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Trivial and IUPAC nomenclature: NEET MCQs with answers

89 questions on this topic of Some Basic Principles of Organic Chemistry (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. What is the IUPAC name for mesityl oxide, having the structure (CH₃)₂C=CH-CO-CH₃?

  1. Hex-3-en-2-one
  2. 2-Methylpent-2-en-4-one
  3. 4,4-Dimethylbut-3-en-2-one
  4. 4-Methylpent-3-en-2-one
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Answer: (D) 4-Methylpent-3-en-2-one

Mesityl oxide has a 5-carbon main chain containing a ketone carbonyl and an alkene double bond. The principal functional group is ketone (-one), which gets the lower locant 2. Thus, numbering from right to left gives pent-3-en-2-one with a methyl substituent at position 4, yielding 4-methylpent-3-en-2-one.

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2. What is the correct IUPAC name of the compound CH₃-N(CH₃)-CH₂-CH₂-CH₃?

  1. 1-(dimethylamino)propane
  2. N-methylpropan-2-amine
  3. N,N-dimethylpropan-1-amine
  4. N,N-dimethylpropan-2-amine
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Answer: (C) N,N-dimethylpropan-1-amine

The compound is a tertiary amine. The longest carbon chain bonded to nitrogen contains 3 carbons (propan-1-amine). The two methyl groups attached to nitrogen are designated as N,N-dimethyl. Therefore, its systematic IUPAC name is N,N-dimethylpropan-1-amine.

hard

3. Given below are two statements: Statement I: The IUPAC name of the compound CH₃-CH(OH)-C≡N is 2-hydroxypropanenitrile. Statement II: Nitriles have higher priority than alcohols in the IUPAC hierarchy of functional groups. In the light of the above statements, choose the most appropriate answer from the options given below:

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
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Answer: (A) Both Statement I and Statement II are correct

Statement II is correct because -C≡N (nitrile) has higher priority than -OH (alcohol) according to IUPAC seniority tables. Statement I is also correct because the carbon of the nitrile is C-1, making the chain three carbons long (propanenitrile) with an -OH (hydroxy) group at C-2, giving 2-hydroxypropanenitrile.

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4. Given below are two statements: Statement I: While naming acyclic hydrocarbons containing both a double and a triple bond at identical locant positions from either end, the double bond gets the lower locant. Statement II: In IUPAC nomenclature, the suffix 'yne' is written before 'en'. In the light of the above statements, choose the correct answer:

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
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Answer: (B) Statement I is correct but Statement II is incorrect

Statement I is correct: when a double bond and a triple bond are equidistant from the two ends, the double bond receives the lower number. Statement II is incorrect: the suffix 'en' is always written before 'yne' because 'e' precedes 'y' alphabetically (e.g., hept-1-en-6-yne).

easy

5. What is the correct IUPAC name of acrolein, CH₂=CH-CHO?

  1. prop-2-en-1-al
  2. prop-1-en-3-al
  3. propenol
  4. prop-2-en-1-one
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Answer: (A) prop-2-en-1-al

The principal functional group is the aldehyde (-CHO), which is assigned carbon-1. The double bond lies between carbon-2 and carbon-3. Hence, the IUPAC name is prop-2-en-1-al (or prop-2-enal).

hard

6. What is the correct IUPAC name of the polyfunctional compound O=CH-CH₂-CH(CH₃)-CO-OCH₃?

  1. 4-methoxy-2-methyl-4-oxobutanal
  2. methyl 3-methyl-4-oxobutanoate
  3. methyl 3-formylbutanoate
  4. methyl 2-methyl-4-oxobutanoate
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Answer: (D) methyl 2-methyl-4-oxobutanoate

The ester group (-COOCH₃) takes highest priority as the principal functional group. The alkyl group attached to oxygen is 'methyl'. The acyl chain is numbered starting from the ester carbonyl carbon as C-1: C-1 is -COO-, C-2 carries a methyl group (-CH₃), C-3 is -CH₂-, and C-4 is the aldehyde carbon (=O) designated as an 'oxo' substituent. Thus, the name is methyl 2-methyl-4-oxobutanoate.

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7. What is the correct IUPAC name of the compound CH₃-CH(NO₂)-CH₂-O-CH₂-CH₃?

  1. 1-Ethoxy-2-nitropropane
  2. 2-Ethoxy-1-nitropropane
  3. Ethoxy-2-nitrobutane
  4. 3-Ethoxy-2-nitropropane
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Answer: (A) 1-Ethoxy-2-nitropropane

The longest continuous carbon chain containing substituents has three carbons (propane). The functional substituents are ethoxy (-OCH₂CH₃) and nitro (-NO₂). Numbering from the end that gives lowest locants gives locants 1 for ethoxy and 2 for nitro: 1-ethoxy-2-nitropropane. Alphabetically, 'ethoxy' precedes 'nitro'.

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8. What is the correct IUPAC name of the compound CH₃-CH(CH₃)-CO-O-CH₂-CH₃?

  1. ethyl 2-methylpropanoate
  2. ethyl butanoate
  3. isopropyl ethanoate
  4. ethyl 2-methylbutanoate
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Answer: (A) ethyl 2-methylpropanoate

The given compound is an ester of the formula R-COO-R'. The alkyl group attached directly to the oxygen is an ethyl group (CH₂-CH₃). The parent acyl part contains 3 carbons in its continuous chain with a methyl group at position 2 (2-methylpropanoate). Hence, the name is ethyl 2-methylpropanoate.

easy

9. What is the correct IUPAC name of the compound CH₃-CH(OH)-CH₂-C≡CH?

  1. pent-1-yn-4-ol
  2. pent-4-yn-2-ol
  3. 4-hydroxypent-1-yne
  4. 2-hydroxypent-4-yne
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Answer: (B) pent-4-yn-2-ol

The principal functional group is alcohol (-OH), which takes precedence over the alkyne group for numbering. Numbering starts from the carbon closest to -OH, giving C2 for the -OH group and C4 for the triple bond. Hence, the correct IUPAC name is pent-4-yn-2-ol.

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10. What is the correct IUPAC name of the compound CH≡C-CH₂-CH=CH-CH₃?

  1. hex-1-yn-4-ene
  2. hex-2-en-5-yne
  3. hex-4-en-1-yne
  4. hex-5-yn-2-ene
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Answer: (C) hex-4-en-1-yne

The parent chain contains both a double bond and a triple bond. Numbering from the left gives locants 1 (yne) and 4 (ene), set (1, 4), while numbering from the right gives 2 (ene) and 5 (yne), set (2, 5). The set (1, 4) is lower than (2, 5) at the first point of difference, so numbering begins at the triple bond side. Thus, the IUPAC name is hex-4-en-1-yne.

easy

11. The trivial name 'neopentane' corresponds to which of the following IUPAC names?

  1. Pentane
  2. 2-Methylbutane
  3. 2,2-Dimethylbutane
  4. 2,2-Dimethylpropane
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Answer: (D) 2,2-Dimethylpropane

Neopentane contains a central quaternary carbon bonded to four methyl groups, C(CH₃)₄. The longest continuous carbon chain has three carbons with two methyl substituents at C2, making its IUPAC name 2,2-dimethylpropane.

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12. What is the correct IUPAC name of the compound CH₃-CO-CH₂-CH(CHO)-CH₂-COOH?

  1. 4-Formyl-2-oxohexanoic acid
  2. 3-Formyl-5-oxohexanoic acid
  3. 3-(2-Oxopropyl)pentanedioic acid
  4. 5-Oxo-3-formylhexanoic acid
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Answer: (B) 3-Formyl-5-oxohexanoic acid

Carboxylic acid (-COOH) has the highest priority and is assigned position 1. The principal chain containing 6 carbons includes the keto carbon, making the -CHO group at C3 a formyl substituent and the =O at C5 an oxo group. Alphabetically, formyl precedes oxo, giving 3-formyl-5-oxohexanoic acid.

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