IUPAC Nomenclature - JEE Main Previous Year Questions with Solutions

The IUPAC name of neopentane is 2,2-dimethylpropane. Neopentane has a central carbon bonded to four methyl groups (C(CH₃)₄). The longest chain is 3 carbons (propane) and two methyl groups are at C-2, giving 2,2-dimethylpropane. This was directly asked in AIEEE 2009.

Typically 1 question per session appears from IUPAC nomenclature in JEE Main. Since JEE Main now runs in multiple sessions per year, you can expect 1–2 questions annually from this topic. It is consistently Easy to Medium in difficulty and a reliable source of marks.

1,2-Epoxypropane is the IUPAC name for propylene oxide — a three-membered ring with one oxygen atom bridging C-1 and C-2 of propane. Its systematic name uses the "epoxy" prefix on the parent alkane chain. This compound was tested in AIEEE 2012 (Online).

Carboxylic acids (–COOH) hold the highest priority in IUPAC nomenclature and are always expressed as the principal characteristic group (suffix: -oic acid). The general priority order is: –COOH > –CHO > –OH (alcohol) > –C=O (ketone) > –NH₂ > C=C > C≡C.

n-Butane's IUPAC name is simply butane (4 carbons in a straight chain). Isobutane's IUPAC name is 2-methylpropane (3-carbon chain with one methyl branch at C-2). Both have the same molecular formula C₄H₁₀ but different structural arrangements (structural isomers).