Organic Chemistry
8 marks · NormalAnswer all parts.
Give the IUPAC name for the compound with the displayed formula:
Refinery gases are produced during the separation of crude oil. Name one typical use of refinery gases.
The compound below has a side chain. Use IUPAC conventions to name it.
Refinery gases, gasoline and other fractions are obtained from crude oil by a particular process. Name this process and briefly describe how compounds are separated during it.
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.
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(a) Butane
(b) Used as liquefied petroleum gas (LPG) for heating or cooking.
(c) 2-methylbutane
(d) Fractional distillation. Crude oil is heated and its vapours pass up a column. Hydrocarbons condense at different levels based on their boiling points; smaller molecules with lower boiling points condense higher up, larger molecules condense lower down.
Also accept: 3-methylbutane; 2-methylbutane
Common mistakes: Incorrectly numbering the main carbon chain; Incorrect branch or fraction uses
Show mark scheme and worked solution
Marking points
B1 (a) · 2 marks · Correctly names the 4-carbon straight chain compound as butane.
B2 (b) · 1 mark · Gives a typical use of refinery gases, e.g., LPG for heating/cooking.
B3 (c) · 2 marks · Correctly names branched compound as 2-methylbutane using IUPAC rules.
B4 (d) · 1 mark · Correctly names 'fractional distillation' as the process.
A1 (d) · 1 mark · Mentions compounds separated based on boiling points.
A2 (d) · 1 mark · Describes that smaller/lower-boiling condense near the top, larger/higher-boiling at the bottom.
Worked solution
a) The compound shown is butane. b) Refinery gases are used as LPG for home heating and cooking. c) The compound with a main chain of 4 carbons and a methyl on the 2nd carbon is called 2-methylbutane. d) The process is fractional distillation. Crude oil is heated so it vaporises; vapours rise up a fractionating column. Fractions condense at different heights depending on boiling point: lower boiling hydrocarbons condense higher up, and those with higher boiling points condense at lower levels.