Grignard reagents acidic hydrogen atoms

Reduction of an alkyl halide, either via the Grignard reagent or directly with metal and acid, involves simply the replacement of a halogen atom by a hydrogen atom the carbon skeleton remains intact. This method has about the same applicability as the previous method, since, like alkenes, alkyl halides are generally prepared from alcohols. Where either method could be used, the hydrogenation of alkenes would probably be preferred because of its simplicity and higher yield. 

The cyclotrimerization of nitriles (R—CN) is a very common route to 1,3,5-triazi-nes.10-12,119-121 The reaction conditions and catalysts are dependent on the R part of the nitrile molecule several reaction mechanisms are involved in the trimerization reaction. Aliphatic and aromatic nitriles can trimerize upon application of high pressure and/or heat however, catalysts are used more frequently, e.g. hydrogen chloride, ehlorosulfonic acid, boron trifluoride, sodium metal, Grignard reagents and sodium triphenylmethanide. The same also applies to all other nitriles (a-atom not carbon). 

Grignard reagents react with the terminal hydrogen atoms of 1-alkynes by an acid—base reaction, and this is a useful method for the preparation of aUcynylmagnesium halides and alkynyllithiums. 

It is not possible to prepare a Grignard reagent from a compound that contains any hydrogen more acidic than the hydrogen atoms of an alkane or alkene. 

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