A:tetracyanomethane B:carbondioxide
C:Benzene C:1,3-But-di-ene
Ratio of `sigma and pi` bonds is in order:

Options

A. `A=BltCltD`
B. `A=BltDltC`
C. `A=B=C=D`
D. `CltCltAltB`

Answer

To determine the ratio of sigma (σ) and pi (π) bonds in the given molecules (A: tetracyanomethane, B: carbon dioxide, C: benzene, D: 1,3-butadiene), we will analyze each molecule step by step.

### Step 1: Analyze Tetracyanomethane (A)
- **Structure**: Tetracyanomethane has a central carbon atom bonded to four cyanide (−C≡N) groups.
- **Bonds**: Each cyanide group has a triple bond (1 σ bond and 2 π bonds).
- **Calculating Bonds**:
- 4 cyanide groups contribute:
- 4 σ bonds (1 from each triple bond)
- 8 π bonds (2 from each triple bond)
- **Total Bonds in A**:
- Total σ bonds = 4 (from CN bonds)
- Total π bonds = 8 (from CN bonds)
- **Ratio**:
\[ \text{Ratio (A)} = \frac{4 \text{ σ bonds}}{8 \text{ π bonds}} = \frac{4}{8} = 1 \]

### Step 2: Analyze Carbon Dioxide (B)
- **Structure**: Carbon dioxide has a linear structure with the formula CO₂.
- **Bonds**: Each carbon-oxygen bond is a double bond.
- **Calculating Bonds**:
- 2 double bonds contribute:
- 2 σ bonds (1 from each double bond)
- 2 π bonds (1 from each double bond)
- **Total Bonds in B**:
- Total σ bonds = 2
- Total π bonds = 2
- **Ratio**:
\[ \text{Ratio (B)} = \frac{2 \text{ σ bonds}}{2 \text{ π bonds}} = \frac{2}{2} = 1 \]

### Step 3: Analyze Benzene (C)
- **Structure**: Benzene has a cyclic structure with alternating double bonds (C₆H₆).
- **Bonds**: Each carbon-carbon bond is a single bond or part of a double bond.
- **Calculating Bonds**:
- 6 C-H bonds contribute 6 σ bonds.
- 3 double bonds contribute:
- 3 σ bonds (1 from each double bond)
- 3 π bonds (1 from each double bond)
- **Total Bonds in C**:
- Total σ bonds = 6 (C-H) + 3 (C-C) = 9
- Total π bonds = 3
- **Ratio**:
\[ \text{Ratio (C)} = \frac{9 \text{ σ bonds}}{3 \text{ π bonds}} = \frac{9}{3} = 3 \]

### Step 4: Analyze 1,3-Butadiene (D)
- **Structure**: 1,3-butadiene has a linear structure with two double bonds (C₄H₆).
- **Bonds**: Each double bond contributes to both σ and π bonds.
- **Calculating Bonds**:
- 2 double bonds contribute:
- 2 σ bonds (1 from each double bond)
- 2 π bonds (1 from each double bond)
- 2 additional σ bonds from the single bonds between the carbon atoms.
- **Total Bonds in D**:
- Total σ bonds = 4 (2 from double bonds + 2 from single bonds)
- Total π bonds = 2
- **Ratio**:
\[ \text{Ratio (D)} = \frac{4 \text{ σ bonds}}{2 \text{ π bonds}} = \frac{4}{2} = 2 \]

### Final Ratios Summary
- A: 1
- B: 1
- C: 3
- D: 2

### Order of Ratios
The order of the ratio of σ to π bonds is:
- A = B < D < C

### Final Answer
The correct order of the ratio of sigma to pi bonds is:
**A = B < D < C**