Naming Carbonyl Compounds Continued
Example: Naming Carbonyl Compounds
Question
Give the IUPAC name for the following compound:
\(\text{CH}_{3}\text{CH}_{2}\text{CH}(\text{CH}_{3})\text{CH}_{2}\text{CH}_{2}\)\(\color{red}{\textbf{COOH}}\)
(Remember that the side groups are shown in brackets after the carbon atom to which they are attached)
Draw the structural representation
Identify the functional group
The compound has a \(-\text{COOH}\) functional group. It is therefore a carboxylic acid and the suffix is -oic acid.
Find the longest carbon chain containing the functional group
There are six carbon atoms in the longest chain containing the functional group. The prefix for this compound is hexan-.
Number the carbon atoms in the carbon chain
The carbon atoms should be numbered from right to left so that the carboxylic acid functional group has the lowest numbered carbon atom.
Look for any branched groups, name them and give their position on the carbon chain
There is a branched group attached to the fourth carbon atom. This group has only one carbon atom and is therefore a methyl group (4-methyl).
Combine the elements of the compound's name into a single word in the order of branched groups; prefix; name ending according to the functional group
The compound's name is 4-methylhexanoic acid.
Example:
Question
Give the IUPAC name for the following compound:
\(\text{CH}_{3}\)\(\color{red}{\text{COO}}\)\(\text{CH}_{2}\text{CH}_{2}\text{CH}_{2}\text{CH}_{3}\)
Identify the functional group
The compound has a \(-\text{COO}\) functional group. It is therefore an ester and the suffix will be -oate. This can also be shown as:
Determine which part is from the alcohol and which is from the carboxylic acid
The left half of the compound contains the carbonyl group and is therefore from the carboxylic acid. The right half of the compound must be from the alcohol.
Determine the number of carbon atoms in each chain
There are 2 carbon atoms in the part that contains the C\(=\)O group (from the carboyxlic acid), therefore the prefix is ethan-. There are 4 carbon atoms in part of the chain without the carbonyl group (from the alcohol), which is therefore butyl.
Look for any branched groups, name them and give their position on the carbon chain
There are no branched groups.
Combine the elements of the compound's name into a single word in the order of name of chain from the alcohol; prefix (from chain containing carbonyl functional group); suffix
The compound's name is butyl ethanoate.
Optional Activity: Building Molecules
Using atomic model kits build molecules of butane, but-1-ene, but-1-yne, butan-1-ol, butanoic acid, butyl butanoate, butan-2-one, butanal. If you don't have an atomic model kit remember that you can use jelly tots (or playdough) and toothpicks. Use different colour jelly tots to represent the different atoms and extra toothpicks to represent double and triple bonds.
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Identify the functional group in each of these molecules. Move the functional group around the molecule. You should find that you can do so with but-1-ene, but-1-yne and butan-1-ol. It will not be possible with butanoic acid and there is no functional group to move in butane.
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Can you see that if you move the carbonyl group in butan-2-one you will either still get butan-2-one or you will get butanal? Similarly, when moving the carbonyl group in butanal you can only get butanal or butan-2-one.
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Build a model of the molecule below:
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Compare this to butyl butanoate. What differences are there between these two molecules? What similarities are there? What is the name of the new molecule?
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Continue by building different compounds for your friends. Make them identify the functional group, the number of carbon atoms and therefore the name of the compound.
This lesson is part of:
Organic Molecules