In Zeigler-Natta polymerisation of ethylene, the active species is

Options

A. `AICI_(3)`
B. `TiCI_(4)`
C. `Et_(3)AI`
D. `Ti^(3+)`

Answer

**Step-by-Step Solution:**

1. **Understanding Ziegler-Natta Polymerization**:
Ziegler-Natta polymerization is a method used to synthesize polymers from alkenes, particularly ethylene. It involves the use of a specific type of catalyst known as the Ziegler-Natta catalyst.

2. **Components of Ziegler-Natta Catalyst**:
The Ziegler-Natta catalyst consists of two main components:
- A transition metal compound (often from group 4 of the periodic table, such as titanium, zirconium, or hafnium).
- An organo-aluminum compound, which contains a bond between aluminum and carbon.

3. **Examples of Ziegler-Natta Catalysts**:
Common examples of Ziegler-Natta catalysts include:
- Titanium tetrachloride (TiCl4) combined with triethylaluminum (Et3Al).
- Titanium trichloride (TiCl3) combined with diethylaluminum chloride (AlEt2Cl).

4. **Reaction Mechanism**:
In the presence of the Ziegler-Natta catalyst, ethylene (C2H4) molecules undergo polymerization. The catalyst facilitates the reaction by providing an active site for the polymerization process.

5. **Formation of Active Species**:
During the polymerization process, the organo-aluminum compound can reduce the titanium compound. For example, triethylaluminum can reduce TiCl4 to TiCl3. The titanium in the TiCl3 state has a +3 oxidation state (Ti^3+), which is the active species in this polymerization process.

6. **Conclusion**:
Therefore, the active species in the Ziegler-Natta polymerization of ethylene is titanium in the +3 oxidation state, represented as Ti^3+.

**Final Answer**: The active species in Ziegler-Natta polymerization of ethylene is Ti^3+.

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