Introduction to Organic Chemistry
6 marks · NormalButene and butanol are both organic compounds. Draw the displayed formula for butanol.
Explain how you use the structure to identify the correct IUPAC name for butanol.
Describe one key difference in the structure and naming between butene and butanol.
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(a) — · must show Four carbon backbone, –OH group on either terminal or internal carbon, Correct hydrogens and bonds
(b) — · must show Identify longest chain (four carbons), Locate the position of the –OH group, Name as butan-1-ol or butan-2-ol using position number
(c) — · must show Butene contains a C=C double bond (alkene), Butanol contains an –OH group (alcohol), Naming: butene uses -ene suffix, butanol uses -ol suffix
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Marking points
B1 (a) · 2 marks · Displayed formula of butanol with four carbon atoms and a hydroxyl group (-OH), other bonds correctly filled with hydrogens
B2 (b) · 2 marks · Correctly explains the logic for naming butanol: identifies main chain and position of –OH, gives correct IUPAC name (butan-1-ol or butan-2-ol)
B3 (c) · 2 marks · Describes the structural and naming difference between an alkene (C=C) and an alcohol (–OH); discusses suffix change
Worked solution
(a) The displayed formula for butanol shows a chain of four carbon atoms, with an –OH group on one carbon, the rest bonded to hydrogens. For butan-1-ol:
For butan-2-ol:
(b) To name butanol, find the longest carbon chain with the –OH group attached. Use the position of the –OH to select butan-1-ol (if at the end) or butan-2-ol (if on the second carbon). Number the chain from the end closest to the –OH group.
(c) Butene is an alkene containing a carbon–carbon double bond; its names end in -ene. Butanol is an alcohol with an –OH group; its names end in -ol. Structurally, butene is unsaturated; butanol is a saturated alcohol.