Question

The IUPAC name of ethyl isopropyl ketone is

• A. $2-\mathrm{methyl}-3-\mathrm{pentanone}$
• B. $4-\mathrm{methyl}-3-\mathrm{pentanone}$
• C. $4,4-\mathrm{dimethyl}-3-\mathrm{butanone}$
• D. $1,1-\mathrm{dimethyl}-2-\mathrm{butanone}$

Answer 1

The correct option is A

$2-\mathrm{methyl}-3-\mathrm{pentanone}$

Explanation for correct option

(A) $\mathbf{2}\mathbf{-}\mathbf{methyl}\mathbf{-}\mathbf{3}\mathbf{-}\mathbf{pentanone}$

IUPAC System of Nomenclature

• Find the carbon chain that is the longest.
• All of the substituents must be identified.
• From the end of the parent chain, count the carbons until the substituents have the lowest number.
• A prefix indicates how many times a substituent group appears (di, tri, tetra, etc.).
• A suffix or other element(s) indicates the presence of functional groups in the compound.
• If there are two or more substituents, they are listed alphabetically by base name.

Ethyl isopropyl ketone

• Structure of ethyl isopropyl ketone:

• The parent chain consists of five carbon atoms, hence the word root is pent.
• The suffix used for the ketone functional group is -one.
• Therefore, the UPAC name is $2-\mathrm{methyl}-3-\mathrm{pentanone}$.

Explanation for incorrect options

• The IUPAC name of ethyl isopropyl ketone is $2-\mathrm{methyl}-3-\mathrm{pentanone}$. Hence all other options (B), (C) and (D) are incorrect.

Therefore, the correct option is (A) $\mathbf{2}\mathbf{-}\mathbf{methyl}\mathbf{-}\mathbf{3}\mathbf{-}\mathbf{pentanone}$.