Polyhalogen Compounds

This is the most factual topic in the chapter. Learn one use and one concern for each compound.

Compound	Uses	Concern
Dichloromethane, $C H_{2} C l_{2}$	Solvent, paint remover, aerosol propellant, metal cleaning	Harms the central nervous system
Chloroform, $C H C l_{3}$	Solvent for fats and resins, once an anaesthetic	Forms phosgene, $C O C l_{2}$
Iodoform, $C H I_{3}$	Once an antiseptic	Bad smell, so replaced
Carbon tetrachloride, $C C l_{4}$	Refrigerant feedstock, solvent	Depletes ozone
Freons, such as $C C l_{2} F_{2}$	Refrigerants, aerosol propellants	Deplete ozone
DDT	Insecticide against malaria mosquitoes	Persists, stored in fat, banned in the USA in 1973

2 C H C l_{3} + O_{2} \frac{l i g h t}{} \to 2 C O C l_{2} + 2 H C l

Freons

Freons are chlorofluorocarbons. Freon-12 is $C C l_{2} F_{2}$ , made from $C C l_{4}$ by Swarts fluorination. In equation form: $3 C C l_{4} + 2 S b F_{3} \to 3 C C l_{2} F_{2} + 2 S b C l_{3}$ . They are very stable, so they drift up to the stratosphere, where ultraviolet light breaks them and releases chlorine atoms.

Why a little CFC does a lot of damage in the stratosphere.

Other names that have been asked

Gammaxene is $C_{6} H_{6} C l_{6}$ , chloropicrin is $C C l_{3} N O_{2}$ , and chloral is $C C l_{3} C H O$ . DDT is made from chlorobenzene and chloral with concentrated $H_{2} S O_{4}$ .

In 60 seconds

Freons

Other names that have been asked