Structures and names of some hydrocarbons are given below. Explain why the names given in parenthesis are not correct :

Explanation

(a) `overset(1)(C)H_3 -overset(2)(C)H_2 - underset(underset(C_2 H_5)|)overset(3)CH - overset(4)CH_2 - underset(underset(CH_3)|)overset(5)CH - overset(6)CH_2 - overset(7)CH_3`
3 - Ethyl-5-methylheptane
Both the substituents ethyl and methyl are in equivalent positions. Lower number is given to the one that comes first in the name according to alphabetical order.
(b) `overset(1)(C)H_3 -underset(underset(CH_3)|)overset(2)(C)H -underset(underset(CH_3)|) overset(3)CH - overset(4)CH_2 - overset(5)CH_3`
2,3-Dimethylpentane
Numbering is done from the end which gives lower number to the substituents.
(c ) `overset(6)CH_3 - underset(underset(CH_3)|)overset(5)CH - overset(4)CH_2 - underset(underset(CH_3)|)overset(3) CH - underset(underset(CH_3)|)overset(2)CH - overset(1)CH_3`
2,3,5- Trimethylhexane
Lowest locant number 2, 3, 5 is lower than 2, 4, 5.
(d)
5-(2- Ethylbutyl) -3, 3-dimethyldecane
Larger number of substituents are attached to the parent chain.
(e)
2, 3, 5-Trimethyl-4-propylheptane
Larger number of substituents are attached to the parent chain.