Phosphorus Trichloride ($PCl_3$): Structure, Preparation & Properties
Phosphorus Trichloride is a colorless oily liquid that fumes in moist air. It is a crucial reagent in organic synthesis for converting alcohols to alkyl chlorides.
1. Preparation of $PCl_3$
It is generally prepared by passing dry chlorine gas over heated white phosphorus.
Caution
It fumes in moist air due to hydrolysis, producing $\text{HCl}$ gas:
$PCl_3 + 3H_2O \rightarrow H_3PO_3 + 3HCl$
Figure: Comprehensive Reaction Chart of Phosphorus Trichloride ($PCl_3$)
2. Chemical Properties & Reactions
$PCl_3$ acts as a source of chlorine atoms in organic reactions, replacing hydroxyl groups with chlorine.
Organic Transformations
- Reaction with Alcohols: Forms alkyl chlorides.
$3CH_3COOH + PCl_3 \rightarrow 3CH_3COCl + H_3PO_3$ - Reaction with Acids: Forms acid chlorides.
$3C_2H_5OH + PCl_3 \rightarrow 3C_2H_5Cl + H_3PO_3$
Structure (Pyramidal)
The central phosphorus atom is $sp^3$ hybridized with one lone pair, giving it a pyramidal shape (similar to Ammonia).
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