A quick introductory look at the alcohols
5 marks · HardThis question is about alcohols.
State the functional group present in all alcohols.
Give the displayed formula for the functional group found in alcohols.
A student draws the following structural formula:
Identify the functional group in this compound and describe its role in classifying this molecule as an alcohol.
Explain why different alcohols have similar chemical properties, referring to their structure.
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) Hydroxyl group or -OH group.
(b) -OH, drawn as the group attached to a carbon atom (displayed formula: —O—H).
(c) The functional group is -OH (hydroxyl group). It is this group that classifies the compound as an alcohol, as all alcohols contain this group attached to a carbon atom.
(d) Alcohols have similar chemical properties because each contains the same functional group (-OH), which determines their reactions.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States hydroxyl or -OH group as the functional group in all alcohols.
B2 (b) · 1 mark · Gives correct displayed formula: —O—H or equivalent (-OH attached to a carbon atom).
B3 (c) · 1 mark · Identifies -OH as the functional group in CH3CH2OH.
B4 (c) · 1 mark · States that the -OH group is why it is classed as an alcohol.
B5 (d) · 1 mark · Explains that having the same functional group gives similar chemical properties.
Worked solution
a) The functional group in all alcohols is the hydroxyl group, written as -OH.
b) The displayed formula for the functional group is:
c) In \ce{CH3CH2OH}, the -OH group is present. This -OH is the functional group that makes it an alcohol.
d) All alcohols react similarly because they have the same -OH group (hydroxyl), which determines how they react chemically.