Introduction: The Common system of nomenclature (up to 10 carbons) MCQs With Answer guide is designed for B. Pharm students to master IUPAC nomenclature of alkanes, alkenes, alkynes and simple substituted hydrocarbons. This concise, keyword-rich introduction emphasizes root names (meth- to dec-), chain selection, locants, substituent rules, prefixes (di-, tri-), alphabetical ordering, and functional group priorities. Practicing these systematic naming rules helps pharmacy students accurately identify structures, predict properties, and communicate chemical information in exams and research. Clear examples and targeted multiple-choice questions reinforce learning and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the IUPAC name of CH3-CH2-CH2-CH3?
- Butane
- 1-Butene
- 2-Butyne
- Isobutane
Correct Answer: Butane
Q2. What is the parent name for a straight chain of seven carbon atoms?
- Hexane
- Heptane
- Octane
- Nonane
Correct Answer: Heptane
Q3. According to IUPAC rules, how do you choose the parent chain when naming a branched alkane?
- Pick the chain with the most substituents
- Pick the chain with the maximum number of carbon atoms
- Pick the chain with the most stereocenters
- Pick the chain that gives the highest locant numbers
Correct Answer: Pick the chain with the maximum number of carbon atoms
Q4. What is the IUPAC name of CH3-CH(CH3)-CH2-CH3?
- 2-Methylbutane
- 3-Methylbutane
- Isopentane
- 2-Ethylpropane
Correct Answer: 2-Methylbutane
Q5. Which prefix denotes three identical substituents on a parent chain?
- Di-
- Tri-
- Tetra-
- Penta-
Correct Answer: Tri-
Q6. What is the IUPAC name of (CH3)2CH-CH(CH3)-CH3 (a five-carbon alkane with two methyl substituents at C2 and C3)?
- 2,3-Dimethylbutane
- 3,3-Dimethylpentane
- 2,3-Dimethylpentane
- 2,2-Dimethylbutane
Correct Answer: 2,3-Dimethylpentane
Q7. For numbering a substituted alkane, which rule is applied to give locants?
- Highest possible locants for substituents
- Lowest set of locants rule
- Alphabetical order of substituents only
- Number from the right end always
Correct Answer: Lowest set of locants rule
Q8. What is the IUPAC name of CH≡C-CH2-CH3?
- 1-Butyne
- 2-Butyne
- But-1-ene
- Butane
Correct Answer: 1-Butyne
Q9. Which root corresponds to nine carbon atoms?
- Dec-
- Non-
- Oct-
- Hept-
Correct Answer: Non-
Q10. How is numbering decided in a chain containing both double and triple bonds?
- Double bond gets the lowest possible locant; if tie, triple bond
- Triple bond always gets priority for lowest locant
- Numbering is arbitrary
- Number to give the higher priority functional group the highest number
Correct Answer: Double bond gets the lowest possible locant; if tie, triple bond
Q11. What is the IUPAC name of CH2=CH-CH2-CH3?
- 1-Butene
- 2-Butene
- Butane
- But-2-yne
Correct Answer: 1-Butene
Q12. Which substituent name corresponds to –CH2–CH3 attached to a parent chain?
- Methyl
- Ethyl
- Propyl
- Isopropyl
Correct Answer: Ethyl
Q13. What is the IUPAC name of cyclohexane with one methyl substituent?
- Methylcyclohexane
- Cyclohexylmethane
- 1-Methylcyclohexane
- Cyclohexane-methyl
Correct Answer: Methylcyclohexane
Q14. For multiple identical substituents, how are their positions indicated?
- Using commas and repeated prefixes (e.g., 2,3-dimethyl)
- By writing substituents multiple times without numbers
- By alphabetical order only
- By slash-separated locants
Correct Answer: Using commas and repeated prefixes (e.g., 2,3-dimethyl)
Q15. What is the IUPAC name of CH3-CH2-CH(CH3)-CH2-CH3?
- 3-Methylpentane
- 2-Methylpentane
- 4-Methylpentane
- 2-Ethylbutane
Correct Answer: 3-Methylpentane
Q16. Which prefix is ignored when ordering substituents alphabetically?
- sec-
- tert-
- iso-
- All of the above
Correct Answer: All of the above
Q17. What is the correct IUPAC name for (CH3)3C-CH2-CH3?
- 2-Methylbutane
- 2,2-Dimethylpropane
- 2,2-Dimethylbutane
- 3-Methylpentane
Correct Answer: 2-Methylbutane
Q18. Which of the following is the parent name for a ten-carbon straight chain?
- Decane
- Nonane
- Undecane
- Octane
Correct Answer: Decane
Q19. What is the IUPAC name of CH3-CH2-CH2-CH2-CH3?
- Pentane
- Isopentane
- Neopentane
- 2-Methylbutane
Correct Answer: Pentane
Q20. How are multiple different substituents ordered in the final name?
- By increasing locant number
- Alphabetical order of substituent names (ignoring multiplicative prefixes)
- By size of substituent
- Chronological order of discovery
Correct Answer: Alphabetical order of substituent names (ignoring multiplicative prefixes)
Q21. What is the IUPAC name of CH3-CH(CH3)-CH(CH3)-CH3?
- 2,3-Dimethylbutane
- 3,3-Dimethylbutane
- 2,2-Dimethylbutane
- 2-Ethylbutane
Correct Answer: 2,3-Dimethylbutane
Q22. Which alkane is the isomer of hexane with a methyl substituent at C3?
- 3-Methylhexane
- 3-Methylpentane
- 2-Methylhexane
- 2,3-Dimethylbutane
Correct Answer: 3-Methylhexane
Q23. What is the correct IUPAC name for CH3-CH2-CH(CH3)-CH2-CH2-CH3 (six-carbon chain with a methyl on C3)?
- 3-Methylhexane
- 2-Methylhexane
- 4-Methylhexane
- Hexane
Correct Answer: 3-Methylhexane
Q24. In the name 4-ethyl-2,3-dimethylhexane, which carbon is the parent chain based on?
- Cyclohexane
- Hexane (six-carbon straight chain)
- Heptane
- Butane
Correct Answer: Hexane (six-carbon straight chain)
Q25. What is the IUPAC name of CH3-CH2-CH2-CH(CH3)-CH3?
- 3-Methylpentane
- 2-Methylpentane
- 4-Methylpentane
- 2,3-Dimethylbutane
Correct Answer: 3-Methylpentane
Q26. Which of the following is the correct IUPAC name for the branched structure with a tert-butyl substituent on a pentane chain?
- tert-Butylpentane
- 4-(tert-Butyl)pentane
- 3-(tert-Butyl)pentane
- 2-(tert-Butyl)pentane
Correct Answer: 3-(tert-Butyl)pentane
Q27. What is the IUPAC name for CH3-CH2-C≡C-CH3?
- 2-Pentyne
- 3-Pentyne
- Pent-1-yne
- Pentane
Correct Answer: 2-Pentyne
Q28. Which of the following describes iso- prefix in common nomenclature?
- Branched chain where all carbons are in a straight line
- A methyl branch on the penultimate carbon of a chain
- A cyclized substituent only
- Indicates two identical substituents
Correct Answer: A methyl branch on the penultimate carbon of a chain
Q29. What is the IUPAC name of a six-carbon chain with a double bond at C2: CH3-CH=CH-CH2-CH2-CH3?
- Hex-2-ene
- 2-Hexene
- Hexene
- Both a and b are acceptable
Correct Answer: Both a and b are acceptable
Q30. When numbering a chain with a double bond, which end is preferred?
- The end that gives the double bond the lowest possible locant
- The end that gives the substituent highest locant
- Always from left to right
- From the end nearest a ring
Correct Answer: The end that gives the double bond the lowest possible locant
Q31. What is the IUPAC name for the structure CH3-CH(CH3)-CH2-CH2-CH3 where the longest chain is five carbons and methyl at C2?
- 2-Methylpentane
- 3-Methylpentane
- Isohexane
- 2-Ethylbutane
Correct Answer: 2-Methylpentane
Q32. Which term denotes a straight-chain alkyl substituent with three carbons?
- tert-Butyl
- n-Propyl
- Isopropyl
- sec-Propyl
Correct Answer: n-Propyl
Q33. What is the IUPAC name of the compound with formula C10H22 that is a straight chain?
- Nonane
- Decane
- Undecane
- Isodecane
Correct Answer: Decane
Q34. How do you indicate the presence of both double and triple bonds in a name?
- Use suffixes -ene and -yne with appropriate locants in alphabetical order
- Always use -yne first then -ene
- Use only -ene
- Use common names instead
Correct Answer: Use suffixes -ene and -yne with appropriate locants in alphabetical order
Q35. What is the correct IUPAC name of CH3-CH2-CH(CH3)-CH(CH3)-CH3?
- 2,3-Dimethylpentane
- 3,3-Dimethylpentane
- 2,2-Dimethylpentane
- 3-Ethylpentane
Correct Answer: 2,3-Dimethylpentane
Q36. Which of the following is true about numbering cycloalkanes with substituents?
- Numbering is not required for monosubstituted cycloalkanes
- Substituted cycloalkanes are always numbered to give substituents highest numbers
- Cycloalkanes never use locants
- Start numbering at the substituent and proceed to give substituents lowest possible numbers
Correct Answer: Start numbering at the substituent and proceed to give substituents lowest possible numbers
Q37. What is the IUPAC name for CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3?
- Nonane
- Octane
- Decane
- Heptane
Correct Answer: Nonane
Q38. In the name 3-ethyl-2-methylhexane, which substituent is listed first in the name?
- Methyl
- Ethyl
- Both listed by locant number order
- Alphabetical order dictates methyl first
Correct Answer: Ethyl
Q39. What is the IUPAC name for the branched isomer of octane having a methyl at carbon 3 of the main chain?
- 3-Methyloctane
- 3-Methyloctane is incorrect because octane has eight carbons
- 3-Methyloctane (valid for C9 compound)
- 2-Methyloctane
Correct Answer: 3-Methyloctane (valid for C9 compound)
Q40. For the molecule CH3-CH2-CH2-CH(CH3)-CH2-CH3 with the methyl on C4 of hexane, what is the IUPAC name?
- 4-Methylhexane
- 3-Methylhexane
- 2-Methylhexane
- Hexane
Correct Answer: 4-Methylhexane
Q41. Which of the following is the correct name for CH3-CH2-CH(CH2CH3)-CH3 (a butyl substituent at C3)?
- 3-Butylbutane
- 3-(Ethyl)butane
- 3-(1-Methylpropyl)butane
- 3-(Ethyl)butane is not correct naming
Correct Answer: 3-(1-Methylpropyl)butane
Q42. What is the IUPAC name of the alkane with three methyl groups on carbon 2 of pentane: (CH3)3C-CH2-CH2? (structure = 2,2,2-trimethylpropane alternative)
- 2,2,2-Trimethylbutane
- 2,2-Dimethylbutane
- Neopentane
- 2,2,3-Trimethylbutane
Correct Answer: Neopentane
Q43. When two different chains of equal length exist, how is the parent chosen?
- Choose chain with maximum number of substituents
- Choose chain alphabetically first
- Choose chain with largest substituent by mass
- Choose chain with most stereocenters
Correct Answer: Choose chain with maximum number of substituents
Q44. Which of these is the IUPAC name for CH3-CH2-CH=CH-CH2-CH3 with the double bond located between carbons 2 and 3?
- Hex-2-ene
- 3-Hexene
- Hex-3-ene
- 1-Hexene
Correct Answer: Hex-2-ene
Q45. What is the IUPAC name for 2-methylpropane commonly known as?
- Isobutane
- n-Butane
- Neohexane
- tert-Butane
Correct Answer: Isobutane
Q46. Which of the following correctly describes the locant assignment when two substituents are present at positions 2 and 4?
- List as 2,4- independent of alphabetical order
- Use 4,2- because 4 is greater
- Always list substituents alphabetically ignoring numbers
- Use Roman numerals for locants
Correct Answer: List as 2,4- independent of alphabetical order
Q47. What is the IUPAC name of the compound CH3-CH2-CH2-CH2-CH2-CH2-CH3 (seven-carbon straight chain)?
- Hexane
- Heptane
- Octane
- Nonane
Correct Answer: Heptane
Q48. Which statement is true regarding multiplicative prefixes (di-, tri-, tetra-) in alphabetical order?
- They are considered in alphabetical ordering
- They are ignored when alphabetizing substituents
- They reverse the alphabetical order
- They are used to determine locant assignment
Correct Answer: They are ignored when alphabetizing substituents
Q49. What is the IUPAC name of CH3-CH2-CH2-CH(CH2CH3)-CH3 where an ethyl group is on C4 of pentane?
- 4-Ethylpentane
- 2-Ethylpentane
- 3-Ethylpentane
- Ethylpentane (unspecified)
Correct Answer: 4-Ethylpentane
Q50. Which of the following is the correct IUPAC name for a compound with two double bonds in a six-carbon chain at C1 and C3: CH2=CH-CH=CH-CH2-CH3?
- Hexa-1,3-diene
- Hex-1,3-diene
- 1,3-Hexadiene
- Both b and c are acceptable IUPAC formats
Correct Answer: Hex-1,3-diene
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