Alkyl halides toxicity

The amines are a group of compounds with the general formula R-NHj, and all the common amines are hazardous. As a class the amines pose more than one hazard, being flammable, toxic, and, in some cases, corrosive. The amines are an analogous series of compounds and follow the naming pattern of the alkyl halides and the alcohols that is, the simplest amine is methyl amine, with the molecular formula of CH NHj. Methyl amine is a colorless gas with an ammonia-like odor and an ignition temperature of 806°F. It is a tissue irritant and toxic, and it is used as an intermediate in the manufacture of many chemicals. Ethyl amine is next in the series, followed by propyl amine, isopropyl amine, butyl amine and its isomers, and so on. 

As alkylating agent an alkyl halide, alkyl tosylate or dialkyl sulfate is used in most cases the latter type of reagent is often used in the preparation of methyl and ethyl ethers by employing dimethyl sulfate and diethyl sulfate respectively. Dimethyl sulfate is an excellent methylating agent, but is acutely toxic as well as carcinogenic." ... 

The haloalkanes (also called alkyl halides) are alkanes in which at least one hydrogen atom has been replaced by a halogen atom. Although they have important uses, many haloalkanes are highly toxic and a threat to the environment. The haloalkane 1,2-dichlorofluoroethane, CHC1FCH2C1, is an example of a chlorofluorocarbon (CFC), one of the compounds held responsible for the depletion of the ozone layer (see Box 13.3). Many pesticides are aromatic compounds with several halogen atoms. 

Reagents that provide UV adsorptive derivatives of carboxylic acids are fairly numerous. The preparation of the simple benzyl esters by reacting the carboxylic ion with alkyl halides or diazo compounds has been unsuccessful due to their having unacceptable toxicity. The... 

Rhodium catalyzed carbonylations of olefins and methanol can be operated in the absence of an alkyl iodide or hydrogen iodide if the carbonylation is operated in the presence of iodide-based ionic liquids. In this chapter, we will describe the historical development of these non-alkyl halide containing processes beginning with the carbonylation of ethylene to propionic acid in which the omission of alkyl hahde led to an improvement in the selectivity. We will further describe extension of the nonalkyl halide based carbonylation to the carbonylation of MeOH (producing acetic acid) in both a batch and continuous mode of operation. In the continuous mode, the best ionic liquids for carbonylation of MeOH were based on pyridinium and polyalkylated pyridinium iodide derivatives. Removing the highly toxic alkyl halide represents safer, potentially lower cost, process with less complex product purification. 

Historically, the rhodium catalyzed carbonylation of methanol to acetic acid required large quantities of methyl iodide co-catalyst (1) and the related hydrocarboxylation of olefins required the presence of an alkyl iodide or hydrogen iodide (2). Unfortunately, the alkyl halides pose several significant difficulties since they are highly toxic, lead to iodine contamination of the final product, are highly corrosive, and are expensive to purchase and handle. Attempts to eliminate alkyl halides or their precursors have proven futile to date (1). 

This process provides an option to avoid the expense and handling of toxic alkyl halides in the course of conducting Rh based carbonylations to carboxylic acids. The mechanism is still not completely clear and future work will be dedicated to clarifying the key chemical pathways that permitted us to omit the alkyl halides which were previously regarded as indispensable to the reaction. 

Tin-based reagents are not always snitable owing to the toxicity of organotin derivatives and the difficulties often encountered in removing tin residues from the final product. Therefore, the same authors have carried out additional experiments with 17d and several different alkyl halides under tin-free conditions. The treatment of 16d with tert-butyldiphenylsilyl chloride (TBDPSCl) and triethylamine in the presence of silver triflate in CH2CI2 affords the bis(silyloxy)enamine 17d in 92% yield (Scheme 17). When the radical reaction was carried out with ethyl iodoacetate in the presence of 2,2 -azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as the initiator in CH2CI2, the oxime ether 19 was obtained in 83% yield (Scheme 17). 

The normal-propylamine NPT has been made by the oxalylamide route, with the amide with a mp 179-181 °C (75%) from benzene and NPT hydrochloride mp 186-187 °C (33%) from MeOH/benzene. An attempt to make NPT by the alkyl halide procedure failed. Using these same ratios of reactants, there was the formation of a sizable quantity of DPT with appreciable unreacted tryptamine presence (T NPT DPT/1 5 4). A recycling under the same conditions gave T NPT DPT/0 3 7) and a third cycle gave only DPT, but with a loss of almost 90% of the material presumably to quaternary salt formation. Interestingly NPT is less toxic than DPT in experimental mice, but has not been assayed yet in man. 

The simple dialkyl sulphates, in particular dimethyl sulphate, are markedly toxic (see Section 4.2.24, p. 430). They may be characterised as the alkyl 2-naphthyl ethers (cf. alkyl halides, Section 9.6.8, p. 1251 and also Expt 6.111). 

There is one method of direct alkylation of a nitrogen nucleophile. Preliminary FGI (with reduction in mind again) to an alkyl azide 52 allows C-N disconnection to the alkyl halide and azide ion 54. This interesting species is linear and can slip into crowded molecules like a tiny dart. But there is a drawback all azides are toxic and POTENTIALLY EXPLOSIVE. 

The chemical reactivities of organohalide compounds vary over a wide range. The alkyl halides are generally low in reactivity, but may undergo pyrolysis in flames to liberate noxious products, such as HC1 gas. Alkenyl halides may be oxidized, which in some cases produces highly toxic phosgene, as shown by the following example ... 

The toxicities of alkyl halides vary a great deal with the compound. Although some of these compounds have been considered to be almost completely safe in the past, there is a marked tendency to regard each with more caution as additional health and animal toxicity study data become available. Perhaps the most universal toxic effect of alkyl halides is depression of the central nervous system. Chloroform, CHC13, was the first widely used general anesthetic, although many surgical patients were accidentally killed by it. 

Of all the alkyl halides, carbon tetrachloride has the most notorious record of human toxicity, especially for its toxic effects on the liver. For many years it was widely used in consumer products as a degreasing solvent, in home fire extinguishers, and in other applications. However, numerous toxic effects, including some fatalities, were observed, and in 1970, the U.S. Food and Drug Administration (FDA) banned the sale of carbon tetrachloride and formulations containing it for home use. 

Generally considered to be among the least toxic of the alkyl halides, 1,1,1-trichloroethane was once produced at levels of several hundred million kilograms per year. However, it is persistent in the atmosphere and is a strong stratospheric ozone-depleting chemical, so production has been severely curtailed and there is now little reason for concern over its toxicity. 

Allyl[mA(trimethylsilyl)]silane (87) and allyl alkyl sulfone (93), instead of toxic allyltributyltin, can be used for the allylation of alkyl halides under the same conditions as shown below (eqs. 4.34a-4.34c) [96-104]. 

Alkyl halides are used primarily as industrial and household solvents. Carbon tetrachloride (CC14) was once used for dry cleaning, spot removing, and other domestic cleaning. Carbon tetrachloride is toxic and carcinogenic (causes cancer), however, so dry cleaners now use 1,1,1-trichloroethane and other solvents instead. 

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