Question

The IUPAC name of the compound CH3−CH2−CH=CH2 is

• A. but-1-ene
• B. but-3-ene
• C. but-2-ene

Answer 1

The correct option is A but-1-ene

The carbon chain has four carbon atoms in the parent chain. So, the word root is 'but'.
The chain should be numbered in such a way that the carbon atom containing the double bond gets the lowest number a shown below.

${\mathrm{CH}}_2={\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_{3}1234$

Hence the IUPAC name of the compound is 'but-1-ene'.