Question

What is the IUPAC name for the following compound?

a. 5-chloro-3-methylhexanone
b. 2-chloro-4-methyl-5-hexanone
c. 5-chloro-3-methyl-2-hexanone
d. 5-chloro-3,5-dimethyl-2-pentanone
e. 1-chloro-1,3-dimethyl-4-pentanone

Answer 1

Answer:

c. 5-chloro-3-methyl-2-hexanone

Explanation:

The IUPAC nomenclature of alkanes are given as follows:

• Select the longest possible carbon chain.
• For the number of carbon atom, we add prefix as 'meth' for 1, 'eth' for 2, 'prop' for 3, 'but' for 4, 'pent' for 5, 'hex' for 6, 'sept' for 7, 'oct' for 8, 'nona' for 9 and 'deca' for 10.
• A suffix '-ane' is added at the end of the name.
• If two of more similar alkyl groups are present, then the words 'di', 'tri' 'tetra' and so on are used to specify the number of times these alkyl groups appear in the chain.

For any substituent attached, the numbering is done according to the priority of the functional group which is:-

Carboxylic Acids  > Acid Anhydrides   >  Esters    > Acyl Halides   > Amides   > Nitriles   >  Aldehydes    > Ketones   > Alcohols   > Thiols   > Amines   > Ethers   >  Sulphides   > Alkenes   > Alkynes   > Alkyl Halides   > Nitro   > Alkanes

Thus,

Numbering is shown below. The long chain is 6 membered ring having substituents ketone at C-2, methyl group at C-3 and chloro bond at C-5

The name is:-

c. 5-chloro-3-methyl-2-hexanone