Difluorochloromethane

Description

Chlorodifluoromethane (ClCF2H), also known as Freon 22, is a highly halogenated gas that can be used as a refrigerant or propellant. But it is a threat to the ozone layer, and under the Montreal Protocol it has been nearly phased out in the United States and other developed countries.
The phaseout restricted the utility of ClCF2H to the manufacture of fluorinated compounds (e.g., tetrafluoroethylene) until this year, when Xingang Zhang and colleagues at the Shanghai Institute of Organic Chemistry discovered that it can be used as a difluoromethylating agent. They found that, by using a transition-metal catalyst, the ClCF2?group can be coupled with aromatic boronic acids to form difluoromethyl-substituted aromatics.
In one example, the authors replaced the nitrile group in the herbicide cyhalofop-butyl with a ClCF2?group by converting the nitrile to a boronate ester and then treating the boronate with ClCF2H, the Pd2(dba)2* complex, and the Xantphos** ligand under relatively mild conditions (110 °C for 48 h). The yield of the difluoromethylation step was 90%, on the high end of the reactions given in this report.
The authors are currently attempting to discover the detailed mechanism of the difluoromethylation reaction and to reduce the amounts of reagents and catalyst required.
* dba = dibenzylideneacetone
** Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene

Description

Chlorodifluoromethane is a nonflammable,colorless, nearly odorless gas. Molecular weight =86.47;Specific gravity (H2O:1) 5=1.21; Boiling point =-40.5℃;Freezing/Melting point =-146℃; Vapor pressure =9.4atm at 20℃; Autoignition temperature=632℃. HazardIdentification (based on NFPA 704 M Rating System):Health 2, Flammability 0, Reactivity 0. Soluble in water;solubility =0.3% at 25℃

Chemical properties

colourless gas

Chemical properties

Chlorodifluoromethane is a nonflammable, colorless, nearly odorless gas.

The Uses of Difluorochloromethane

Aerosol propellant; refrigerant; lowtemperature solvent

The Uses of Difluorochloromethane

Refrigerant, low-temperature solvent, fluorocarbon resins, especially tetrafluoroethylene polymers.

Definition

ChEBI: Chlorodifluoromethane is a hydrochlorofluorocarbon.

General Description

Difluorochloromethane is a colorless gas with an ethereal odor. Difluorochloromethane is shipped as a liquefied gas under its own vapor pressure. Difluorochloromethane is noncombustible. Difluorochloromethane can asphyxiate by the displacement of air. Contact with the liquid can cause frostbite. Toxic gases can be produced in fires involving Difluorochloromethane. Exposure of the container to prolonged heat or fire may cause Difluorochloromethane to rupture violently and rocket.

Air & Water Reactions

The liquefied gas poured into water can be violently explosive. This is due to the phase transition from superheated liquid to vapor.

Reactivity Profile

Difluorochloromethane is incompatible with the following: Alkalis, alkaline earth metals (e.g., powdered aluminum, sodium, potassium, zinc) .

Hazard

Asphyxiant. Central nervous system impairment, cardiac sensitization. Questionable carcinogen.

Health Hazard

Inhalation at greater than 10% concentration in air may cause narcosis. Liquid may cause frostbite.

Fire Hazard

Special Hazards of Combustion Products: Decomposition gases are toxic and irritating.

Safety Profile

Mddly toxic by inhalation. Experimental reproductive effects. Mutation data reported. An asphpant in hgh concentrations. At elevated pressures, 50% mixtures with air are combustible although ignition is dfficult. When heated to decomposition it emits toxic fumes of Fand Cl-. See also CHLORINATED HYDROCARBONS, ALIPHATIC; and FLUORIDES.

Potential Exposure

Chlorodifluoromethane is used as an aerosol propellant, refrigerant, and low-temperature solvent. It is used in the synthesis of polytetrafluoroethylene (PTFE).

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.If frostbite has occurred, seek medical attention immediately; do NOT rub the affected areas or flush them withwater. In order to prevent further tissue damage, do NOTattempt to remove frozen clothing from frostbitten areas. Iffrostbite has NOT occurred, immediately and thoroughlywash contaminated skin with soap and water.

Carcinogenicity

In one study, an oral dose of 300mg of HCFC 22/kg of body weight was given to 36 male and 36 female rats 5 days/week for 52 weeks. The rats were held for 125 weeks compared to controls. There was no evidence of any treatment related increase in tumors. In an inhalation study 60 male and 60 female rats were exposed by inhalation to levels of
5000 ppm of HCFC 22. The exposures were 4 h/day, 5 days/week for 104 weeks (rats) or 78 weeks (mice).

storage

Nonflammable gas. Color Code—Green: Generalstorage may be used. Prior to working with chlorodifluoromethane you should be trained on its proper handling andstorage. Store in tightly closed containers in a cool, wellventilated area. Sources of ignition, such as smoking andopen flames, are prohibited where this chemical is used,handled, or stored in a manner that could create a potentialfire or explosion hazard. Procedures for the handling, use,and storage of cylinders should be in compliance withOSHA 1910.101 and 1910.169, as with the recommendations of the Compressed Gas Association. A regulated,marked area should be established where this chemical ishandled, used, or stored in compliance with OSHAStandard 1910.1045.

Shipping

UN1018 Chlorodifluoromethane, Hazard Class: 2.2; Labels: 2.2-Non-flammable compressed gas. Cylinders must be transported in a secure upright position, in a wellventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner.

Incompatibilities

The liquefied gas poured into water can be violently explosive. This is due to the phase transition from superheated liquid to vapor. Chlorodifluoromethane reacts violently with alkalies and alkaline earth metals; powdered aluminum; sodium, potassium, and zinc; causing fire and explosion hazard. Moisture and rust cause slow decomposition, forming toxic gases. Attacks some plastics, rubber, and coatings. Decomposes in heat forming fumes of chlorine, hydrogen chloride, HF, and phosgene. Attacks magnesium and its alloys.

Waste Disposal

Return refillable compressed gas cylinders to supplier. Return to vendor or send to licensed waste disposal company.