78-00-2 tetraethyllead

The tolerable weekly intake (TWI) levels set by World Health Organization for methyl mercury is 1.6 pg/kg body weight. The reference dose (RfD) set by the U.S. EPA is 

EPA Designated Toxic Waste, RCRA Waste Number PI 10 DOT Label Poison, Flam mable Liquid 

Tetraethyllead is used as an additive to gasoline to prevent knocking in motors. However, because of its high toxicity and the pollntion problem, its nse in gasoline has been drastically cnrtailed. 

Combustible liquid flash point 72°C (163°F). It is least combustible among the heavy metal alkyls. The fire hazard is significantly low. The rate and spontaneity of air oxidation is also low. However, because of its moderate endothermicity (A// within the range -1-215 kcal/mol), it should be reasonably unstable and therefore susceptible to violent decomposition. Heating, rigorous agitation or prolonged contact with oxidants and nonmetal halides should, therefore, be considered a potential hazard. It is liable to explode if exposed to air for several days. 

Tetraethyllead is highly toxic by oral route. The LD50 values for rats, mice, and rabbits were all found to be 15mg/kg when administered by the oral, intravenous, subcutaneous, intraperitoneal, and parenteral routes. It may be absorbed through the skin causing lead poisoning. It is toxic to the central nervons system. The toxicity, however, is low to moderate by dermal route. It is an acute as well as chronic toxicant. The toxic effects are insomnia, hypotension, tremor, hypothermia, pallor, weight loss, hallucination, nansea, convulsion, and coma. The toxicity of this compound by inhalation route is also low to moderate. Because of its low vapor pressure, 0.2 torr at 20°C (68°F), inhalation hazard is relatively low. 

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Lead, like tin, forms only one hydride, plumbane. This hydride is very unstable, dissociating into lead and hydrogen with great rapidity. It has not been possible to analyse it rigorously or determine any of its physical properties, but it is probably PbH4. Although this hydride is unstable, some of its derivatives are stable thus, for example, tetraethyllead, Pb(C2Hj)4, is one of the most stable compounds with lead in a formal oxidation state of + 4. It is used as an antiknock in petrol. 

Ethyl Chloride. Most ethyl chloride [75-00-3] is produced by the hydrochlorination of ethylene (qv) using anhydrous HCl. Historically, the primary use of ethyl chloride was for the manufacture of tetraethyllead (TEL), a primary component of antiknock mixes in gasolines. Use has declined as a... 

The future use of lead may be decided by the resolution of an environmental paradox. Some markets for lead are being phased out because of environmental concerns, eg, the use of tetraethyllead as a gasoline additive. However, a 1990 State of California law and similar laws in nine eastern U.S. states require that 2% of new cars meet 2ero-emission standards in 1998. By 2003 this requirement rises to 10% of new vehicles. Zero emission vehicles are generally accepted to mean electric, ie, battery powered cars, and there is considerable research effort to bring suitable electric vehicles to market by 1998. 

Strong acids and strong alkaUes can severely bum the skin, chromium compounds can produce skin rashes, and repeated exposure to solvents causes removal of natural oils from the skin. Infection is always a concern for damaged skin. Absorption through the skin is possible for materials that are appreciably soluble iu both water and oil, eg, nitrobenzene, aniline, and tetraethyllead. Other materials can be absorbed if first dissolved iu extremely good solvents, eg, dimethyl sulfoxide. Subcutaneous iujection can occur accidentally by direct exposure of the circulatory system to a chemical by means of a cut or scratch or iuadvertent penetration of the skin with a hypodermic needle. 

Sodium amalgam is employed ia the manufacture of sodium hydroxide sodium—potassium alloy, NaK, is used ia heat-transfer appHcations and sodium—lead alloy is used ia the manufacture of tetraethyllead and tetramethyUead, and methylcyclopentadienylmanganesetricarbonyl, a gasoline additive growing ia importance for improving refining efficiency and octane contribution. 

After 1950, benzene in motor fuel was largely replaced by tetraethyllead but the demand for benzene in the chemical industry persisted and soon exceeded the total production by the coal carbonization industry. To meet this growing demand, methods for producing benzene directiy from petroleum sources were developed. 

Metal carbonyls have been used as antiknock compounds in unleaded gasoline (see Gasoline and other motor fuels). The Ethyl Corp. marketed methylcyclopentadienyknanganese tticarbonyl (MMT) however, as in the case of tetraethyllead (180), its use is prohibited because of environmental concerns. 

Tetraethyllead can be manufactured by the reaction of ethyl chloride with lead-sodium alloy (see Lead compounds). 

The halogen influences the rate of reaction, and, in general, the order of reactivity is HI > HBi > HCl. Impoitant uses of etfiyl chloiide include the manufacture of tetraethyllead and ethylceUulose. Ethyl bromide can be used to produce ethyl Grignard reagent and various ethyl amines. 

Ethyl Chloride. Previously a significant use for industrial ethanol was the synthesis of ethyl chloride [75-00-3] for use as an intermediate in producing tetraethyllead, an antiknock gasoline additive. Ethanol is converted to ethyl chloride by reaction with hydrochloric acid in the presence of aluminum or zinc chlorides. However, since about 1960, routes based on the direct addition of hydrochloric acid to ethylene or ethane have become more competitive (374,375). 

The main catalyst site poison for many years was tetraethyllead [78-00-2] even after use of unleaded gasoline. Not only is lead a catalyst... 

The mechanism of poisoning automobile exhaust catalysts has been identified (71). Upon combustion in the cylinder tetraethyllead (TEL) produces lead oxide which would accumulate in the combustion chamber except that ethylene dibromide [106-93-4] or other similar haUde compounds were added to the gasoline along with TEL to form volatile lead haUde compounds. Thus lead deposits in the cylinder and on the spark plugs are minimized. Volatile lead hahdes (bromides or chlorides) would then exit the combustion chamber, and such volatile compounds would diffuse to catalyst surfaces by the same mechanisms as do carbon monoxide compounds. When adsorbed on the precious metal catalyst site, lead haUde renders the catalytic site inactive. 

Experiments continued to find an appropriate form of lead that could at the same time prevent the formation of oxide deposits. Ethylene was found to combine with lead to form tetraethyllead (TEL), a stable compound that satisfied this requirement. 

The transfer of an ethyl group, in particular, can be performed with high diastereoselectivity by the use of tetraalkyllead, activated with titanium(IV) chloride14"15 (Table 4). The order of addition of the reagents exhibits a strong influence on the chemical yield and diastercoselectiv-ity of the addition reaction. Typically, titanium(IV) chloride is added at -78CC to the aldehyde, followed by addition of tetraethyllead. Poor yields and diastereoselectivity are observed if titanium(IV) chloride is first added to tetraethyllead followed by addition of the aldehyde ... 

Tetraethyllead fluid in four gasolines supplied by the Ethyl Corporation was determined by the comparative method on weighed samples, aluminum serving as standard. These tetraethyllead fluids could have contained dibromo- or dichloroethane, or both, in addition to the lead compound. 

The values of x in column 4 were obtained by the Ethyl Corporation by a chemical method, for which the estimated precision is 0.02 ml of tetraethyllead fluid per gallon. Comparison of columns 4 and 5 shows agreement within these limits for all samples except B62M-3 the reason for the considerably greater discrepancy here is unknown. The precision of the x-ray work is better than was expected. (The precision is sufficiently great to warrant consideration of the difference in the x-ray absorption of the base stocks, samples AOT-1 and B62M-1.) Further-... 

Table 3-4. Determination of Tetraethyllead Fluid in Leaded Gasoline...

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