Halides, alkyl, halogen

Halochromie,/. halochromism, halochromy. Halogen-, halogen, halo- (as in Halogenbenr zoeadure, Halogenpyridin, etc.), halide of (as in Halogenailber, silver halide), -alkyl, n. alkyl halide, -aryl, n. aryl halide. 

Other f-transition metal catalysts have been described by von Dohlen (4) and Throckmorton (5) as well as by Chinese (6, 7) and Italian (8-10) scientists. They generally consist of a rare earth compound, an aluminum alkyl, and a halide, the halogens being bound to the rare earth element or aluminum. 

Alkyl halides a halogen atom is bonded to an A/ 3-hybridized carbon. 

Organometallic compounds or carbanions undergo a number of reactions in which the carbanion or carbanion-like moiety of the organometallic compound acts as a nucleophilic displacing agent. Examples are the formation of hydrocarbons from alkyl halides, alkyl halides from halogens, and ketones from acid chlorides or esters. The latter two reactions are closely related to the base-catalyzed condensations and are perhaps additions as well as displacement reactions. Related addition reactions are the carbonation of organometallic compounds and the addition to ketones or aldehydes. 

The interaction of diaryl tellurides and the esters of halogenated fatty acids, e.g. methyl bromacetate, gives diarvl-telluretin halide alkyl esters, e.g. (C6H5)2Te(Br).CH2.COOCH3. The halogen present may be chlorine, bromine or iodine, moist silver oxide replacing the bromine by the hydroxyl group. 

Reaction XLIV. (b) Condensation of Alkyl and Aryl Halogen Compounds with the Sodio- and other Metallo-derivatives of Ethyl Aceto-acetate and its Homolognes. (A., 186, 214 201, 143 213, 143.)—Like malonic ester, acetoacetic ester contains two 1 3-carbonyl groups with a methylene group in position 2. It is only to be expected then that it yields with metallic sodium or sodium alcoholate sodio-derivatives from which mono- and di-, alkyl and aryl homologues can be obtained by treatment with a suitable halide, including halogen esters. Acetoacetic acid... 

Reaction XLVm. (a) Action of Alkali Cyanides on Alkyl and Acyl Halides. (Bl., [2], 50, 214.)—This reaction is capable of very wide application, all the simple alkyl halogen compounds, the acyl halides, and the halogen fatty acids come within its scope. The nitriles so formed yield acids by hydrolysis, so it is frequently the first step in the synthesis of an acid—the preparation and hydrolysis of the nitrile are often combined. The preparations of malonic, succinic, tricarballylic and other acids (Preparations 60, 61, 62) illustrate this. The extension of this reaction to acyl halides is important, and should be referred to, as should the interaction of silver cyanide, and alkyl iodides, to give isonitriles. Mercuric and silver cyanides, it may be noted, give with acyl chlorides and bromides better yields of normal acyl nitriles than do the alkali cyanides. 

The elimination of hydrogen halide (a halogen acid) from an alkyl halide requires a strong base such as the alkoxide ion, RO. Weaker bases such as the OH ion give poor yields of elimination product. 

In an alkyl halide, the halogen atom is bonded to an sp3 hybrid carbon atom. The halogen is more electronegative than carbon, and the C—X bond is polarized with a partial positive charge on carbon and a partial negative charge on the halogen. 

Halogen Exchange Reactions The Sn2 reaction provides a useful method for synthesizing alkyl iodides and fluorides, which are more difficult to make than alkyl chlorides and bromides. Halides can be converted to other halides by halogen exchange reactions, in which one halide displaces another. 

The rules that were given for naming alkanes in Section 3.4 are used for alkyl halides. A halogen is treated as an alkyl substituent. 

In naming alkyl halides by the IUPAC system, remember that a halogen is named as a substituent on an alkane. When numbering the alkyl halide, the halogens are numbered in the same way as alkyl groups and are cited alphabetically. 

Salts of sulfinic acids ace converted to sulfones by the action of pri-lary/ secondary, and benzyl halides, alkyl sulfates, and aryl halides in which the halogen atoms are activated by nitro groups in the ortbo or para positions. The reaction fails with t-amyl halide. The yields vary widely, depending upon the nature of the reactants. From salts of benzenesulfinic acid and simple alkylating agents, sulfones are produced in 50-90% yields. Satisfactory results have been obtained when the aryl sulfinic acid contains nitro, cyano, and acetamido groups. Keto sulfones are made in 48-62% yields by alkylation with a-halo ketones. ... 

Homologous Series of Alcohols.—As, hydroxyl substitution products of the hydrocarbons the alcohols form an homologous series analogous to that of the alkyl halides or halogen substitution products. Methyl and ethyl alcohol are thus the first two members of such a series derived from the methane or paraffin hydrocarbons. 

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