The CNC bond angle in `CH_3NCS` is:

Options

A. `lt 109^@28'`
B. `lt 120^@`
C. `gt 120^@`
D. `112^@`

Answer

To determine the CNC bond angle in the compound CH₃NCS, we can follow these steps:

### Step 1: Draw the Lewis Structure of CH₃NCS
- Start by identifying the atoms in the molecule: carbon (C), nitrogen (N), and sulfur (S).
- The structure consists of a carbon atom bonded to three hydrogen atoms (CH₃) and to a nitrogen atom (N). The nitrogen is then bonded to a carbon atom (C) which is double bonded to a sulfur atom (S).
- The Lewis structure can be represented as follows:
```
H
|
H--C--N=C=S
|
H
```

### Step 2: Determine the Hybridization of the Atoms
- The central nitrogen atom (N) is bonded to two atoms (C and C), which suggests that it is sp² hybridized.
- The carbon atom bonded to nitrogen (C) is also sp² hybridized because it is involved in a double bond with sulfur (S).

### Step 3: Analyze the Geometry Around the Nitrogen Atom
- The sp² hybridization indicates that the geometry around the nitrogen atom is trigonal planar.
- In a trigonal planar arrangement, the bond angles are typically around 120 degrees.

### Step 4: Consider the Influence of Lone Pairs
- The nitrogen atom has one lone pair of electrons. This lone pair will slightly compress the bond angles between the bonded atoms (C and C).
- Therefore, the CNC bond angle will be slightly less than 120 degrees due to the repulsion from the lone pair.

### Step 5: Conclusion
- Based on the analysis, the CNC bond angle in CH₃NCS is less than 120 degrees.

### Final Answer
The CNC bond angle in CH₃NCS is less than 120 degrees.

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