3MgBr to the nitrile, followed by hydrolysis, to form a ketone.}$

3. $\text{Step 3: Use NaOEt/EtOH and heat to form an enolate and perform condensation.}$

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Q4. Predict the product for the following sequence: glutaric acid reacts with (1) NaBH4/EtOH, (2) H+

Background

Topic: Reduction of Carboxylic Acids

This question tests your understanding of reduction reactions, specifically the use of NaBH4 to reduce carboxylic acids or esters.

Key Terms and Formulas

• NaBH4: Sodium borohydride, a reducing agent.

• Reduction: Conversion of carboxylic acids to alcohols.

Step-by-Step Guidance

1. $\text{Step 1: Use NaBH_4/EtOH to reduce the carboxylic acid groups.}$

2. $\text{Step 2: Acid workup (H^+) to protonate the product and complete the reduction.}$

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