IUPAC system of nomenclature (up to 10 carbons) MCQs With Answer

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IUPAC system of nomenclature (up to 10 carbons) MCQs With Answer

The IUPAC system of nomenclature is essential for B. Pharm students to accurately name organic molecules, especially alkanes, alkenes and alkynes up to 10 carbons. This concise, systematic approach covers selecting the parent chain, assigning locants, using prefixes and suffixes, ordering substituents, and naming branched isomers. Mastery of terms like parent chain, substituent, locant, multiplicative prefixes (di, tri), and preferred IUPAC names (propan-2-yl, but-2-yl) improves communication in medicinal chemistry, drug design and pharmacognosy. These MCQs focus on practical naming rules, common pitfalls and isomer identification to build strong organic nomenclature skills. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the correct IUPAC name for CH3CH2CH2CH3?

  • Methane
  • Propane
  • Butane
  • Pentane

Correct Answer: Butane

Q2. The IUPAC suffix for a saturated hydrocarbon (no multiple bonds) is:

  • -ene
  • -yne
  • -ane
  • -ol

Correct Answer: -ane

Q3. Which parent name corresponds to a seven-carbon straight chain?

  • Hexane
  • Heptane
  • Octane
  • Nonane

Correct Answer: Heptane

Q4. According to IUPAC, when numbering a chain with an alkene, numbering should start from the end nearest to the:

  • Longest substituent
  • End with more hydrogen atoms
  • Double bond
  • First methyl group

Correct Answer: Double bond

Q5. The preferred IUPAC name for the substituent (CH3)2CH- is:

  • isopropyl
  • propan-2-yl
  • 1-methylethyl
  • sec-propyl

Correct Answer: propan-2-yl

Q6. How many structural isomers exist for C4H10?

  • 1
  • 2
  • 3
  • 4

Correct Answer: 2

Q7. Choose the correct IUPAC name for CH3CH(CH3)CH2CH3:

  • 2-methylbutane
  • 3-methylbutane
  • butan-2-yl
  • 2-ethylpropane

Correct Answer: 2-methylbutane

Q8. When two substituents are present, the locants should give:

  • The highest possible numbers
  • Lowest set of locants at the first point of difference
  • Numbers in descending order
  • Alphabetical order of numbers

Correct Answer: Lowest set of locants at the first point of difference

Q9. The multiplicative prefix for three identical substituents is:

  • di
  • tri
  • tetra
  • mono

Correct Answer: tri

Q10. Which of the following is the correct IUPAC name for the isomer commonly called isobutane?

  • 2-methylpropane
  • 1-methylpropane
  • butan-2-yl
  • propan-1-yl

Correct Answer: 2-methylpropane

Q11. For alphabetizing substituents in the name, which prefixes are ignored?

  • di, tri, tetra
  • iso, neo, cyclo
  • sec, tert, iso
  • all prefixes are considered

Correct Answer: di, tri, tetra

Q12. What is the correct IUPAC name for CH3CH2CH(CH3)CH2CH3?

  • 3-methylpentane
  • 2-methylpentane
  • 4-methylpentane
  • pentan-3-yl

Correct Answer: 3-methylpentane

Q13. Which parent name corresponds to a ten-carbon straight chain?

  • Nonane
  • Decane
  • Undecane
  • Heptane

Correct Answer: Decane

Q14. The correct name for CH3-CH2-CH=CH-CH3 with the double bond starting at carbon 2 is:

  • pent-2-ene
  • 2-pentene
  • pentene-2
  • both a and b are acceptable, but IUPAC prefers pent-2-ene

Correct Answer: both a and b are acceptable, but IUPAC prefers pent-2-ene

Q15. When choosing the parent chain, if two chains have equal length, priority is given to the chain with:

  • More substituents overall
  • More multiple bonds (double/triple)
  • Fewer substituents
  • More carbonyl groups only

Correct Answer: More multiple bonds (double/triple)

Q16. Which is the IUPAC name for CH3CH2C≡CH?

  • 1-butyne
  • but-1-yne
  • but-2-yne
  • 2-butyne

Correct Answer: but-1-yne

Q17. The substituent -CH2CH2CH3 is called:

  • ethyl
  • propyl
  • butyl
  • methylpropyl

Correct Answer: propyl

Q18. Which of the following is the correct IUPAC name for 2,2-dimethylpropane?

  • neopentane
  • 2,2-dimethylpropane is incorrect; it should be 2-methylbutane
  • 2,2-dimethylpropane
  • tert-pentane

Correct Answer: 2,2-dimethylpropane

Q19. For cycloalkanes with one substituent, the substituent carbon is numbered as:

  • 1
  • 2
  • Depends on substituent name
  • No numbering is used

Correct Answer: 1

Q20. How many structural isomers exist for C5H12?

  • 2
  • 3
  • 4
  • 5

Correct Answer: 3

Q21. The correct IUPAC name for CH3CH2CH2CH2CH3 is:

  • pentane
  • 2-pentane
  • pent-1-ane
  • butane

Correct Answer: pentane

Q22. When naming a compound with substituents including “ethyl” and “methyl”, which is placed first alphabetically?

  • methyl
  • ethyl
  • alphabetical order is not used
  • order depends on size of substituent

Correct Answer: ethyl

Q23. The IUPAC name for CH3CH(CH3)2 (a three-carbon chain with methyl on carbon 2) is:

  • isopropane
  • propan-2-yl
  • propane
  • 2-methylpropane

Correct Answer: 2-methylpropane

Q24. In a chain containing both double and triple bonds, how is the parent chain chosen?

  • Longest chain irrespective of multiple bonds
  • Chain with maximum number of multiple bonds
  • Chain with more methyl groups
  • Shortest chain with functional groups

Correct Answer: Chain with maximum number of multiple bonds

Q25. The correct IUPAC name for CH3CH2C(CH3)2CH3 is:

  • 2,3-dimethylbutane
  • 3-methylpentane
  • 3,3-dimethylbutane
  • 2,2-dimethylpentane

Correct Answer: 3-methylpentane

Q26. Which of the following is the parent name for a six-carbon straight chain?

  • Pentane
  • Hexane
  • Heptane
  • Octane

Correct Answer: Hexane

Q27. The IUPAC name but-2-ene indicates the double bond is between which carbons?

  • C1 and C2
  • C2 and C3
  • C3 and C4
  • Between any two carbons

Correct Answer: C2 and C3

Q28. Which statement about numbering to give lowest set of locants is true?

  • Always number from left to right
  • Choose the direction that gives the smallest first locant at the first point of difference
  • Choose direction that gives highest second locant
  • Numbering direction is random

Correct Answer: Choose the direction that gives the smallest first locant at the first point of difference

Q29. The IUPAC preferred name for the substituent -CH2CH(CH3)2 is:

  • isobutyl
  • 2-methylpropyl
  • 1-methylpropyl
  • sec-butyl

Correct Answer: 2-methylpropyl

Q30. What is the IUPAC name for CH3CH2CH(CH3)CH2CH2CH3?

  • 3-methylhexane
  • 2-methylhexane
  • 4-methylhexane
  • hexan-3-yl

Correct Answer: 3-methylhexane

Q31. When identical substituents are present, locants should be:

  • In descending order
  • Combined using commas and indicated by multiplicative prefix
  • Listed separately without commas
  • Shown as ranges

Correct Answer: Combined using commas and indicated by multiplicative prefix

Q32. The IUPAC name for CH3CH2CH2CH2CH2CH3 is:

  • hexane
  • heptane
  • pentane
  • butane

Correct Answer: hexane

Q33. How should substituents be separated from numbers in the IUPAC name?

  • By spaces only
  • By hyphens
  • By commas only
  • No separators are used

Correct Answer: By hyphens

Q34. Which of the following is the correct IUPAC name for CH3C(CH3)2CH2CH3?

  • 3-methylpentane
  • 2,2-dimethylbutane
  • 2-methylpentane
  • 3,3-dimethylbutane

Correct Answer: 3-methylpentane

Q35. For the molecule CH3CH=CHCH2CH3, the correct IUPAC name is:

  • pent-1-ene
  • pent-2-ene
  • 2-pentene
  • 1-pentene

Correct Answer: pent-2-ene

Q36. Which is the IUPAC name for a three-carbon chain parent?

  • ethane
  • propane
  • butane
  • methane

Correct Answer: propane

Q37. In naming 2,3-dimethylbutane, what are the locants of methyl groups?

  • 1 and 4
  • 2 and 3
  • 1 and 3
  • 2 and 4

Correct Answer: 2 and 3

Q38. The IUPAC name for a nine-carbon straight chain is:

  • nonane
  • decane
  • octane
  • enneane

Correct Answer: nonane

Q39. When a substituent is complex (contains substituents itself), it is named as a:

  • prefix only
  • parenthetical group using parentheses
  • separate molecule
  • omitted from name

Correct Answer: parenthetical group using parentheses

Q40. The correct IUPAC name for CH3CH2CH2CH(CH3)2 is:

  • 4-methylhexane
  • 3-methylpentane
  • 3,3-dimethylbutane
  • 2-methylpentane

Correct Answer: 3-methylpentane

Q41. Which rule applies when numbering a chain with both substituents and a functional group (higher priority absent here)?

  • Give substituents highest numbers
  • Number to give lowest locants to substituents and multiple bonds following priority rules
  • Always start at the leftmost carbon in the formula
  • Number to maximize sum of locants

Correct Answer: Number to give lowest locants to substituents and multiple bonds following priority rules

Q42. The IUPAC name for CH3CH2C(CH3)3 is:

  • 2,2-dimethylbutane
  • tert-butylpropane
  • 3-methylpentane
  • 2,2-dimethylpropane

Correct Answer: 2,2-dimethylbutane

Q43. Which of the following is the correct IUPAC name for CH3CH2CH=CH2?

  • but-1-ene
  • but-2-ene
  • 1-butene
  • 2-butene

Correct Answer: but-1-ene

Q44. For naming branched alkanes, the longest continuous chain must include:

  • Maximum number of substituents only
  • Maximum number of carbon atoms
  • Maximum hydrogen atoms
  • Maximum number of identical substituents

Correct Answer: Maximum number of carbon atoms

Q45. The substituent name “sec-butyl” in preferred IUPAC terminology is usually replaced by:

  • butan-2-yl
  • butyl
  • 2-bromobutyl
  • isobutyl

Correct Answer: butan-2-yl

Q46. The IUPAC name for CH3-CH(CH3)-CH2-CH2-CH3 is:

  • 2-methylpentane
  • 3-methylpentane
  • 2-ethylbutane
  • pentan-2-yl

Correct Answer: 2-methylpentane

Q47. For the compound with formula C6H14 that is 2-methylpentane, the total number of carbon atoms in the parent chain is:

  • 4
  • 5
  • 6
  • 3

Correct Answer: 5

Q48. Which of the following demonstrates correct use of multiplicative prefix and locants?

  • 2,2,3-trimethylhexane
  • 2,2,3 trimethyl hexane
  • 2,2,3-trimethyl-hexane
  • 224-trimethylhexane

Correct Answer: 2,2,3-trimethylhexane

Q49. The IUPAC name for the linear four-carbon substituent -CH2CH2CH2CH3 is:

  • butyl
  • sec-butyl
  • isobutyl
  • tert-butyl

Correct Answer: butyl

Q50. Which guideline is correct when naming an alkane with several different substituents?

  • List substituents alphabetically, ignore multiplicative prefixes for alphabetizing
  • Order substituents by size instead of alphabet
  • Include multiplicative prefixes in alphabetizing
  • Always list substituents by increasing locant value only

Correct Answer: List substituents alphabetically, ignore multiplicative prefixes for alphabetizing

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