Misplaced Pages

#86913

49-455: The reaction takes place after the addition of tetrachloromethane and a base . This base is usually a primary, secondary or tertiary amine . Instead of methyl groups other alkyl or benzyl groups may be present. A possible reaction mechanism for the Atherton-Todd reaction is presented here for the example of dimethylphosphite, just like in the overview reaction: First, a tertiary amine

98-504: A = 20.3, b = 11.6, c = 19.9 (.10 nm), β = 111°. With a specific gravity greater than 1, carbon tetrachloride will be present as a dense nonaqueous phase liquid if sufficient quantities are spilt in the environment. Despite being generally inert, carbon tetrachloride can undergo various reactions. Hydrogen or an acid in the presence of an iron catalyst can reduce carbon tetrachloride to chloroform, dichloromethane, chloromethane and even methane. When its vapours are passed through

147-417: A brass bottle with an integrated hand-pump that was used to expel a jet of liquid toward the fire. As the container was unpressurized, it could easily be refilled after use. Carbon tetrachloride was suitable for liquid and electrical fires and the extinguishers were often carried on aircraft or motor vehicles. However, as early as 1920, there were reports of fatalities caused by the chemical when used to fight

196-566: A halomethane . As a solvent , it is well suited to dissolving other non-polar compounds such as fats and oils. It can also dissolve iodine . It is volatile , giving off vapors with an odor characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene odor reminiscent of dry cleaners ' shops. Solid tetrachloromethane has two polymorphs : crystalline II below −47.5 °C (225.6 K) and crystalline I above −47.5 °C. At −47.3 °C it has monoclinic crystal structure with space group C2/c and lattice constants

245-410: A "pleasant taste". Carbon tetrachloride for anaesthetic use was made by the chlorination of carbon disulfide . It was used on at least 50 patients, of which most were women in labour. During anaesthesia, carbon tetrachloride has caused such violent muscular contractions and negative effects on the heart in some patients that it had to be replaced with chloroform or ether. Such use was experimental and

294-521: A capsule of chloroform". Because of the higher amount of chlorine atoms (compared to chloroform) in its molecule, carbon tetrachloride has a stronger anaesthetic effect than chloroform and required a smaller amount. Its anaesthetic action was likened to ether , rather than the related chloroform. It is less volatile than chloroform, therefore it was more difficult to apply and needed warm water to evaporate. Its smell has been described as "fruity", quince-like and "more pleasant than chloroform", and had

343-544: A considerable effort has been extended to improve our ability to locate and remediate DNAPL present as chlorinated solvents. DNAPLs that are not viscous, such as chlorinated solvents, tend to sink into aquifer materials below the water table and become much more difficult to locate and remediate than non aqueous phase liquids that are lighter than water ( LNAPLs ) which tend to float at the water table when spilled into natural soils. The United States Environmental Protection Agency (USEPA) has focused considerable attention on

392-402: A fire in a confined space. In the first half of the 20th century, another common fire extinguisher was a single-use, sealed glass globe, a "fire grenade, " filled with carbon tetrachloride or salt water. The bulb could be thrown at the base of the flames to quench the fire. The carbon tetrachloride type could also be installed in a spring-loaded wall fixture with a solder -based restraint. When

441-446: A good solvent for many materials (such as grease and tar), carbon tetrachloride was widely used as a cleaning fluid for nearly 70 years. It is nonflammable and nonexplosive and did not leave any odour on the cleaned material, unlike gasoline , which was also used for cleaning at the time. It was used as a "safe" alternative to gasoline. It was first marketed as Katharin , in 1890 or 1892 and as Benzinoform later. Carbon tetrachloride

490-482: A mixture of carbon tetrachloride and carbon dioxide is heated to 350 degrees C, it gives phosgene: Reaction with hydrogen sulfide gives thiophosgene : Reaction with sulfur trioxide gives phosgene and pyrosulfuryl chloride : Reaction with phosphoric anhydride gives phosgene and phosphoryl chloride : Carbon tetrachloride reacts with dry zinc oxide at 200 degrees Celsius to yield zinc chloride , phosgene and carbon dioxide : Carbon tetrachloride

539-572: A red-hot tube, carbon tetrachloride dechlorinates to tetrachloroethylene and hexachloroethane . Carbon tetrachloride, when treated with HF , gives various compounds such as trichlorofluoromethane (R-11), dichlorodifluoromethane (R-12), chlorotrifluoromethane (R-13) and carbon tetrafluoride with HCl as the by-product: This was once one of the main uses of carbon tetrachloride, as R-11 and R-12 were widely used as refrigerants. An alcohol solution of potassium hydroxide decomposes it to potassium chloride and potassium carbonate in water: When

SECTION 10

#1733086199087

588-471: A stabiliser. Prior to the Montreal Protocol , large quantities of carbon tetrachloride were used to produce the chlorofluorocarbon refrigerants R-11 ( trichlorofluoromethane ) and R-12 ( dichlorodifluoromethane ). However, these refrigerants play a role in ozone depletion and have been phased out. Carbon tetrachloride is still used to manufacture less destructive refrigerants. Carbon tetrachloride

637-419: Is a chlorinated solvent can act as an ongoing pathway for constituents to dissolve into groundwater. Common use of chlorinated solvents in manufacturing operations began during World War II , with the rate of usage for most solvents increasing into the 1970s. By the early 1980s, chemical analyses becoming available that documented widespread contamination of groundwater with chlorinated solvents. Since that time,

686-451: Is a key ingredient that adds weight to the otherwise buoyant wax. One speciality use of carbon tetrachloride was in stamp collecting , to reveal watermarks on postage stamps without damaging them. A small amount of the liquid is placed on the back of a stamp, sitting in a black glass or obsidian tray. The letters or design of the watermark can then be seen clearly. Today, this is done on lit tables without using carbon tetrachloride. Being

735-583: Is a useful solvent for halogenations either by the elemental halogen or by a halogenation reagent such as N -bromosuccinimide (these conditions are known as Wohl–Ziegler bromination ). Between 1902 and 1908, carbon tetrachloride-based fire extinguishers began to appear in the United States, years after Europe. In 1910, the Pyrene Manufacturing Company of Delaware filed a patent to use carbon tetrachloride to extinguish fires. The liquid

784-500: Is assumed that carbon tetrachloride was still used as a dry cleaning solvent in North Korea as of 2006. Carbon tetrachloride was briefly used as a volatile inhalation anaesthetic and analgesic for intense menstruation pains and headaches in the mid-19th century. Its anaesthetic effects were known as early as 1847 or 1848. It was introduced as a safer alternative to chloroform by Doctor Protheroe Smith in 1864. In December 1865,

833-417: Is formed. After the synthesis of the dimethyl chlorophosphate, a further reaction (for example with a primary amine like aniline ) is possible by the following reaction equation: In this reaction, in addition to the starting compound dialkyl phosphite, tetrachloromethane and a base (an amine) are used in stoichiometric amounts. Only chloroform, which occurs after two reaction steps from tetrachloromethane,

882-515: Is one of the most potent hepatotoxins (toxic to the liver), so much so that it is widely used in scientific research to evaluate hepatoprotective agents. Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system and degenerate the liver and kidneys, and prolonged exposure may lead to coma or death. Chronic exposure to carbon tetrachloride can cause liver and kidney damage and could result in cancer . Consumption of alcohol increases

931-684: Is relevant as a waste product for the assessment of the atomic economy. It should furthermore be kept in mind that the product of the reaction has a greater molar mass than the starting compound. The atom economy of this reaction can therefore be classified as relatively good. The Atherton-Todd reaction is related to the Appel reaction . In the Appel reaction, tetrachloromethane is used for chlorination as well. Tetrachloromethane Carbon tetrachloride , also known by many other names (such as carbon tet for short and tetrachloromethane , also recognised by

980-435: Is used primarily by environmental engineers and hydrogeologists to describe contaminants in groundwater , surface water and sediments. DNAPLs tends to sink below the water table when spilled in significant quantities and only stop when they reach impermeable bedrock. Their penetration into an aquifer makes them difficult to locate and remediate. Examples of materials that are DNAPLs when spilled include: When spilled into

1029-429: Is used to cleave a methyl group of dimethyl phosphite. The intermediate 1 results from this reaction step. Subsequently, the intermediate 1 deprotonates the starting compound dimethylphosphite, so that intermediates 2a and intermediates 2b are formed. The intermediate 1 is then regenerated from the intermediate 2a . Finally, intermediate 2b is chlorinated by tetrachloromethane and dimethyl chlorophosphate 3

SECTION 20

#1733086199087

1078-752: The Momotombo Volcano in Nicaragua emits carbon tetrachloride at a flux of 82 grams per year while the global industrial emissions were at 2 × 10 grams per year. Carbon tetrachloride was found in Red algae Asparagopsis taxiformis and Asparagopsis armata . It was detected in Southern California ecosystems, salt lakes of Kalmykian Steppe and a common liverwort in Czechia. At high temperatures in air, it decomposes or burns to produce poisonous phosgene . This

1127-469: The Resource Conservation and Recovery Act Dense nonaqueous phase liquids (DNAPLs), have low solubility and are with viscosity markedly lower and density higher than water-asphalt, heavy oils, lubricants and also chlorinated solvents-penetrate the full depth of the aquifer and accumulate on its bottom. "DNAPL movement follows the slope of the impermeable strata underlying the aquifer and can move in

1176-425: The central nervous system and degenerate the liver and kidneys. Prolonged exposure can be fatal. In the carbon tetrachloride molecule , four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds . Because of this symmetric geometry, CCl 4 is non-polar. Methane gas has the same structure, making carbon tetrachloride

1225-420: The gallery ). CCl 4 has an atmospheric lifetime of 85 years. In organic chemistry , carbon tetrachloride serves as a source of chlorine in the Appel reaction . Carbon tetrachloride made from heavy chlorine-37 has been used in the detection of neutrinos . Carbon tetrachloride was widely used as a dry cleaning solvent, as a refrigerant , and in lava lamps . In the last case, carbon tetrachloride

1274-454: The 1950s, carbon tetrachloride was manufactured by the chlorination of carbon disulfide at 105 to 130 °C: But now it is mainly produced from methane : The production often utilizes by-products of other chlorination reactions , such as from the syntheses of dichloromethane and chloroform . Higher chlorocarbons are also subjected to this process named "chlorinolysis": The production of carbon tetrachloride has steeply declined since

1323-449: The 1980s because of environmental concerns and the decreased demand for CFCs , which were derived from carbon tetrachloride. In 1992, production in the U.S./Europe/Japan was estimated at 720,000 tonnes. Carbon tetrachloride was discovered along with chloromethane and chloroform in oceans , marine algae and volcanoes . The natural emissions of carbon tetrachloride are too little compared to those from anthropogenic sources; for example,

1372-518: The IUPAC ), is a chemical compound with the chemical formula CCl 4 . It is a non-flammable, dense, colourless liquid with a "sweet" chloroform -like odour that can be detected at low levels. It was formerly widely used in fire extinguishers , as a precursor to refrigerants , an anthelmintic and a cleaning agent , but has since been phased out because of environmental and safety concerns. Exposure to high concentrations of carbon tetrachloride can affect

1421-487: The Scottish obstetrician who discovered the anaesthetic effects of chloroform on humans, James Young Simpson , had experimented with carbon tetrachloride as an anaesthetic. Simpson named the compound "Chlorocarbon" for its similarity to chloroform. His experiments involved injecting carbon tetrachloride into two women's vaginas. Simpson orally consumed carbon tetrachloride and described it as having "the same effect as swallowing

1470-505: The anaesthetic use of carbon tetrachloride never gained popularity due to its potential toxicity. The veterinary doctor Maurice Crowther Hall (1881-1938) discovered in 1921 that carbon tetrachloride was incredibly effective as an anthelminthic in eradicating hookworm via ingestion. In one of the clinical trials of carbon tetrachloride, it was tested on criminals to determine its safety for use in human beings. Beginning in 1922, capsules of pure carbon tetrachloride were marketed by Merck under

1519-409: The early 1980s. Since carbon tetrachloride freezes at –23 °C, the fire extinguishers would contain only 89-90% carbon tetrachloride and 10% trichloroethylene ( m.p. –85 °C) or chloroform (m.p. –63 °C) for lowering the extinguishing mixture's freezing point down to temperatures as low as –45 °C. The extinguishers with 10% trichloroethylene would contain 1% carbon disulfide as

Atherton–Todd reaction - Misplaced Pages Continue

1568-482: The environment (e.g. spilled trichloroethene does not become lighter than water, it will remain denser than water). However, when the DNAPL is a more complex mixture, the density of the mixture can change over time as the mixture interacts with the natural environment. As an example, a mixture of trichloroethene and cutting oil may be released and originally be denser than water—a DNAPL. As the mixture of trichloroethene and oil

1617-401: The environment, chlorinated solvents are frequently present as DNAPL and the DNAPL can provide a long term secondary source of the chlorinated solvent to dissolved groundwater plumes. Chlorinated solvents are typically immiscible in water, having low solubility in water by definition, yet still have a solubility above the concentrations allowed by drinking water protections. Therefore, DNAPL which

1666-504: The name Necatorina (variants include Neo-necatorina and Necatorine ). Necatorina was used as a medication against parasitic diseases in humans. This medication was most prevalently used in Latin American countries. Its toxicity was not well understood at the time and toxic effects were attributed to impurities in the capsules rather than carbon tetrachloride itself. Due to carbon tetrachloride's toxicity, tetrachloroethylene (which

1715-480: The opposite direction to the groundwater gradient." Groundwater remediation technologies have been developed that can address DNAPL in some settings. Excavation is not always practicable due to the depths of the DNAPL, the dispersed nature of the residual DNAPL, mobility caused during excavation, and complexities with near-by structures. Technologies that are emerging for treatment include the following Most DNAPLs remain denser than water after they are released into

1764-423: The preparation were Acritet , Carbacryl and Acrylofume . The most common preparation, Acritet , was prepared with 34 percent acrylonitrile and 66 percent carbon tetrachloride. Dense nonaqueous phase liquid A dense non-aqueous phase liquid or DNAPL is a denser-than-water NAPL , i.e. a liquid that is both denser than water and is immiscible in or does not dissolve in water. The term DNAPL

1813-413: The presence of carbon tetrachloride in "very high concentrations" (up to 101 mg/m ) as a result of manufacturers' mixing of surfactants or soap with sodium hypochlorite (bleach). Carbon tetrachloride is also both ozone-depleting and a greenhouse gas . However, since 1992 its atmospheric concentrations have been in decline for the reasons described above (see atmospheric concentration graphs in

1862-462: The remediation of DNAPL which can be costly. Removal or in situ destruction of DNAPLs eliminates the potential exposure to the compounds in the environment and can be an effective method for remediation; however, at some DNAPL sites remediation of DNAPL may not be practicable, and containment may be the only viable remedial action. The USEPA has a program to address sites where DNAPL removal is not practicable for remediation projects under CERCLA under

1911-572: The solder melted by high heat, the spring would either break the globe or launch it out of the bracket, allowing the extinguishing agent to be automatically dispersed into the fire. A well-known brand of fire grenade was the "Red Comet", which was variously manufactured with other fire-fighting equipment in the Denver, Colorado area by the Red Comet Manufacturing Company from its founding in 1919 until manufacturing operations were closed in

1960-436: The toxic effects of carbon tetrachloride and may cause more severe organ damage, such as acute renal failure , in heavy drinkers. The doses that can cause mild toxicity to non-drinkers can be fatal to drinkers. The effects of carbon tetrachloride on human health and the environment have been assessed under REACH in 2012 in the context of the substance evaluation by France. In 2008, a study of common cleaning products found

2009-707: Was a common problem when carbon tetrachloride was used as a fire extinguisher: There have been deaths due to its conversion to phosgene reported. Carbon tetrachloride is a suspected human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals. The World Health Organization reports carbon tetrachloride can induce hepatocellular carcinomas (hepatomas) in mice and rats. The doses inducing hepatic tumours are higher than those inducing cell toxicity. The International Agency for Research on Cancer (IARC) classified this compound in Group 2B , " possibly carcinogenic to humans ". Carbon tetrachloride

Atherton–Todd reaction - Misplaced Pages Continue

2058-416: Was also investigated by Hall in 1925) replaced its use as an anthelmintic by the 1940s. It once was a popular solvent in organic chemistry, but because of its adverse health effects, it is rarely used today. It is sometimes useful as a solvent for infrared spectroscopy , because there are no significant absorption bands above 1600 cm . Because carbon tetrachloride does not have any hydrogen atoms, it

2107-405: Was also used as an alternative to petrol (gasoline) in dry shampoos , from the beginning of 1903 to the 1930s. Several women had fainted from its fumes during the hair wash in barber shops, the hairdressers often used electric fans to blow the fumes away. In 1909, a baronet 's daughter, Helenora Elphinstone-Dalrymple (aged 29), died after having her hair shampooed with carbon tetrachloride. It

2156-506: Was historically used in proton NMR spectroscopy . In addition to being toxic, its dissolving power is low. Its use in NMR spectroscopy has been largely superseded by deuterated solvents (mainly deuterochloroform ). The use of carbon tetrachloride in the determination of oil has been replaced by various other solvents, such as tetrachloroethylene . Because it has no C–H bonds, carbon tetrachloride does not easily undergo free-radical reactions . It

2205-431: Was originally synthesized in 1820 by Michael Faraday , who named it "protochloride of carbon", by decomposition of hexachloroethane ("perchloride of carbon") which he synthesized by chlorination of ethylene . The protochloride of carbon has been previously misidentified as tetrachloroethylene because it can be made with the same reaction of hexachloroethane. Later in the 19th century, the name "protochloride of carbon"

2254-470: Was recommended for regularly cleaning the type slugs of typewriters in office settings in the 1940s. Carbon tetrachloride was the first chlorinated solvent to be used in dry-cleaning and was used until the 1950s. It had the downsides of being corrosive to the dry-cleaning equipment and causing illness among dry-cleaning operators, and was replaced by trichloroethylene , tetrachloroethylene and methyl chloroform (trichloroethane). Carbon tetrachloride

2303-405: Was used for tetrachloroethylene, and carbon tetrachloride was called "bichloride of carbon" or "perchloride of carbon". Henri Victor Regnault developed another method to synthesise carbon tetrachloride from chloroform , chloroethane or methanol with excess chlorine in 1839. Kolbe made carbon tetrachloride in 1845 by passing chlorine over carbon disulfide through a porcelain tube. Prior to

2352-406: Was vaporized by the heat of combustion and extinguished flames, an early form of gaseous fire suppression . At the time it was believed the gas displaced oxygen in the area near the fire, but later research found that the gas inhibited the chemical chain reaction of the combustion process. In 1911, Pyrene patented a small, portable extinguisher that used the chemical. The extinguisher consisted of

2401-432: Was widely used as a fumigant to kill insect pests in stored grain. It was employed in a mixture known as 80/20, that was 80% carbon tetrachloride and 20% carbon disulfide . The United States Environmental Protection Agency banned its use in 1985. Another carbon tetrachloride fumigant preparation mixture contained acrylonitrile . Carbon tetrachloride reduced the flammability of the mixture. Most common trade names for

#86913