Question

(a) Give the IUPAC name for the following organic compounds: 

 

Hint:

When numbering the carbon chain, always give the functional group (like the -OH or the double bond) the lowest possible number!

Answer 1

(1) The structure shown is:
HO-CH(CH₃)-CH₂-CH₃

To find the IUPAC name, we first select the longest carbon chain containing the carbon attached to the -OH group.
The longest chain has 4 carbon atoms, so the parent name is butane.
Since the functional group is alcohol, we use the suffix -ol.
The -OH group is attached to the second carbon atom.

Therefore, the IUPAC name is butan-2-ol.

(2) The structure shown is:
CH₃-CH₂-CH(CH₃)-CH₂-CH₃

Here, the longest continuous carbon chain has 5 carbon atoms, so the parent hydrocarbon is pentane.
There is one methyl group (-CH₃) attached to the third carbon atom.

Therefore, the IUPAC name is 3-methylpentane.

Final Answers:
1. Butan-2-ol
2. 3-Methylpentane

Quick Explanation:
In IUPAC naming, first identify the longest carbon chain.
Then locate the functional group or substituent.
Number the chain in such a way that the functional group gets the lowest possible number.
For alcohols, the -OH group gets priority in numbering.