Halogenoalkane preparation

Nitriles can be prepared by the reaction of a halogenoalkane with KCN in aqueous ethanol. 

Frankland soon prepared more organometallics by reacting other metals with halogenoalkanes. The reaction mixtures were confined in sealed tubes and heated by focusing the sun s rays upon them. Frankland prepared the methyl and ethyl derivatives of mercury, tin and antimony, and also such compounds as oxide of stanethylium (diethyltin oxide, (C2H5)2SnO), which he formulated as C4H5SnO. 

An important method for preparing alkenes involves the elimination (an El or E2 mechanism) of HX from halogenoalkanes, RX (Section 5.3.2). Alcohols (ROH) can also be converted into alkenes by activating the OH group (e.g. by protonation or conversion into a tosylate) to make this into a better leaving group (Section 5.2.2). 

In the presence of strong bases, NH-imidazoles are alkylated via the imidazolyl anion, for example, Na-imidazolide (prepared from imidazole and NaOH) undergoes 1-alkylation (->8, R = alkyl) with halogenoalkanes and dialkyl sulfates [378]. Because of the ambident character of unsymmetrical imidazolyl anions (e.g., 9), base-induced alkylation of 4- or 5-substituted imidazoles affords mixtures of 1,4- and 1,5-disubstituted products, for example ... 

This reaction is not really suitable for preparing specific halogenoalkanes, because we get a mixture of substitution products. In the reaction between methane and chlorine, the products can include dichloromethane, trichloromethane and tetrachloromethane as well as chloromethane. These other products result from propagation steps in which a chlorine free radical attacks a halogenoalkane already formed. For example ... 

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