Halogenated solvents

Dr. Dmitri Kopeliovich

Halogenated solvent is an organic solvent, molecules of which contain halogenic atoms: chlorine (Cl), fluorine (F) , bromine (Br) or iodine (I).

• Chlorinated solvents
• Fluorocarbon solvents
• Brominated solvents
• Iodinated solvents
• Properties of some halogenated solvents

• The common chlorinated solvents are Trichlorethylene (ClCH-CCl₂), Perchlorethylene (tetrachlorethylene, Cl₂C-CCl₂), Methylene chloride (CH₂Cl₂), Carbon tetrachloride (CCl₄)), Chloroform (CHCl₃), 1,1,1-trichloroethane (methyl chloroform, CH₃-CCl).
  

Chlorinated solvents are the most popular halogenated solvents.

• Chlorinated solvents are used in dry cleaning, metal cleaning, degreasing, automotive aerosols, printing, paper and textile industries, paint removal, furniture industry, Thermoplastics production.

• Health effect of chlorinated solvents:
  

They may affect central nervous system, kidneys and liver, cause dermatitis and irritation of skin, eyes, upper respiratory tract and mucous membranes.
Over-exposure in poorly ventilated space may lead to depression, headache, sleepiness, unconsciousness and even death.
Some chlorinated solvents cause cancer in rats and mice at high exposure levels.
According to the National Institute for Occupatuional Safety (NIOSH), National Toxicology Program (NTP), International Agency for Research on Cancer (IARC) and American Conference of Governmental Industrial Hygienists (ACGIH):
- Trichlorethylene is a suspect carcinogen;
- Perchlorethylene is not classified as carcinogen;
- Methylene chloride is a potential carcinogen (ACGIH);
- Carbon tetrachloride is a suspect carcinogen, carcinogen Cat. 3 (ACGIH);
- Chloroform is a suspect carcinogen;
- 1,1,1-Trichloroethane is not listed as carcinogen.

• Environmental effect of chlorinated solvents:
  

Vapors of chlorinated solvent degrade in the atmosphere for a period between one week (trichloroethylene) to 5-6 months (perchlorethylene and methylene chloride).
Ozone Depletion Potential (ODP) of carbon tetrachloride and chloroform is high (more than 0.2) and their use is forbidden. ODP of trichlorethylene, perchlorethylene and methylene chloride is low and they are not regulated by the Montreal Protocol.
Spillage of chlorinated solvents to soil or water cause contamination. Methylene chloride is biodegradable. Other chlorinated solvents degrade only after reavaporation to the atmosphere.
Contributions of chlorinated solvents to global warming, acid rain production and smog formation are low.

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• Examples of fluorocarbon solvents: Dichlorofluoromethane (freon 21, CHCl₂F), Trichlorofluoromethane (Freon 11, CCl₃F), Tetrafluoromethane (Freon 14, CF₄), Difluorodichloromethane (Freon 12, CHCl₂F₂), Hydrochlorofluorocarbon (Chlorodifluoromethane, Freon 22, CHClF₂).

• Fluorocarbon solvents are widely used as refrigerants.

• Health effect of fluorocarbon solvents: The may cause heart damage, dizziness, headache, nausea.

• Environmental effect of fluorocarbon solvents: Some of fluorocarbon solvents (freon 11,freon 21) are forbidden in most countries because of their high ozone depletion potential (Montreal Protocol).

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• Examples of brominated solvents: Ethylene Dibromide (1,2-dibromoethane, BrCH₂-CH₂Br), methylene chlorobromide (bromochloromethane, CH₂BrCl), methyl bromine (bromomethane, CH₂Br).

• Brominated solvents are used as additives in leaded gasoline, soil sterilants, for manufacturing pesticides and fumigants.

• Health effect of brominated solvents: They affect liver and kidneys , cause dermatitis and irritation of skin, eyes, upper respiratory tract and mucous membranes.
  

Inhaling brominated solvents may cause dizziness, weakness, depression, headache, sleepiness.

• Environmental effect of brominated solvents: Some of brominated solvents (methylene chlorobromide, methyl bromine) are forbidden in most countries because of their high ozone depletion potential (Montreal Protocol).

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• Examples of iodinated solvents: n-butyl iodide (1-iodobutane, CH₃CH₂CH₂CH₂I), Methyl Iodide (iodomethane, CH₃I), ethyl iodide (iodoethane, C₂H₅I), n-propyl iodide (1-iodopropane, CH₃CH₂CH₂I).

• Iodinated solvents are used as intermediates for numerous chemicals, dyes, fumigants, X-ray contrast media, antiseptics, insecticides, quaternary ammonium compounds, flavors and fragrances and pharmaceuticals, in microscopy and in testing for pyridine.

• Health effect of iodinated solvents: They are suspected carcinogen and may cause irritation of skin and eyes.

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(Materials Data)

• Trichlorethylene
• Perchlorethylene
• Methylene chloride
• Carbon tetrachloride
• Chloroform
• 1,1,1-trichloroethane
• Trichlorofluoromethane
• Difluorodichloromethane
• Tetrafluoromethane
• Dichlorofluoromethane
• Hydrochlorofluorocarbon
• Ethylene Dibromide
• Methyl Iodide

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• Classification of solvents
• Hydrocarbon solvents

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