Common name of `CH_(2)=CH-CN` is :-
(a) acrylonitrile
(b) vinyl cyanide
(c ) allyl cyanide
(d) allyl nitrile

Options

A. a, b and d
B. a and b
C. only b
D. a, b and c

Answer

To determine the common name of the compound `CH2=CH-CN`, we will follow these steps:

### Step 1: Identify the structure of the compound
The given compound is `CH2=CH-CN`. This indicates that there is a double bond between the first two carbon atoms (C1 and C2) and a cyanide group (CN) attached to the third carbon atom (C3).

### Step 2: Analyze the functional groups
In this compound, the cyanide group (–C≡N) is the functional group. The presence of the double bond suggests that we are dealing with an alkene.

### Step 3: Determine the longest carbon chain
The longest carbon chain in this compound consists of three carbon atoms (C1, C2, and C3).

### Step 4: Name the compound based on IUPAC rules
According to IUPAC nomenclature, the base name for a three-carbon alkene is "propene." Since there is a cyanide group attached, we need to modify the name to reflect this functional group. The compound can be named as "prop-2-enenitrile" based on the position of the double bond and the cyanide group.

### Step 5: Identify common names
The common names for this compound include:
- **Acrylonitrile**: This is a widely accepted common name for the compound.
- **Vinyl cyanide**: This name is also acceptable as it describes the vinyl group (C=C) and the cyanide group.
- **Allyl cyanide**: This name is incorrect because the allyl group is typically represented as CH2=CH-CH2-, which does not match our compound.
- **Allyl nitrile**: This name is also incorrect for the same reason as above.

### Conclusion
The common names that apply to `CH2=CH-CN` are acrylonitrile and vinyl cyanide. However, since the question asks for the most common name, the answer is **(a) acrylonitrile**.

### Final Answer
The common name of `CH2=CH-CN` is **(a) acrylonitrile**.

---