Grignard reagents hydrocarbon formation

This reaction can be used for the synthesis of hydrocarbons but it may also take place as a side-reaction during generation of a Grignard reagent from an alkyl halide and magnesium, then leading to formation of undesired side-products. 

The foregoing results highlight the questions of the exact nature of the radicals involved in Grignard reagent formation and why the amount of hydrocarbon formed increases when changing solvent from THF to ether. 

It is unreasonable to believe that a model that assumes that the radicals diffuse freely in solution could account for such results. On the other hand, a surface-bound radical is fully in accord with them. Compound (S)-(-l-)-18 behaves similarly when exposed to metal surfaces of alkali metals in hydroxylic solvents [94]. As in the Grignard reagent formation, when a solution of (S)-(-f)-l-bromo-l-methyl-2,2-diphenylcyclopropane 18 in methanol, isopropyl alcohol, or r-butenol was exposed to an alkali metal, such as lithium, sodium, or potassium, the resulting hydrocarbon (K)-( —)-l-methyl-2,2-diphenylcyclopropane 13 was shown to be optically active and with retained configuration, as shown in Table 19 and Scheme 40. 

Alcohols react with HX to form alkyl halides, but the reaction works well only for tertiary alcohols, R,COH. Primaiy and secondary alkyl halides are normally prepared from alcohols using either SOClj or PBr ). Alkyl halides react with magnesium in ether solution to form organomagnesium halides, or Grignard ret ents (RM O- Since Grignard reagents are both nucleophilic and basic, they react with acids to yield hydrocarbons. The overall result of Grignard formation and protonation is the conversion of an alkyl halide into an alkane (RX— RM RH). 

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