Of halogen derivatives

Hydroxyalkylthiazoles are also obtained by cyclization or from alkoxyalkyl-thiazoles by hydrolysis (36, 44, 45, 52, 55-57) and by lithium aluminium hydride reduction of the esters of thiazolecarboxylic acids (58-60) or of the thiazoleacetic adds. The Cannizzaro reaction of 4-thiazolealdehyde gives 4-(hydroxymethyl)-thiazole (53). The main reactions of hydroxyalkyl thiazoles are the synthesis of halogenated derivatives by the action of hydrobroraic acid (55, 61-63), thionyl chloride (44, 45, 63-66), phosphoryl chloride (52, 62, 67), phosphorus penta-chloride (58), tribromide (38, 68), esterification (58, 68-71), and elimination that leads to the alkenylthiazoles (49, 72). 

Halogenation. Halogens and halogen acids add readily to the unsaturated carbon linkages of the cyclopentadiene molecule. By such additions a series of halogenated derivatives range, in the case of the chloride, from 3-chlotocydopentene to tetrachlorocyclopentane. Of all the possible chloto derivatives of CPD, only hexachlorocyclopentadiene [77-47-4] ever reached commercial status. It was used as an insecticide, but this use has been discontinued because of its toxicity (see Chlorocarbons and chlorohydrocarbons, toxic aromatics). It can be prepared by a Hquid phase chlorination of CPD below 50°C (29). 

Potassium tert-butylate leads to ignition of halogen derivatives, which is more or less immediate, depending on their nature and physical state two minutes with liquid dichloromethane and gaseous chloroform one minute with liquid carbon tetrachloride and epichlorhydrin immediate ignition with gaseous chloroform. 

It is important to recognize that the intermolecular long-distance bonding with the participation of halogen derivatives represents a specific example of the broad general area of donor/acceptor interactions. Moreover, the complexes of molecular iodine, bromine and chlorine with aromatic donors represent classic examples of charge-transfer compounds [26-28] that are vital for the development of Mulliken theory of intermolecular association [29-31]. The latter thus provides the convenient framework for the... 

Arbuzov, A.E. and Dunin, A.A., Action of halogen derivatives of aliphatic esters on alkyl phosphites, /. Russ. Phys. Chem. Soc., 46, 291, 1914. 

On the other hand, addition of tertiary amines accelerated hydrogenation of some compounds over Raney nickel [6I. In hydrogenation of halogen derivatives over palladium [62] or Raney nickel [63] the presence of at least one equivalent of sodium or potassium hydroxide was found necessary. 

A similar process may take place in the reduction of polar compounds with single bonds. A halogen, hydroxy, sulfhydryl or amino derivative by accepting an electron dissociates into a radical and an anion. In aprotic solvents the two radicals combine. In the case of halogen derivatives the result is Wurtz synthesis. In the presence of protons the anion is protonated and the radical accepts another electron to form an anion that after protonation gives a hydrocarbon or a product in which the substituent has been replaced by hydrogen. 

REDUCTION OF HALOGEN DERIVATIVES OF HYDROCARBONS AND BASIC HETEROCYCLES... 

Although acetylene still is used in a number of organic syntheses on an industrial scale, its use on a high-tonnage basis has diminished because of the lower cost of other starting materials, such as ethylene and propylene. Acetylene has been widely used in the production of halogen derivatives, acrylonitrile, acetaldehyde, and vinyl chloride. Within recent years, producers of acrylonitrile switched to propylene as a starting material. 

The following tables show the extinction coefficients in alcohol of halogen derivatives of cg/cZotelluropentane and the molecular conductivities (A25°) of these derivatives. The tertiary salts behave as strong electrolytes, like trimethyl tellurium iodide, but the secondary salts resemble dimethyl tellurium di-iodide in losing one molecule of halogen by hydrolysis, giving rise to hydroxyhalides. 

EXTINCTION COEFFICIENTS IN ALCOHOL OF HALOGEN DERIVATIVES OF CYCLOTELLUROPENTANE. 

One of the few anodic transformations of ketones in the presence of halogen derivatives which appears to involve anodic oxidation of the carbonyl compound itself is shown in... 

TABLE 3. Isomer ratio (%) in the mononitration of halogen derivatives of benzene and C o fullerene solubility in these derivatives [34] ... 

Although this method was unsatisfactory for DDT, excellent results were obtained with a wide variety of halogenated derivatives including acyclic, phenolic, aromatic, and steroid types. 

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