Alkyl halides Compounds with halogen from alcohols

Halogenations with dihalotriphenylphosphoranes have been reviewed briefly by Fieser and Fieser.4 Dibromotriphenylphos-phorane appears to have been studied somewhat more than the dichloro compound, but both reagents effectively convert alcohols to alkyl halides, carboxylic acids and esters to acid halides, etc. The reaction of 1,2-epoxycyclohexane with dibromotriphenylphos-phorane under conditions similar to those described here gives a mixture of cis- and trans-1,2-dibromocyclohexanes. A reagent prepared from triphenylphosphine and carbon tetrachloride has been used for similar transformations.5... 

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... 

V) The ester of malonic acid, like acetacetic ester, possesses the property in virtue of which one of the two methylene hydrogen atoms can be replaced by sodium, in consequence of the acid properties imparted by the two neighbouring carbonyl (CO) groups. When the sodium compound is treated with organic halides, like alkyl halides, halogen derivatives of add-esters, acid-chlorides, etc., the sodium is replaced by alkyl residues, add residues, etc-, just as in the case of the dosely related acetacetic ester. In the above-mentioned examples, the sodium salt of the malonic ester is first formed from sodium alcoholate and the ester ... 

The use of organic halogen compounds as the starting products for the synthesis of other organic chemicals is too immense a field to do more than indicate some of the commercial applications. In his book I4S) on the chemistry of petroleum derivatives, Ellis includes a chapter on the production of alcohols and esters from alkyl halides, and also one on miscellaneous reactions of halo-paraffins and cycloparaffins. The manufacture of amyl alcohols and related products from the chlorides has been well covered 14 ) 1 )-A two-step process for the synthesis of cyclopropane by chlorinating propane from natural gas and dechlorinating with zinc dust was devised in 1936 152). A critical review of syntheses from l,3-dichloro-2-butene was published in Russia in 1950 (1-54). The products obtainable from the allylic chlorides are covered in a number of articles 14If 14 157). 

A second method of preparing the hydrocarbon illustrates another principle which is important, as it can be applied to the preparation of many compounds which show the behavior of ethylene. When an alkyl halide, ethyl bromide for example, is heated with an alcoholic solution of potassium hydroxide, the base removes one hydrogen and one halogen atom. In this way ethylene can be prepared from ethyl bromide —... 

Identification of Alkyl Halides.—On account of their relative inertness at ordinary temperatures the alkyl halides are usually identified by the determination of their physical properties. They are insoluble in concentrated sulphuric acid, and, unlike the acyl halides, they do not react readily with water and alcohols. Unlike the compounds in which halogen is joined to nitrogen, they are not easily changed by an aqueous solution of sodium hydroxide. They are distinguished from many halogen derivatives of benzene and related hydrocarbons, which will be described later, by the fact that they are decomposed when boiled with an alcoholic solution of potassium hydroxide —... 

At about the same time, Alexander W. Williamson (England 1824-1904) showed how ethers ethers contain the C-O-C linkage) could be prepared from the potassium salt of an alcohol (an alcohol contains a C-O-H unit). The potassium salt is the conjugate base of that alcohol, C-0 K+, and the oxygen atom of that species reacts with an alkyl halide, which contains a C-X bond. In this representation, X is a halogen and alkyl is the term used for a unit containing carbons and hydrogen atoms. The nomenclature for all of these compounds will be described in Chapters 3 and 4. 

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