Question

IUPAC name of the given structures are:

A.(i) hexane, (ii) 3-methylbutane

B.(i) isopentane, (ii) 2,2-dimethylbutane

C.(i) 3-ethylbutane, (ii) isopentane

D.(i) 3-methylpentane, (Ii) 2-methylbutane

Answer 1

Hint:
Try solving this question selecting the main chain, numbering it and choosing the root word. The main chain is the one with the greatest number of carbons. Numbering in IUPAC is done such that the branched atom gets the lowest number.

Complete step by step answer:
Let us start naming the organic compound according to the rules of IUPAC nomenclature –
For compound (i) –
Let us number the given compound.

As we can see, there are a total of 5 carbon atoms. So, the root word will be ‘pent’.
This compound only has single bonds. So, it is an alkane. The name now becomes ‘pentane’.
As we can see, there is a carbon we haven’t included. This is also known as an alkyl group. Therefore, we will add it in prefix. Since it is attached to carbon-3, the prefix will be ‘3-methyl’.
The name of the compound is – ‘3-methylpentane’
For compound (ii) –
Let us number the given compound.

As we can see, there are a total of 4 carbon atoms. So, the root word will be ‘but’.
This compound only has single bonds. So, it is an alkane. The name now becomes ‘butane’.
As we can see, there is a carbon we haven’t included. This is also known as an alkyl group. Therefore, we will add it in prefix. Since it is attached to carbon-2, the prefix will be ‘2-methyl’.
The name of the compound is – ‘2-methylbutane’.
Therefore, the answer is – option (d).
Additional Information: Alkanes are known as saturated hydrocarbons, whereas alkenes and alkynes are known as unsaturated hydrocarbons.

Note:
The table for root words of organic compound according to the number of carbons is as follows –

Number of Carbons	Root word
1	Meth
2	Eth
3	Prop
4	But
5	Pent
6	Hex
7	Hept
8	Oct
9	Non
10	Dec
11	Undec
12	Dodec