Alkyl halides Grignard reaction

Reaction XLIII. (a) Formation of Esters by the action of Acid Anhydrides or of Acid Chlorides on an Alcohol in the presence of Magnesium Alkyl Halide (Grignard). (B., 39, 1738.)—This application of the Grig-nard reaction to the preparation of esters is of theoretical rather than practical interest as illustrating the wide applicability of this many-sided reaction. The steps in the synthesis will be clear from the examples given they are somewhat different from the usual phases of a Grignard reaction. 

Common synthetic pathways to obtain mono-, di-, tri- and tetraalkylsilanes are reactions of the respective halogenosilanes with lithiated alkyl compounds, with alkyl-magnesium halides (Grignard reactions) and with alkyl halides in a Wurtz-Fittig-type reaction, as well as the addition of silanes to alkenes, i.e. hydrosilylation. 

In Chapter 15, Grignard reagents react as bases, but they are poor nucleophiles with alkyl halides. Grignard reagents are good nucleophiles with ketones or aldehydes, however, and these reactions will be discussed in more detail in Chapter 18. For the moment, the point of this example is to see that nucleophiles react with ketones and aldehydes by acyl addition. In each example, the alkoxide products 30-32 are converted to an alcohol via an acid-base reaction where the alkoxide is the base and aqueous acid (H+) is used. The alcohol product is the conjugate acid of this reaction and, because the hydronium ion is used as an acid, water is the conjugate base in this second reaction. This second chemical reaction is necessary in order to isolate a neutral product. 

Scheme 7.5. A series of reactions utilized to convert an alkyl halide (1-chlorobutane) to the corresponding alkyltin hydride. The alkyl halide, after reaction with magnesium to produce a Grignard reagent can be hydrolyzed to produce the alkane. The trialkyltin hyride can be used to convert other alkyl halides to their respective alkanes.

Strictly speaking the alkyl halides are esters of the halogen acids, but since they enter into many reactions (t.g., formation of Grignard reagents, reaction with potassium cyanide to yield nitriles, etc.) which cannot be brought about by the other eaters, the alkyl halides are usually distinguished from the esters of the other inorganic acids. The preparation of a number of these is described below. 

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