The name for `HC-=C-underset(CH_(3))underset(|)(C)=CH-CH_(3)` is :-

Options

A. 3-Methyl-2-penten-4-yne
B. 3-Methyl-3-penten-1-yne
C. 3-Methyl-4-pentyn-1-ene
D. 3-Methyl pentenyne

Answer

To determine the IUPAC name for the compound `HC≡C-CH(CH₃)-C=CH-CH₃`, we will follow the systematic approach for naming organic compounds that contain both double and triple bonds.

### Step-by-Step Solution:

1. **Identify the Longest Carbon Chain**:
- The longest continuous carbon chain that includes both the triple bond (alkyne) and the double bond (alkene) consists of 5 carbon atoms.

2. **Number the Carbon Chain**:
- Start numbering the carbon chain from the end closest to the triple bond to give it the lowest possible number.
- The numbering will be as follows:
- C1: HC≡C (triple bond)
- C2: CH
- C3: C(CH₃) (methyl group attached)
- C4: C=CH (double bond)
- C5: CH₃

3. **Identify the Functional Groups**:
- The compound has a triple bond (alkyne) and a double bond (alkene).
- The triple bond takes precedence over the double bond in naming.

4. **Assign Locants to the Functional Groups**:
- The triple bond is at position 1 (C1).
- The double bond is at position 4 (C4).
- The methyl group is at position 3 (C3).

5. **Construct the Name**:
- According to IUPAC nomenclature, we list the substituents in alphabetical order, followed by the parent chain name.
- The name will be constructed as follows:
- The substituent is "3-methyl".
- The parent chain is "pent" (for 5 carbons).
- The suffix for the double bond is "ene" and for the triple bond is "yne".
- Since the triple bond takes precedence, we will name it as "1-yne" and "4-ene".

6. **Final Name**:
- Combine all parts: "3-methyl-4-pentene-1-yne".

Thus, the IUPAC name for the compound is **3-methyl-4-pentene-1-yne**.