The IUPAC name for CH$_{3}$CHCH$_{3}$CHCLCHCH$_{3}$CH$_{2}$CH$_{3}$ is

Analyze the question

The formula is CH₃CH(CH₃)CHClCH(CH₃)CH₂CH₃. We need to find the main chain, number it, and name the substituents.

Structure

Writing it out carbon by carbon:

• C1: CH₃
• C2: CH (with a CH₃ branch)
• C3: CHCl
• C4: CH (with a CH₃ branch)
• C5: CH₂
• C6: CH₃

The longest chain has 6 carbons, so the parent is hexane. The substituents are two methyl groups and one chlorine.

Numbering

The rules for numbering are:

1. Give the lowest set of locants to all substituents together.
2. Name the substituents in alphabetical order (chloro before methyl; "di" is ignored for alphabetising).

• Numbering from the left: substituents are at 2 (methyl), 3 (chloro), 4 (methyl), so the locant set is {2,3,4}.
• Numbering from the right: C1 = CH₃, C2 = CH₂, C3 = CH(CH₃), C4 = CHCl, C5 = CH(CH₃), C6 = CH₃. The locants are {3,4,5}.

{2,3,4} is lower, so we number from the left.

Name

• Chloro at C3
• Methyl at C2 and C4

Alphabetical order puts chloro first: 3-chloro-2,4-dimethylhexane

Checking the options

• A: The locants are right, but the alphabetical order is wrong (it lists methyl before chloro).
• B: The numbering is wrong.
• C: The numbering is wrong (4-chloro-3,5-dimethyl).
• D: 3-chloro-2,4-dimethylhexane. This is correct.

Tip: First find the longest chain. Then number so the substituent locants are as low as possible, and write the names alphabetically (ignoring di-, tri-). Option A is a common trap: the numbers are correct, but the name is not in alphabetical order.