Question

Write the IUPAC names of the following compounds:
a) $C{H_3} - C{H_2} - Br$
b) $HCHO$

Answer 1

IUPAC nomenclature is basically based on naming the longest chain of carbons connected through single bonds, double bonds and triple bonds present in an organic molecule. The longest chain of carbon can be in a chain as well in a ring form. The functional group present is used as the suffix of the name. Other groups called the substituents will be used as the prefix of the name.

Complete solution:
a) $C{H_3} - C{H_2} - Br$
First, we will identify the longest chain also known as the parent chain.
Here the longest name is made up of two carbons. This is known as the root word of the organic compound which represents the total number of carbons. So here the root will be ‘eth’ and since only single bonds are present, we will use ‘and’ so the word will be ‘ethane’.
Now the substituent present is the bromine group which is present on the first position. So, we will use ‘bromo’ in the prefix of the root word.
Therefore, the IUPAC name will be $1 -$ bromoethane
b) $HCHO$
Here we see that only one carbon is present so the root word will be ‘meth’ and since only single bond is present, we’ll use ‘and’ so the root word will be ‘methane’
Now the functional group present is of an aldehyde so we will use ‘al’ in the suffix.
Therefore, the IUPAC name will be methanal.

Note: We write it as ‘methanal’ and not as ‘methane-al’ as two vowels are present simultaneously which cannot be used according to the rules of IUPAC nomenclature. Methanal is commonly known as formaldehyde. Also, if any functional group or substituent is present on the first position of the carbon chain, it is not necessary to mention that in the IUPAC name. so, we can also write Bromoethane.