Step 1: Understanding the Question:
The problem presents an addition reaction of a hydrohalic acid (HI) across the double bond of an unsymmetrical alkene (3-methylhex-3-ene) and requires us to predict the major product using IUPAC nomenclature guidelines.
Step 2: Key Formula or Approach:
The addition of hydrogen halides to unsymmetrical alkenes proceeds via electrophilic addition following
Markovnikov's rule. The electrophile ($\text{H}^+$) adds to the double-bonded carbon to form the more stable carbocation intermediate (preferring tertiary over secondary), followed by nucleophilic attack by the halide ion ($\text{I}^-$).
Step 3: Detailed Explanation:
The starting alkene 3-methylhex-3-ene features a double bond between carbon-3 and carbon-4:
$$\text{CH}_3-\text{CH}_2-\text{C(CH}_3\text{)=CH}-\text{CH}_2-\text{CH}_3$$
Carbon-3 is attached to a methyl group and an ethyl group, making it a highly substituted olefinic carbon.
Carbon-4 is attached to a single hydrogen atom and an ethyl group.
When $\text{H}^+$ adds to carbon-4, a highly stable $3^\circ$ carbocation is formed at carbon-3. Then, the iodide nucleophile ($\text{I}^-$) attacks this tertiary carbocation.
The resulting structure is:
$$\text{CH}_3-\text{CH}_2-\text{C(I)(CH}_3\text{)}-\text{CH}_2-\text{CH}_2-\text{CH}_3$$
Numbering the longest continuous six-carbon chain from the left side gives a methyl group and an iodo group both located at position 3. Therefore, the systematic IUPAC name is
3-iodo-3-methylhexane.
Step 4: Final Answer:
The major product is 3-Iodo-3-methylhexane, which corresponds to option (C).