Question

The incorrect IUPAC name is:

• A. $C{H}_3-CO-CH\left(C{H}_3\right)-C{H}_3$ : 2-methyl-3-butanone
• B. $C{H}_3-CH\left(C{H}_3\right)-CH\left(C{H}_{2}C{H}_3\right)-C{H}_3$ : 2,3-dimethylpentane
• C. $C{H}_3-C$$\equiv$$C-CH\left(C{H}_3\right)$ 2,4-Methyl-2-pentyne
• D. $C{H}_3-CH\left(Cl\right)-CH\left(Br\right)-C{H}_3$ : 2-bromo-3-chlorobutane

Answer 1

The correct option is A $C{H}_3-CO-CH\left(C{H}_3\right)-C{H}_3$ : 2-methyl-3-butanone

in the first option, numbering should be done from left-hand side as the functional group get the least numbering from the left-hand side. hence option A is correct.
Option B is correctly named as it has 5 carbon in the longest chain and two methyl groups. numbering is done from the left-hand side.
Option C is correctly named, numbering from the left side as triple bond gets the least number
option D is also correctly named when numbered from right-hand side bromine gets the least number, which is correct because when halogens are at symmetric positions then numbering should be least for the element which comes first in alphabetical order.
Thus, option A is the right answer as we have to pick the incorrect answer.