Question

Give the properties of the following:

PCl₃

Answer 1

1. The colourless, mobile liquid phosphorus trichloride has a strong odour and a boiling point of 349 K.

2. It odours in damp air because it reacts easily with water.

\[\ce{PCl3 + 3H2O -> H3PO4 + 3HCl}\]

3. It produces chlorosulphonic acid when it interacts with concentrated H₂SO₄.

\[\ce{H2SO4 + PCl3 -> \underset{acid}{\underset{Chlorosulphonic}{Cl * SO2 * OH}} + POCl + HCl}\]

POCl further reacts with H₂SO₄ and forms P₂O₅.

\[\ce{2H2SO4 + 2POCl -> P2O5 + 2SO2 + 2HCl + H2O}\]

4. It reacts with organic molecules that have hydroxyl (-OH) groups, substituting a chlorine atom for the hydroxyl group.

For example:

\[\ce{\underset{Ethyl alcohol}{3C2H5OH} + PCl3 -> \underset{Ethyl chloride}{3C2H5Cl} + \underset{Phosphorus acid}{H3PO3}}\]

\[\ce{\underset{Acetic acid}{3CH3COOH} + PCl3 -> \underset{Acetyl chloride}{3CH3COCl} + \underset{Phosphorus acid}{H3PO3}}\]

5. It reacts with chlorine to form phosphorus pentachloride.

\[\ce{PCl3 + Cl2 -> PCl5}\]

6. It reacts with oxygen to give phosphorus oxytrichloride.

\[\ce{2PCl3 + O2 -> 2POCl3}\]