Question

How would you name the following compounds?
(i) $CH_{ 3 }-CH_{ 2 }Br$
(ii) $H-CHO$
(iii) $CH_3-(CH_2 )_3-CH=CH_2$
A- (i)Bromoethane (ii) Methanol (iii) Hexene
B- (i)Bromoethane (ii) Methanol (iii) Hexane
C- (i)Bromopropane (ii) Methanol (iii) Hexene
D- (i)Bromoethane (ii) Methanal (iii) Hexene

Answer 1

Hint: Follow the IUPAC rules of nomenclature. Identify whether a given group is a functional group or substituent and then name them accordingly. If the position of the functional group or substituent is at the start of the chain then we ignore position number in the name.

Complete answer:
We know that the IUPAC name is given based on the chain containing the largest number of carbon atoms and the largest number of functional groups. In the given compounds all are straight-chain compounds with no other side chains.
In the first compound, there is a halogen group. Halogen group is a substituent, not a functional group. So its name will be at the start of the IUPAC name. Given compound contains 2 carbon atoms and there are no functional groups so the name will end with ethane. The position of the bromine atom will be 1 as we start numbering from the carbon which contains bromine atom. IUPAC's name will be 1-bromoethane. Which can also be called bromoethane.
In the second compound, there is just one carbon atom with one functional group. Considering the number of hydrogen atoms on the carbon given functional group is the aldehyde group. The carbon chain name will be methane and the functional group name would be al. IUPAC name is methanol.
In the third compound, there are 6 carbon atoms in the parent chain and no other sub-chains. There is one double bond in the compound. It is at the start of the chain. Its IUPAC name would be hexene.
Therefore, option D is correct.

Note: We should give numbers to the position of substituents or functional groups such that their position is least. If any functional group position is not mentioned means it will be at the start of the chain.