In order to give compounds a name, certain rules must be followed. When naming organic compounds, the IUPAC (International Union of Pure and Applied Chemistry) nomenclature is used. We will first look at some of the steps that need to be followed when naming a compound, and then try to apply these rules to some specific examples.
STEP 1: Recognise the functional group in the compound. This will determine the suffix (the ’end’) of the name. For example, if the compound is an alkane, the suffix will be -ane; if the compound is an alkene the suffix will be -ene; if the compound is an alcohol the suffix will be -ol, and so on.
STEP 2: Find the longest continuous carbon chain (it won’t always be a straight chain) and count the number of carbon atoms in this chain. This number will determine the prefix (the ’beginning’) of the compound’s name. So, for example, an alkane that has 3 carbon atoms will have the suffix prop and the compound’s name will be propane.
STEP 3: Number the carbons in the longest carbon chain (Important: If there is a double or triple bond, you need to start numbering so that the bond is at the carbon with the lowest number.
STEP 4: Look for any branched groups and name them. Also give them a number to show their position on the carbon chain. If there are no branched groups, this step can be left out.
STEP 5: Combine the elements of the name into a single word in the following order: branched groups; prefix; name ending according to the functional group and its position along the longest carbon chain.
Question: Give the IUPAC name for the following compound:
Answer
Step 1 : Identify the functional group
The compound is an alkane and will have the suffix -ane.
Step 2 : Find the longest carbon chain
There are three carbons in the longest chain. The prefix for this compound is -prop.
Step 3 : Number the carbons in the carbon chain
If we start at the carbon on the left, we can number the atoms as shown below:
Step 4 : Look for any branched groups, name them and give their position on the carbon chain
There is a branched group attached to the second carbon atom. This group has the formula CH3 which is methane. However, because it is not part of the main chain, it is given the suffix -yl (i.e. methyl). The position of the methyl group comes just before its name (see next step).
Step 5 : 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 2-methylpropane.
STEP 1: Recognise the functional group in the compound. This will determine the suffix (the ’end’) of the name. For example, if the compound is an alkane, the suffix will be -ane; if the compound is an alkene the suffix will be -ene; if the compound is an alcohol the suffix will be -ol, and so on.
STEP 2: Find the longest continuous carbon chain (it won’t always be a straight chain) and count the number of carbon atoms in this chain. This number will determine the prefix (the ’beginning’) of the compound’s name. So, for example, an alkane that has 3 carbon atoms will have the suffix prop and the compound’s name will be propane.
STEP 3: Number the carbons in the longest carbon chain (Important: If there is a double or triple bond, you need to start numbering so that the bond is at the carbon with the lowest number.
STEP 4: Look for any branched groups and name them. Also give them a number to show their position on the carbon chain. If there are no branched groups, this step can be left out.
STEP 5: Combine the elements of the name into a single word in the following order: branched groups; prefix; name ending according to the functional group and its position along the longest carbon chain.
Question: Give the IUPAC name for the following compound:
Answer
Step 1 : Identify the functional group
The compound is an alkane and will have the suffix -ane.
Step 2 : Find the longest carbon chain
There are three carbons in the longest chain. The prefix for this compound is -prop.
Step 3 : Number the carbons in the carbon chain
If we start at the carbon on the left, we can number the atoms as shown below:
Step 4 : Look for any branched groups, name them and give their position on the carbon chain
There is a branched group attached to the second carbon atom. This group has the formula CH3 which is methane. However, because it is not part of the main chain, it is given the suffix -yl (i.e. methyl). The position of the methyl group comes just before its name (see next step).
Step 5 : 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 2-methylpropane.
