The ratio of `sigma-` bond and `pi-` bond in tetracryano ethylene is `:`

Options

A. `2:1`
B. `1:1`
C. `1:2``
D. None of these

Explanation

To determine the ratio of sigma bonds to pi bonds in tetracyanoethylene, we can follow these steps:

### Step 1: Understand the structure of tetracyanoethylene
Tetracyanoethylene consists of an ethylene (C=C) core with four cyano (C≡N) groups attached to it. The structure can be represented as:

```
N≡C
|
C=C
|
N≡C
```

### Step 2: Identify the types of bonds in the structure
- **Ethylene (C=C)**: This double bond consists of 1 sigma bond and 1 pi bond.
- **Cyano groups (C≡N)**: Each cyano group has a triple bond, which consists of 1 sigma bond and 2 pi bonds.

### Step 3: Count the number of each type of bond
1. **C=C bond (double bond)**:
- 1 sigma bond
- 1 pi bond

2. **4 Cyano groups (C≡N)**:
- Each cyano group has 1 sigma bond and 2 pi bonds.
- Total for 4 cyano groups:
- Sigma bonds: 4 (1 for each C≡N)
- Pi bonds: 8 (2 for each C≡N)

### Step 4: Calculate the total number of sigma and pi bonds
- **Total Sigma Bonds**:
- From C=C: 1
- From 4 C≡N: 4
- **Total Sigma Bonds = 1 + 4 = 5**

- **Total Pi Bonds**:
- From C=C: 1
- From 4 C≡N: 8
- **Total Pi Bonds = 1 + 8 = 9**

### Step 5: Determine the ratio of sigma bonds to pi bonds
- The ratio of sigma bonds to pi bonds is:
- Sigma bonds: 5
- Pi bonds: 9
- Ratio = 5:9

### Final Answer
The ratio of sigma bonds to pi bonds in tetracyanoethylene is **5:9**.

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