Question

Explain how hydrocarbons containing an OH group are named.

Short answer

To name hydrocarbons containing an OH group (alcohols), first identify the longest continuous carbon chain (parent chain) and number the carbon atoms starting from the end closest to the hydroxyl group. Replace the -e at the end of the alkane base name with -ol (e.g., methanol, ethanol, propanol, butanol, etc.). Identify and name any substituents (e.g., methyl, ethyl, propyl, etc.), include their position numbers, and list them in alphabetical order. Finally, combine in the order: substituent names, base name of the parent chain, and the position number of the hydroxyl group followed by -ol (e.g., 2-methyl-3-propanol).

Step-by-step solution

Identify the parent chain

Firstly, identify the longest continuous carbon chain in the molecule, which is called the parent chain. This chain will determine the base name of the compound.

Identify and name the functional group

Since the exercise is about hydrocarbons with an OH group, the functional group of interest is the hydroxyl (OH) group. Compounds containing a hydroxyl group are called alcohols.

Determine the position of the functional group

Number the carbon atoms in the parent chain, starting from the end closest to the hydroxyl group. The number of the carbon atom to which the OH group is attached should be as low as possible. This number will denote the position of the hydroxyl group.

Name the parent chain

Name the parent chain based on the number of carbon atoms, using the appropriate alkane name (e.g., methane, ethane, propane, butane, etc.) and replace the -e at the end of the alkane name with -ol to indicate the presence of the OH group (e.g., methanol, ethanol, propanol, butanol, etc.).

Identify and name substituents

If there are any other substituents (like alkyl groups or halogens) present on the carbon chain, identify them and assign a number to their position on the parent chain. Use prefixes (e.g., methyl, ethyl, propyl, etc.) to name the substituents and include their position numbers.

Combine all parts of the name

Combine all parts of the name in the following order: the substituent names (including their position numbers, listed in alphabetical order if there are multiple substituents), the base name of the parent chain, and the position number of the hydroxyl group followed by the -ol suffix. For example, a compound with a four-carbon chain, hydroxyl group on the second carbon, and a methyl group on the third carbon would be named 2-methyl-3-propanol. By following these steps, you can accurately name hydrocarbons containing an OH group according to the IUPAC nomenclature system.