JEE Chemistry Aldehydes Ketones And Carboxylic Acids MCQs Set 19

Answer: (c) CH₃CH₂CCl₂COOH

Explanation:
1. Two Cl atoms on the alpha carbon give the largest -I effect and the most stable anion.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (a) saponification

Explanation:
1. It gives the carboxylate salt and alcohol, as in making soap from fats.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (c) acetonitrile

Explanation:
1. A = CH₃COONH₄, which with P₂O₅ is dehydrated (via acetamide) to acetonitrile, CH₃CN.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (b) alcohol with LiAlH₄

Explanation:
1. LiAlH₄ reduces RCOOH to RCH₂OH.
2. HI and red P give the alkane.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (c) acetamide

Explanation:
1. CH₃CONH₂ + NaOH → CH₃COONa + NH₃.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (b) BrCH₂-(CH₂)₆COOH

Explanation:
1. Peroxide reverses the addition of HBr, so Br adds to the terminal carbon (anti-Markovnikov).

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (a) it has one aldehyde group

Explanation:
1. HCOOH can be written H-C(=O)-OH, so it carries an aldehyde-type group.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (c) RCOOH > HOH > ROH > HC≡CH

Explanation:
1. Approximate pKa values: carboxylic acid about 5, water 15.7, alcohol about 16-18, ethyne 25.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (a) anhydrides, esters, ethers

Explanation:
1. Anhydrides are the most reactive acyl compounds, esters less, and ethers do not react with ammonia.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (a) 1,1-diphenylethanol

Explanation:
1. The Grignard reagent adds twice to give a tertiary alcohol, CH₃C(OH)(C₆H₅)₂.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (b) chloroacetic acid

Explanation:
1. Cl has a -I effect that is stronger than the effect of H in formic acid.
2. Chloroacetic acid pKa is about 2.9 and formic acid is 3.77.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (b) NH₂CONHCONH₂

Explanation:
1. Heating urea gives biuret and ammonia.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (c) CH₂BrCH₂(CH₂)₈COOH

Explanation:
1. In the presence of peroxide, HBr adds anti-Markovnikov, putting Br on the terminal carbon.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (b) salicylic acid

Explanation:
1. Aspirin is O-acetylsalicylic acid.
2. Salicylic acid's OH is acetylated by acetic anhydride.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (a) an acid

Explanation:
1. RCOOH + PCl₅ → RCOCl + POCl₃ + HCl.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (d) aniline > cyclohexylamine > benzamide (basic strength)

Explanation:
1. Cyclohexylamine is a stronger base than aniline because the lone pair of aniline is delocalised into the ring.
2. So the order in (d) is wrong.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (c) CH₃COOH

Explanation:
1. Ethanol and acetic acid give ethyl acetate, which smells fruity.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (a) FCH₂COOH > ClCH₂COOH > BrCH₂COOH

Explanation:
1. The -I effect follows electronegativity: F > Cl > Br.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (c) CH₃NH₂

Explanation:
1. Hofmann bromamide degradation removes the carbonyl carbon: CH₃CONH₂ → CH₃NH₂.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (d) formic acid

Explanation:
1. Formic acid is the only simple monocarboxylic acid with an aldehyde-type H, so it reduces Tollens' and Fehling's reagents.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (a) ammoniacal silver nitrate solution

Explanation:
1. Only methanoic acid gives a silver mirror.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (a) methyl formate

Explanation:
1. A is formic acid, which reduces Fehling's solution.
2. B must be methanol, since methanol oxidises to formic acid.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.

Answer: (b) RCOX > RCOOCOR > RCOOR > RCONH₂

Explanation:
1. The better the leaving group, the more reactive: Cl- > RCOO- > RO- > NH2-.

Teacher's Note:
1. Always link acid strength to the stability of the carboxylate ion.
2. Electron-withdrawing groups increase acidity and electron-donating groups decrease it.

Answer: (b) CH₂ClCOOH > HCOOH > CH₃COOH > C₂H₅COOH

Explanation:
1. Cl withdraws electrons and raises acidity most.
2. Alkyl groups donate electrons, and the larger ethyl group lowers acidity more than methyl.

Teacher's Note:
1. Note the name reaction and write its equation once in your notebook.
2. Such one-step recall questions are common in the JEE and NEET style papers.

Answer: (b) sodium benzoate and ethanol

Explanation:
1. C₆H₅COOC₂H₅ + NaOH → C₆H₅COONa + C₂H₅OH.

Teacher's Note:
1. Count carbons before and after the reaction to avoid mistakes in chain-length changes.
2. Check whether the reagent is a reducing, oxidising or dehydrating agent before choosing the product.

Answer: (b) pyruvic acid

Explanation:
1. The secondary alcohol group of CH₃CH(OH)COOH is oxidised to a keto group, giving pyruvic acid.

Teacher's Note:
1. Eliminate options by checking functional groups on both sides of the reaction.
2. Only one option will have the correct functional group and carbon skeleton.

Answer: (d) LiAlH₄

Explanation:
1. Strong hydride donors such as LiAlH₄ reduce carboxylic acids to primary alcohols.

Teacher's Note:
1. Revise the physical properties such as hydrogen bonding and boiling points together with the chemistry.
2. Compare similar compounds in pairs when you are asked to rank them.

Answer: (d) CH₃COOH

Explanation:
1. Neutral ferric chloride gives a red colour with acetic acid because iron(III) acetate complex forms.

Teacher's Note:
1. Learn the reactivity order of acid derivatives: acyl chloride, anhydride, ester, amide.
2. Most questions of this type are solved by recalling the standard reagent and product pair.