The IUPAC name of the compound
`C_(2)H_(5)-underset(CH_(2))underset(||)(C)-CH_(2)OH`

Options

A. 2 - Ethyl prop-2- ene-1 -ol
B. 2- Hydroxymethyl butan-1 -ol
C. 2- Methylene butan-1 -ol
D. 2- Ethyl - 3hydroxyprop-1 -ene

Answer

To determine the IUPAC name of the compound `C2H5-CH2=C-CH2OH`, we will follow these steps:

### Step 1: Identify the longest carbon chain
The compound has a total of 5 carbon atoms, which can be arranged as follows:
- C2H5 (ethyl group)
- CH2 (next carbon)
- C (double bond with CH2)
- CH2OH (hydroxyl group)

The longest continuous chain includes all 5 carbon atoms.

### Step 2: Number the carbon chain
We will number the carbon chain starting from the end closest to the functional group (the hydroxyl group -OH). This gives us:
1. CH2OH (C1)
2. C (C2)
3. CH2 (C3)
4. C2H5 (C4)
5. C (C5)

### Step 3: Identify functional groups and substituents
- The hydroxyl group (-OH) is at carbon 1.
- There is a double bond between carbon 2 and carbon 3.
- The ethyl group (C2H5) is a substituent on carbon 2.

### Step 4: Assign locants and name the compound
- The longest chain is a 5-carbon chain with a double bond and a hydroxyl group.
- The main chain is named as "pent" since it has 5 carbons.
- The double bond is located between carbons 2 and 3, so we denote it as "pent-2-ene".
- The hydroxyl group is on carbon 1, so we add "1-ol" to indicate the presence of the alcohol functional group.
- The ethyl group is at carbon 2, so we denote it as "2-ethyl".

### Step 5: Combine all parts for the IUPAC name
Putting it all together, we get:
- The full IUPAC name is **2-ethylpent-2-en-1-ol**.

### Final Answer:
**2-ethylpent-2-en-1-ol**

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