Phosphorous halides

Presentation on phosphorous halides.

1. Phosphorous Halides By : Sanekh Das

2. Phosphorus combines with all the halogens forming phosphorus halides which are all covalent compounds. This is known as phosphorous halides. Phosphorous Chlorides are the most improtant . What are phosphorous halides?

3. Phosphorous Trichloride . Phosphorous Pentachloride . Classification of Phosphorus C hlorides.

4. Phosphorous Trichloride . Phosphorous trichloride is a chemical compound of phosphorus and chlorine, having chemical formula PCl 3 . It has a trigonal pyramidal shape. It is the most important of the two phosphorus chlorides.

5. PCl 3 is prepared by heating white phosphorus in a current of dry chlorine. P 4 + 6Cl 2 → 4PCl 3 By the action of thionyl Chloride with white phosphorous. P 4 + 8SOCl 2 → 4PCl 3 + 4SO 2 + 2S 2 Cl 2 Preparation :

6. Chemical Properties Physical Properties Properties.

7. It is a colourless oily liquid and hydrolysis in the presence of mositure . PCl 3 + 3 H 2 O → 3HCl + H 3 PO 3 On reaction with compounds containing hydroxyl (OH) groups, such as acids & alcohols. PCl 3 + 3CH 3 COOH → 3CH 3 COCl + H 3 PO 3 PCl 3 + 3C 2 H 5 OH → 3 C 2 H 5 Cl + H 3 PO 3 It has a pyramidal shape. Chemical Properties.

8. Colourless low boiling liquid It fumes in moist air. It has pungent odour . Physical Proerties .

9. PCl 3 is also used directly as a reagent in organic synthesis. It is used to convert primary and secondary alcohols into alkyl chlorides, or carboxylic acids into acyl chlorides, although thionyl chloride generally gives better yields than PCl 3 . Uses of PCl 3 :

10. Structure of PCl 3 : PCl 3 molecule has a trigonal pyramidal shape , which arises from sp 3 hybridisation of phosphorus atom. One of the tetrahedral positions is occupied by a lone pair of electrons.

11. Phosphorus pentachloride is the chemical compound with the formula PCl 5. It is mainly used as a chlorinating reagent. Phosphorous Pentachloride

12. It is usually prepared by the action of dry chlorine on phosphorus trichloride . PCl 3 + Cl 2 → PCl 5 It can also be prepared by the action of SO 2 Cl 2 on phosphorous. P 4 +10SO 2 Cl 2 → 4PCl 5 + 10SO 2 Preperation :

13. Chemical Properties. Physical Properties. Properties :

14. Phosphorus pentachloride dissociates on heating into phosphorus trichloride and chlorine. PCl 5 → PCl 3 + Cl 2 Depending upon the quantity of water on hydrolysis it is converted into the following ; Insufficient water : PCl 5 + H 2 O → POCl 3 + 2HCl Excess of water : PCl 5 + 3H 2 O → H 3 PO 4 + 3HCl Chemical Properties.

15. It is a colourless , water and moisture sensitive solid. It is a yellowish white crystalline solid. It sublimes on heating at 473K and melts at 318K under pressure. Physical Properties.

16. Used in the synthesis of some organic compounds. Eg : C 2 H 5 Cl, CH 3 COCl. Uses of PCl 5 :

17. PCl 5 molecule has trigonal bi-pyramidal shape in vapour state which arises from sp₃d hybridisation of phosphorus atom. Structure of PCl 5 :

18. Review Exercise :