Question

Write structures of the following compounds: (i) 2-Chloro-3-methylpentane
(ii) 1,4-dibromobut-2-ene
(iii) 1-Bromo-2,2-dimethylpropane
(iv) 1-Bromo-2-methylbut-2-ene
(v) 1-Chloro-2-methylbenzene

Hint:

When writing structures from IUPAC names: (1) pick the parent chain/ring, (2) place the multiple bond(s) at the specified locant(s), (3) add substituents at their locants, and (4) check valency at each carbon.

Answer 1

(i) 2-Chloro-3-methylpentane
Condensed structure: \(\mathrm{CH_3{-}CH(Cl){-}CH(CH_3){-}CH_2{-}CH_3}\)
Main chain = pentane; Cl at C-2; methyl at C-3.
(ii) 1,4-Dibromobut-2-ene
Condensed structure: \(\mathrm{Br{-}CH_2{-}CH{=}CH{-}CH_2{-}Br}\)
But-2-ene backbone (\(C_2{=}C_3\)); Br at C-1 and C-4.
(iii) 1-Bromo-2,2-dimethylpropane (neopentyl bromide)
Condensed structure: \(\mathrm{(CH_3)_3C{-}CH_2{-}Br}\)
Choose the propane chain \(\mathrm{CH_3{-}C(CH_3)_2{-}CH_2Br}\); Br at C-1; two \(\mathrm{CH_3}\) groups at C-2.
(iv) 1-Bromo-2-methylbut-2-ene
Condensed structure: \(\mathrm{Br{-}CH_2{-}C(CH_3){=}CH{-}CH_3}\)
But-2-ene backbone (\(C_2{=}C_3\)); Br at C-1; methyl substituent at C-2.
(v) 1-Chloro-2-methylbenzene (o-chlorotoluene)
Aromatic structure: benzene ring with adjacent substituents \(\mathrm{Cl}\) at C-1 and \(\mathrm{CH_3}\) at C-2.
Condensed/SMILES: \(\mathrm{Clc_1cccc(c_1)CH_3}\).