JEE Chemistry Aldehydes Ketones And Carboxylic Acids MCQs Set 14

Answer: (d) Methyl salicylate does not occur in natural oils

Explanation:
1. Methyl salicylate (oil of wintergreen) occurs naturally in essential oils.
2. The other three statements are correct: one COOH group makes it monobasic, it is an ester, and the phenolic OH gives the violet colour while COOH gives CO2.

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: (d) Tartaric acid

Explanation:
1. Optical activity needs a chiral carbon.
2. Tartaric acid, HOOC-CH(OH)-CH(OH)-COOH, has two chiral carbons (the meso form aside).
3. Ethylene glycol, oxalic acid and glycerol have no chiral carbon.

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) C₁₅H₃₁COOH

Explanation:
1. Palmitic acid is the saturated C16 acid, so it is C₁₅H₃₁COOH.
2. C₁₇H₃₅COOH is stearic acid.

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) Benzamide (C6H5CONH2)

Explanation:
1. An amide contains the group -CONH2.
2. Only benzamide has it.

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) 3-chloropropanoic acid

Explanation:
1. The COOH carbon is C-1, so the chain is C1 (COOH), C2 (CH2), C3 (CH2Cl).
2. The name is 3-chloropropanoic acid.

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: (c) glycerides of saturated and unsaturated fatty acids

Explanation:
1. Fats and oils are triesters (glycerides) of glycerol with both saturated and unsaturated higher fatty acids.

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: (d) Soap

Explanation:
1. Soaps are sodium or potassium salts of fatty acids, not esters of glycerol.

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: (c) a secondary amide

Explanation:
1. Two acyl groups are attached to one N that also carries one H.
2. This is an imide, classed here as a secondary amide (RCONH2 is the primary amide).

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) R-C(=O)-OH, with the H on oxygen of the carboxyl group

Explanation:
1. The O-H of the carboxyl group ionises to a stabilised by delocalisation carboxylate ion.
2. R-CO-H is an aldehyde and has no acidic hydrogen.

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) Methyl salicylate

Explanation:
1. Oil of wintergreen is methyl salicylate, the methyl ester of 2-hydroxybenzoic 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: (c) both of these ways

Explanation:
1. It exists as a keto-enol tautomeric mixture.
2. The keto form gives ketone reactions and the enol form (an unsaturated hydroxy compound) gives the FeCl3 and bromine tests.

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) an acid anhydride

Explanation:
1. Two acyl groups joined through one oxygen make an acid anhydride, formed by 2RCOOH losing H2O.

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: (d) citric acid

Explanation:
1. Citric acid has three COOH groups.
2. Oxalic and tartaric acids have two, lactic acid has one.

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) soaps and detergents

Explanation:
1. Soaps and detergents have a polar head and a long non-polar hydrocarbon tail, so they are amphiphilic.

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) esters

Explanation:
1. Waxes are esters of long-chain fatty acids with long-chain alcohols.

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) an optically active acid

Explanation:
1. Glycine, H2N-CH2-COOH, is amphoteric and exists as a zwitterion.
2. It has no chiral carbon, so it is optically inactive.

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) Phenylacetic acid

Explanation:
1. Fatty acids are long straight-chain carboxylic acids.
2. Phenylacetic acid is aromatic and short.

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: (c) acetic acid

Explanation:
1. Fermentation of sugar gives ethanol, which Acetobacter oxidises to acetic acid, the acid of vinegar.

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) CnH₂n+1COOH

Explanation:
1. A saturated acid is an alkyl group CnH₂n+1 attached to COOH.
2. Equivalently the molecular formula is CnH₂nO₂, so CnH₂n+2O₂ is wrong.

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) 1

Explanation:
1. Acetamide is CH₃CONH₂, which has a single oxygen atom.

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) a monoacidic base

Explanation:
1. Urea forms salts with one equivalent of acid (for example urea nitrate), so it behaves as a monoacidic base.

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) esters

Explanation:
1. They are esters of glycerol with fatty acids.

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: (b) carboxylic acids

Explanation:
1. Saturated monocarboxylic acids and esters fit CnH₂nO₂.
2. Diketones and dialdehydes are CnH₂n-2O₂ and diols are CnH₂n+2O₂.

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) formyl chloride

Explanation:
1. Formic acid minus OH plus Cl is formyl chloride, HCOCl.

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) is a diamide of carbonic acid

Explanation:
1. Urea is H₂N-CO-NH₂, carbonic acid in which both OH groups are replaced by NH2.
2. So it is the diamide of carbonic acid.

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: (c) 1,4-benzenedicarboxylic acid

Explanation:
1. Phthalic acid is C₈H₆O₄ (benzene-1,2-dicarboxylic acid).
2. Terephthalic acid (benzene-1,4-dicarboxylic acid) has the same formula.

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: (d) none of these

Explanation:
1. Esters have the form RCOOR'.
2. All three named compounds are salts of carboxylic acids, not esters.

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) soaps

Explanation:
1. By definition soaps are the sodium or potassium salts of higher fatty acids, such as C₁₇H₃₅COONa.

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.