Organic halides, Grignard reagents

Grignard reagents, organomagnesium halides, are prepared by the reaction of metallic magnesium with a wide range of organic halides (reaction 9.3). Dry ether type solvents are essential. 

Many organic halides do not react satisfactorily with lithium to form RLi ecMnpounds or with metallic magnesium to form Grignard reagents. The desired organolithium compound can often be prepared by a halogen-metal interconversion reaction ... 

Grignard reagents are prepared from organic halides by reaction with magnesium a Group II metal... 

Grignard reagents are normally prepared by the slow addition of the organic halide to a stirred suspension of magne.sium turnings in the appropriate solvent and with rigorous exclusion of air and moisture. The reaction, which usually begins slowly after an induction period, can be initiated by addition of a small crystal of iodine this penetrates the protective layer of... 

A convenient method for generating carbon nucleophiles is to combine an organic halide, RX, with magnesium metal. This yields RMgX, a Grignard reagent . 

Polarization also occurs in coupling and disproportionation reactions of Grignard reagents with alkyl halides. The vinyl protons of isobutene produced in the reaction of t-butylmagnesium chloride with t-butyl bromide show A/E polarization as do the methyl protons of isobutane (Ward et al., 1970). Similar results arise in the reaction of diethyl-magnesium with organic halides (Kasukhin et al., 1972). 

Structural types for organometallic rhodium and iridium porphyrins mostly comprise five- or six-coordinate complexes (Por)M(R) or (Por)M(R)(L), where R is a (T-bonded alkyl, aryl, or other organic fragment, and Lisa neutral donor. Most examples contain rhodium, and the chemistry of the corresponding iridium porphyrins is much more scarce. The classical methods of preparation of these complexes involves either reaction of Rh(III) halides Rh(Por)X with organolithium or Grignard reagents, or reaction of Rh(I) anions [Rh(Por)] with alkyl or aryl halides. In this sense the chemistry parallels that of iron and cobalt porphyrins. 

The formation of Grignard reagents takes place at the metal surface. Reaction commences with an electron transfer to the halide and decomposition of the radical ion, followed by rapid combination of the organic group with a magnesium ion.1 It... 

Grignard reagents are powerful nucleophiles => it is not possible to prepare a Grignard reagent from any organic halide that contains a carbonyl, epoxy, nitro, or cyano group. 

This means that when we prepare Grignard reagents, we are effectively limited to alkyl halides or tro analogous organic halides containing C=C bonds, internal triple bonds, ether linkages, and -NR2 groups. 

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