Unsaturated hydrocarbons

3 marks · Easy

(a)

Draw the displayed formula of a straight-chain isomer of butene where the double bond is between the second and third carbon atoms.

[2 marks]

(b)

Name this isomer.

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) Displayed formula for CH3–CH=CH–CH3 (but-2-ene) · must show C=C bond between C2 and C3, All atoms and bonds shown

(b) but-2-ene

Common mistakes: Drawing but-1-ene instead of but-2-ene

Show mark scheme and worked solution

Marking points

B1 (a) · 2 marks · Diagrams correct displayed structure with C=C between the second and third carbon: CH3CH=CHCH3, all bonds shown.

B1 (b) · 1 mark · Names the isomer as but-2-ene.

Worked solution

(a) Displayed formula: With all atoms and correct double bond clearly shown between C2 and C3.

(b) The name is but-2-ene.