What is the IUPAC name of the compound CH3–CH(Cl)–CH(CH3)–CH(CH3)–CH2OH?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 4-Chloro-2,3-dimethylpentan-1-ol
Compound: \( \ce{CH3-CH(Cl)-CH(CH3)-CH(CH3)-CH2OH} \)
Parent chain: the longest chain holding the carbon with –OH has five carbons: pentanol.
Numbering: start at the end nearest the –OH group, so \( \ce{CH2OH} \) is C-1: pentan-1-ol.
Substituents: \( \ce{CH3} \) groups on C-2 and C-3 (2,3-dimethyl) and Cl on C-4 (4-chloro).
Order of prefixes: prefixes are written in alphabetical order, and “di” is not counted, so chloro (c) comes before methyl (m).
Name: 4-chloro-2,3-dimethylpentan-1-ol. Numbering from the other end (2-chloro-3,4-dimethyl) would give the –OH carbon the number 5, and writing dimethyl first breaks the alphabetical order.
NCERT (2026-27 edition):
7.2 Nomenclature – “… The position of substituents are indicated by numerals. For this, the longest carbon chain (parent chain) is numbered starting at the end nearest to the hydroxyl group. The positions of the –OH group and other substituents are indicated by using the numbers of carbon atoms to which these are attached.”