The IUPAC name of dimethylacetylene is

Options

A. propyne
B. ethyle acetylene
C. But-1-yne
D. But-2-yne

Answer

To determine the IUPAC name of dimethylacetylene, we can follow these steps:

### Step 1: Identify the Structure
Dimethylacetylene consists of an acetylene (ethyne) backbone with two methyl (CH₃) groups attached. The structure can be represented as:
\[ \text{CH}_3 - \text{C} \equiv \text{C} - \text{CH}_3 \]

### Step 2: Count the Carbon Atoms
In the structure, there are a total of 4 carbon atoms:
- 2 from the methyl groups
- 2 from the acetylene backbone

### Step 3: Determine the Longest Carbon Chain
The longest continuous chain of carbon atoms in this compound is 4, which gives us the base name "butane."

### Step 4: Identify the Type of Bond
Since there is a triple bond (indicated by the "≡") between the second and third carbon atoms, we need to indicate this in the name. The presence of a triple bond in a hydrocarbon is denoted by the suffix "-yne."

### Step 5: Number the Carbon Atoms
We need to number the carbon atoms in such a way that the triple bond gets the lowest possible number. Starting from either end, we can number the carbon atoms as follows:
1. C1: CH₃
2. C2: C (part of the triple bond)
3. C3: C (part of the triple bond)
4. C4: CH₃

The triple bond starts at carbon 2.

### Step 6: Combine the Information
Now, we can combine the information:
- The base name is "but" (for 4 carbons).
- The position of the triple bond is at carbon 2.
- The suffix for the triple bond is "-yne."

Thus, the IUPAC name is **but-2-yne** (or 2-butyne).

### Final Answer
The IUPAC name of dimethylacetylene is **but-2-yne**.

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