Compound grignard

The chemiluminescence of the reaction of Grignard reagents with oxygen was noted as early as 1906 [39], but only recently has some progress been made in understanding the mechanism of this reaction [40,41]. The following facts appear to be clearly established  

1) Free radicals are formed during the reaction (proved by the behaviour of the reaction mixture in an external magnetic field, and by ESR). 

2) The emission has maxima at 330 nm [41] or 357 nm [40], making Grignard chemiluminescence one of the most exergonic reactions of this type, requiring reaction enthalpies of at least 378kJ/mol. 

There has been disagreement about the emitting species. p-Terphenyl (formed in 0.1% yield) was suggested [40] as the emitter since the emission spectrum of phenyl magnesium bromide oxidation matches the fluorescence spectrum of terphenyl obtained from an authentic sample (40). 

This statement, however, has been challenged [41] because little resemblance of that spectrum to the literature spectrum [42] was found.An isomeric mixture of brominated biphenyls and an associated reaction mechanism were proposed instead [41]. It has been pointed out [43] that authentic brominated biphenyls have not been available for comparison. 

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Acetylenic Grignard compounds or the corresponding organoalkali metal derivatives are important intermediates in many syntheses of acetylenic compounds. The various methods for their formation in organic solvents and in liquid ammonia have been discussed extensively and we here give only a brief summary. 

Grignard compounds, more recent investigations have led to a better insight into... 

Benzyl chloride readily forms a Grignard compound by reaction with magnesium in ether with the concomitant formation of substantial coupling product, 1,2-diphenylethane [103-29-7]. Benzyl chloride is oxidized first to benzaldehyde [100-52-7] and then to benzoic acid. Nitric acid oxidizes directly to benzoic acid [65-85-0]. Reaction with ethylene oxide produces the benzyl chlorohydrin ether, CgH CH20CH2CH2Cl (18). Benzylphosphonic acid [10542-07-1] is formed from the reaction of benzyl chloride and triethyl phosphite followed by hydrolysis (19). 

Diazirines (3) smoothly add Grignard compounds to the N—N double bond, giving 1-alkyldiaziridines. Reported yields are between 60 and 95% without optimization (B-67MI50800). The reaction is easily carried out on a preparative scale without isolation of the hazardous diazirines and may serve as an easy access to alkylhydrazines. The reaction was also used routinely to detect diazirines in mixtures. The diaziridines formed are easily detected by their reaction with iodide. Phenyllithium or ethylzinc iodide also add to (3) with diaziridine formation. 

Diazirine, fluoromethoxy-nitrogen extrusion, 7, 224 Diazirine, methylvinyl-rearrangement, 7, 221 Diazirines addition reactions to Grignard compounds, 7, 2 0 as carbene precursors, 7, 236 IR spectra, 7, 203 microwave spectrum, 7, 199 molecular spectra, 7, 202-204 nitrogen extrusion, 7, 223 NMR, 7, 202 photoconversion to diazoalkanes, 7, 234 photoisomerization, 7, 221 photolysis, 7, 225-227 quantum chemical investigations, 7, 197 reactions... 

The stereochemistry of the 1,4-addition to A -octal-l-one and 1,1-di-methyl-A -octal-2-one has been investigated by House and Marshall, respectively. In summary, steric and stereoelectronic factors play a part in the mechanism of conjugate addition of Grignard compounds. With methylmagnesium iodide, the introduction of an axial methyl group into steroidal 5a-A -3-ketones (3) and 5 -A -3-ketones (6) is favored by stereo-electronic factors in the transition state. 

Diaziridine Syntheses from Diazirines and Grignard Compounds... 

A further synthesis of 1-alkyl-diaziridines is the addition of Grignard compounds to the NN double bond of diazirines [Eq. (35) ]. The... 

A modern variant is the intramolecular magnesium-ene reaction, e.g. the reaction of the alkene-allylic-Grignard compound 9 to give the five-membered ring product 10. This reaction proceeds regio- and stereoselectively, and is a key step in a synthesis of the sesquiterpenoid 6-protoilludene ... 

Since the formation of the Grignard compound takes place at the metal surface, a metal oxide layer deactivates the metal, and prevents the reaction from starting. Such an unreactive metal surface can be activated for instance by the addition of small amounts of iodine or bromine. 

Whereas aryl Grignard compounds afford good yields of sulfones with sulfonyl fluorides298 299, phenyllithium is mainly chlorinated by a-toluene-sulfonyl chloride on the other hand, the corresponding fluoride yields only a trace of the expected mono-sulfonylation product, while the main product is 26 obtained by twofold sulfonylation300 (equation 61). 

Scheme 27 Mechanism for the iron-catalyzed preparation of Grignard compounds [41]...

Because in the case of a sterically crowded imidazolide the formation of a carbinol is more difficult, reaction with the titanium reagent or the corresponding Grignard compound produces the allyl ketone in about the same yield [96]... 

Determination of the structures of Grignard reagents continues to be of interest, and reviews on this subject have appeared.126,127 Most of the structure authentications are done on crystalline materials, although solution studies performed with extended X-ray absorption fine structure (EXAFS) spectroscopy are also available. The Grignard compounds MeMgBr and EtMgBr in BunzO were studied at room temperature and —85 °C with EXAFS. At both temperatures, dimers are observed (Mg-(/r-Br) = 2.5 A Mg-O = 2.0 A).128... 

Li, Na, or Grignard compounds of cyclopentadiene, indene, or fluorene add to di-substituted cyclopropenium cations forming cyclopentadienyl cyclopropenes, which can be transformed to calicenes by subsequent hydride abstraction and deprotonation, as shown by the following examples 9S91 and 9992 (cf. p. 13) ... 

The weak chemiluminescence of Grignard compounds in air has been known since 1906. A radical chain mechanism similar to that of hydrocarbon autoxidation appears to provide the excitation energy of the emitting product. Until recently the relations between constitution and chemiluminescence in Grignard compounds were rather obscure j>-chloro-phenylmagnesium chloride was found to be the most efficient compound. 

Some of the first observations of luminescence accompanying electrolysis were reported by Bancroft in 1914, when halides were electrolyzed at mercury and other anodes [1], Thirteen years later luminescence was observed by Dufford et al. when Grignard compounds in anhydrous ether were electrolyzed, at the anode or cathode, by applying 500 to 1500 volts [2], and subsequently by Harvey for luminol in alkaline solution at the anode, by applying 2.8 volts [3],... 

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