Chloromethane

Description

Methyl chloride is a colorless, flammable gas with a faintly sweet, nonirritating odor at room temperature. It is shipped as a transparent liquid under its vapor pressure of about 59 psig at 70°F (407 kPa at 21.1℃）.
Methyl chloride burns feebly in air, but forms mixtures with air that can be explosive within its flammability range.
Dry methyl chloride is very stable at normal temperatures and in contact with air. In the presence of moisture, it hydrolyzes slowly, which results in the formation of corrosive hydrochloric acid. At temperatures above 700°F (371℃）, methyl chloride may decompose into toxic end-products (hydrochloric acid, phosgene, chlorine, and carbon monoxide). It is slightly soluble in water and very soluble in alcohol, mineral oils, chloroform, and most organic liquids.

Description

Chloromethane, frequently called methyl chloride, is a colorless, toxic gas. It has been known since the early 19th century.
In 1835, prominent French chemists Jean-Baptiste Dumas of the école Polytechnique and Eugène Péligot of the Institut National Agronomique (both in Paris) teamed up to devise the first synthesis of chloromethane. They heated methanol and sodium chloride in the presence of sulfuric acid to produce the gas. Their synthesis was the forerunner of the primary modern manufacturing method, which uses hydrogen chloride in place of NaCl and H2SO4.
Chloromethane is found sparsely in nature. It is usually produced by the enzyme methyl chloride tranferase, which is present in wood-rotting fungi and salt marsh plants. As of 2020, chloromethane was the only organochlorine compound to have been detected in space, by both the Atacama Large Millimeter/submillimeter Array telescope in Chile and the Rosetta spacecraft.
Chloromethane was once widely used as a refrigerant1, but it has long since been replaced by substances that are less toxic and less harmful to the ozone layer in Earth’s atmosphere. Currently, it is used in industry as a reagent in chemical production, an extractant for oils and resins, a propellant in foam production, and a solvent in rubber manufacture and petroleum refining.
1. As a refrigerant, chloromethane was called Freon-40.

Chemical properties

Methyl chloride,CH3CI, is a flammable, narcotic,colorless compressed gas or liquid with a faintly sweet odor.Slightly soluble in water and soluble in alcohol this gas boils at -23.7℃ and freezes at -97.6℃ and is used as a refrigerant, catalyst carrier, and methylating agent. Also known as chloromethane.

Chemical properties

Methyl chloride is a colorless gas with a faint, sweet odor which is not noticeable at dangerous concentrations. The odor threshold is 10 ppm. Shipped as a liquefied compressed gas.

Physical properties

Colorless, liquefied compressed gas, with a sweet, ethereal odor. Volatile flammable gas. An experimentally determined odor threshold concentration of >100 ppm_v was reported by Leonardos et al. (1969).

The Uses of Chloromethane

manufacture of silicones, tetramethyleads. Solvent catalyst for butyl rubber. Has been used as a refrigerant.

The Uses of Chloromethane

Methyl chloride is used as a refrigerant,as a local anesthetic, as a blowing agentfor polystyrene foams, and as a methylat ing agent in the synthesis of a number ofchemicals of commercial application.

The Uses of Chloromethane

Nearly equal amounts of methyl chloride are used in making these rubbers and the other principal user, production of tetramethyllead.

Definition

ChEBI: A one-carbon compound that is methane in which one of the hydrogens is replaced by a chloro group.

Production Methods

Methyl chloride has been used in rubber adhesives and other rubber solutions; in the pharmaceutical industry; as a paint and varnish remover; in solvent degreasing; in aerosol 2 JON B. REID AND CUSTODIO V. MUIANGA formulations; in food and drug processing; in the plastics industry; in hair sprays, insecticides, and spray paints; as a cosolvent or vapor pressure depressant; as a blowing agent for flexible polyurethane foams; as a cleaning solvent for printed circuit boards; as a stripper solvent for photoresists; as a solvent for cellulose acetate fiber; in plastic film; in protective coatings; in chemical processing; as a carrier solvent for herbicides and insecticides; to extract heatsensitive, naturally occurring substances such as cocoa, edible fats, spices, and beer hops; for decaffeinating coffee; as a refrigerant; in oil dewaxing; as a dye and perfume intermediate; in the textile industry; as a postharvest fumigant for strawberries; as a grain fumigant; for degreening citrus fruits; as an industrial solvent; in low-temperature extraction; as a solvent for oil, fats, bitumen, esters, resins, and rubber; in coating photographic films; as a food additive; in synthetic fibers and leather coatings; as a spotting agent; and in organic synthesis.

Production Methods

Methyl chloride is also commercially produced by reaction of HCl on methanol in the presence of zinc chloride. Methyl chloride is mainly used in the production of silicone resins and rubbers. Silicon is reacted with an excess of methyl chloride at 300 °C in the presence of a copper catalyst. The product includes mono-, di-, and trichloromethyl silanes. Hydrolysis of the chloro groups converts them into the corresponding hydroxymethylsilanes.

General Description

A colorless gas with a faint sweet odor. Shipped as a liquid under its vapor pressure. A leak may either be liquid or vapor. Contact with the liquid may cause frostbite by evaporative cooling. Easily ignited. Vapors heavier than air. Can asphyxiate by the displacement of air. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. Used to make other chemicals and as a herbicide.

Air & Water Reactions

Highly flammable.

Reactivity Profile

METHYL CHLORIDE can react vigorously with oxidizing agents. May react explosively with sodium, potassium, sodium-potassium alloy, magnesium, zinc. Reacts with aluminum powder in the presence of catalytic amounts of aluminum chloride to form pyrophoric trimethylaluminum. When heated to decomposition, METHYL CHLORIDE emits highly toxic fumes of chlorine [Bretherick, 5th ed., 1995, p. 176].

Hazard

Flammable, dangerous fire risk, explosive limits in air 10.7–17%. Narcotic. Psychic effects. Central nervous system impairment; liver, kidney and testicular damage, and teratogenic effects. Questionable carcinogen.

Health Hazard

Inhalation causes nausea, vomiting, weakness, headache, emotional disturbances; high concentrations cause mental confusion, eye disturbances, muscular tremors, cyanosis, convulsions. Contact of liquid with skin may cause frostbite.

Health Hazard

Inhalation of methyl chloride can produceheadache, dizziness, drowsiness, nausea,vomiting, convulsions, coma, and respiratoryfailure. It is narcotic at high concentrations.Repeated exposures can produce liver and Methyl chloride caused adverse reproduc tive effects in test animals. These includeembryo toxicity, fetal death, developmentalabnormalities, and paternal effects in rats andmice. It tested positive to the histidine rever sion–Ames test for mutagenicity. The car cinogenic properties of this compound havenot been established. The evidence in ani mals and humans is inadequate.

Fire Hazard

Flammable gas, burns with a smoky flame; autoignition temperature 632°C (1170°F). Methyl chloride forms explosive mixtures with air within the range 7.6–19.0% by volume in air. It reacts explosively with alkali metals, potassium, sodium, or lithium; sodium–potassium alloy; and with magnesium, aluminum, or zinc in powder form.

Materials Uses

Dry methyl chloride may be contained in such common metals as steel, iron, copper, and bronze, but it has a corrosive action on zinc, aluminum, die castings, and possibly magnesium alloys. Methyl chloride must not be used with aluminum, since in the presence of moisture it forms spontaneously flammable methyl aluminum compounds upon contact with that metal. No reaction occurs, however, with the drying agent, activated alumina.
Gaskets made of natural rubber and many neoprene compositions should be avoided because methyl chloride dissolves many organic materials. Pressed fiber gaskets, including those made of asbestos may be used with methyl chloride. Polyvinyl alcohol is unaffected by methyl chloride, and its use is also recommended. Medium- soft metal gaskets may be used for applications where alternating stresses such as those resulting from large temperature changes do not lead to "ironing out" and consequent leakage.

Safety Profile

Suspected carcinogen. Very mildly toxic by inhalation. An experimental teratogen. Other experimental reproductive effects. Human mutation data reported. Human systemic effects by inhalation: convulsions, nausea or vomiting, and unspecified effects on the eye. Methyl chloride has slight irritant properties and may be inhaled without noticeable discomfort. It has some narcotic action, but this effect is weaker than that of chloroform. Acute poisoning, characterized by the narcotic effect, is rare in industry. In exposures to high concentrations, dizziness, drowsiness, incoordination, confusion, nausea and vomiting, abdominal pains, hiccoughs, diplopia, and dimness of vision are followed by delirium, convulsions, and coma. Death may be immediate; however, if the exposure is not fatal, recovery is usually slow. Degenerative changes in the central nervous system are not uncommon. The liver, hdneys, and bone marrow may be affected, with resulting acute nephritis and anemia. Death resulting from degenerative changes in the heart, liver, and especially the kidneys may occur several days after exposure. Repeated exposure to low concentrations causes damage to the central nervous system and, less frequently, to the liver, hdneys, bone marrow, and cardiovascular system. Hemorrhages into the lungs, intestinal tract, and dura have been reported. Sprayed on the skin, chloromethane produces anesthesia through freezing of the tissues as it evaporates. Flammable gas. Very dangerous fire hazard when exposed to heat, flame, or powerful oxidizers. Moderate explosion hazard when exposed to flame and sparks. Explodes on contact with interhalogens (e.g., bromine trifluoride, bromine pentafluoride), magnesium and alloys, potassium and alloys, sodium and alloys, zinc. Potentially explosive reaction with aluminum when heated to 152' in a sealed container. Mxtures with aluminum chloride + ethylene react exothermically and then explode when pressurized to above 30 bar. May ignite on contact with aluminum chloride or powdered aluminum. To fight fire, stop flow of gas and use CO2, dry chemical, or water spray. When heated to decomposition it emits highly toxic fumes of Cl-. See also CHLORINATED HYDROCARBONS, ALIPHATIC.

Potential Exposure

Methyl chloride is used as a methylating and chlorinating agent in organic chemistry; Used in production of silicones and tetramethyl lead. In petroleum refineries it is used as an extractant for greases, oils, and resins. Methyl chloride is also used as a solvent in the synthetic rubber industry; as a refrigerant; and as a propellant in polystyrene foam production. In the past it has been used as a local anesthetic (freezing). It is an intermediate in drug manufacture.

Physiological effects

Methyl chloride is toxic, and areas where it is handled must be adequately ventilated. It is particularly dangerous in that it has no pronounced odor to serve as a warning.
It acts as an anesthetic about one-fourth as potent as chloroform, and also acts as a narcotic. Inhalation must be avoided. Mild cases of methyl chloride poisoning usually suffer from ataxia, lightheadedness, confusion, tremors, nausea and vomiting, and frequently from anorexia after a latent period of one-half to several hours. Hiccough and constricting pain in the neck may also be experienced. Visual disturbances such as double vision are frequently reported.
Severe nonfatal poisonings are also characterized by a latent period of several hours between exposure and the onset of the first signs or symptoms. This varies with individual susceptibility and the intensity of exposure. Exposure to high concentrations of several hundred ppm or more leads successively to dizziness, headache, vertigo, loss of coordination, nausea and vomiting, abdominal pain, tremors, extreme nervousness, mental confusion, convulsion, unconsciousness, coma, and eventually death. Rapid pulse, lowered blood pressure, elevated body temperature, and rapid respiration are among additional signs of exposure that may be present. Some victims may show signs of liver injury associated with jaundice and porphyrinuria, and renal disturbances characterized by albuminuria and oliguria, which may pass into anuria. Complete recovery from severe methyl chloride poisoning may take weeks or months.
Fatal methyl chloride poisoning can have symptoms similar to those of severe nonfatal poisoning. Apparent recovery from what seems a mild exposure through inhalation may be followed by serious, prolonged or even fatal aftereffects within a few days or weeks as a result of cerebral and pulmonary edema and circulatory failure. Repeated exposures are dangerous because methyl chloride is eliminated slowly from the body, where it is converted into hydrochloric acid and methyl alcohol (wood alcohol). ACGIH recommends a Threshold Limit Value-Time-Weighted Average (TLV-TWA) of 50 ppm (103 mg/m3 ) for methyl chloride.
The TLV-TWA is the time-weighted average concentration for a normal 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed, day after day, without adverse effect. ACGIH also recommends a Threshold Limit Value-Short Term Exposure Limit (TLV-STEL) of 100 ppm (207 mg/m3 ) for methyl chloride. The TLV-STEL is the 15-minute TWA exposure that should not be exceeded at any time during a workday even if the 8-hour TWA is within the TLV-TWA. Exposures above the TLV-TWA up to the STEL should not be longer than 15 minutes and should not occur more than 4 times per day. There should be at least 60 minutes between successive exposures in this range .
OSHA lists an 8-hour Time-Weighted Average- Permissible Exposure Limit (TWA-PEL) of 100 ppm for methyl chloride. TWA-PEL is the exposure limit that shall not be exceeded by the 8-hour TWA in any 8-hour work shift of a 40-hour workweek. In addition, OSHA lists an acceptable ceiling concentration of 200 ppm for methyl chloride. The acceptable ceiling concentration is the exposure limit that shall not be exceeded at any time during an 8-hour shift. Methyl chloride has an exception in that it has an acceptable maximum peak above the acceptable ceiling concentration of 300 ppm for an 8-hour shift as long as the maximum duration is only once for 5 minutes in any hour.
Contact of methyl chloride liquid (or vapor in a concentrated stream) with the skin or the eyes must also be avoided, for such contact can result in a condition resembling frostbite of the tissues.

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit. If frostbite has occurred, seek medical attention immediately; do NOT rub the affected areas or flush them with water. In order to prevent further tissue damage, do NOT attempt to remove frozen clothing from frostbitten areas. If frostbite has NOT occurred, immediately and thoroughly wash contaminated skin with soap and water. Medical observation is recommended for 2448 h after breathing overexposure, as pulmonary edema may be delayed. As first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a corticosteroid spray.

Carcinogenicity

Methyl chloride was mutagenic to bacteria and genotoxic in a number of mammalian cell systems in vitro.14 It gave positive results in the dominant lethal test in rats in vivo.
NIOSH recommends that methyl chloride be considered a potential occupational teratogen and carcinogen.
The IARC states that there is inadequate evidence for the carcinogenicity of methyl chloride to experimental animals and humans.

Source

Drinking water standard: No MCLGs or MCLs have been proposed although methyl chloride has been listed for regulation (U.S. EPA, 1996). In addition, 100 μg/L was recommended (U.S. EPA, 2000).

Environmental Fate

Biological. Enzymatic degradation of methyl chloride yielded formaldehyde (Vogel et al., 1987).
Photolytic. Reported photooxidation products via OH radicals include formyl chloride, carbon monoxide, hydrogen chloride, and phosgene (Spence et al., 1976). In the presence of water, formyl chloride hydrolyzes to HCl and carbon monoxide, whereas phosgene hydrolyzes to hydrogen chloride and carbon monoxide (Morrison and Boyd, 1971).
Methyl chloride reacts with OH radicals in the atmosphere at a rate of 8.5 x 10^-14 cm³/sec with a lifetime of 135 d (Cox et al., 1976).
Chemical/Physical. The estimated hydrolysis half-life at 25 °C and pH 7 is 0.93 yr (Mabey and Mill, 1978).
The evaporation half-life of methyl chloride (1 mg/L) from water at 25 °C using a shallow-pitch propeller stirrer at 200 rpm at an average depth of 6.5 cm was 27.6 min (Dilling, 1977).

Solubility in water

Miscible with chloroform, ether, glacial acetic acid (U.S. EPA, 1985), and other chlorinated hydrocarbons including carbon tetrachloride.

storage

All personnel handling methyl chloride cylinders should be fully informed about the dangers that can arise from improper handling of methyl chloride. The cylinder and system should be grounded before use. Before introducing methyl chloride into any apparatus or equipment, it should be tested for leaks, all leaks repaired, and the apparatus thoroughly dried. Only nonsparking tools should be used with methyl chloride. Chemical safety goggles and/or a full-face shield should be used when handling liquid methyl chloride.

Shipping

UN1063 Methyl chloride, or Refrigerant gas R 40, Hazard Class: 2.1; Labels: 2.1-Flammable gas. Cylinders must be transported in a secure upright position, in a well-ventilated 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

Purification Methods

Bubble methyl chloride through a sintered-glass disc dipped into conc H2SO4, then wash it with water, condense it at low temperature and fractionally distil it. It has been distilled from AlCl3 at -80o. Alternatively, pass it through towers containing AlCl3, soda-lime and P2O5, then condense and fractionally distil it. Store it as a gas. [Beilstein 1 IV 28.]

Incompatibilities

Violent reaction with chemically active metals, such as potassium, powdered aluminum; zinc, and magnesium. Reaction with aluminum trichloride, ethylene. Reacts with water (hydrolyzes) to form hydrochloric acid. Attacks many metals in the presence of moisture

Waste Disposal

Return refillable compressed gas cylinders to supplier. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Controlled incineration with adequate scrubbing and ash disposal facilities

GRADES AVAILABLE

Methyl chloride is available for commercial and industrial use in various grades having much the same component proportions from one producer to another. Purities generally range from a minimum of99.5 mole percent.