Organic Chemistry
8 marks · NormalThis question is about the structures of alcohols and carboxylic acids.
Draw the displayed formula for propan-1-ol.
Draw the displayed formula for propanoic acid.
Give the molecular formula for butan-1-ol.
How many carbon atoms are in a molecule of methanoic acid?
Explain in one sentence how the name of an alcohol or a carboxylic acid indicates the number of carbon atoms in the molecule.
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) Displayed formula for propan-1-ol: CH3–CH2–CH2–OH, all bonds shown, O–H bond drawn. · must show Three carbon chain, with –OH group on end carbon and H atoms correctly shown., All bonds shown, including O–H.
(b) Displayed formula for propanoic acid: CH3–CH2–COOH, all bonds shown, COOH group drawn with double bond to O and single bond to OH. · must show Three carbon chain, –COOH at end, all bonds shown, double bond O and single bond O–H.
(c) C4H10O
(d) 1
(e) The stem of the name (meth-, eth-, prop-, but-) tells how many carbon atoms are present; carboxylic acids always have the COOH group at the end. · must show name stem gives number of carbons, COOH group always at end for acids
Show mark scheme and worked solution
Marking points
A1 (a) · 2 marks · Award 2 marks for a fully correct displayed formula for propan-1-ol with all bonds shown, including O–H. Award 1 mark for correct structure but incomplete or missing bonds.
A2 (b) · 2 marks · Award 2 marks for a fully correct displayed formula for propanoic acid with all bonds shown, COOH group detailed with double bond O and single bond O–H. Award 1 mark for correct structure but incomplete or missing bonds.
B1 (c) · 1 mark · C4H10O only.
B2 (d) · 1 mark · One only.
E1 (e) · 2 marks · 1 mark for mentioning the name stem gives carbon number, 1 mark for stating COOH group is always at end (for acids) or –OH group position is specified (for alcohols).
Worked solution
a) Propan-1-ol displayed formula:
b) Displayed formula for propanoic acid:
c) Butan-1-ol: its molecular formula is C4H10O.
d) Methanoic acid has one carbon atom.
e) The stem of the compound's name (such as meth-, eth-, prop-, but-) tells how many carbon atoms are present in the molecule. For carboxylic acids, the COOH group is always attached to the end carbon in the chain.