Dimethyl electron donor

Dimethyl carbonate (DMC) is a colorless liquid with a pleasant odor. It is soluble in most organic solvents but insoluble in water. The classical synthesis of DMC is the reaction of methanol with phosgene. Because phosgene is toxic, a non-phosgene-route may be preferred. The new route reacts methanol with urea over a tin catalyst. However, the yield is low. Using electron donor solvents such as trimethylene glycol dimethyl ether and continually distilling off the product increases the yield. ... 

AG° was calculated for eleven amines, ranging from 2,4-dinitroaniline (AG° = + 50 kJ mol-1) to aniline ( — 41), 4-morpholinoaniline ( — 99), and 4-dimethyl-aminoaniline ( — 108). The results demonstrate clearly that a primary electron transfer is very likely, at least for those aniline derivatives with a strong electron donor in the 4-position. 

The sterically unbiased dienes, 5,5-diarylcyclopentadienes 90, wherein one of the aryl groups is substituted with NO, Cl and NCCHj), were designed and synthesized by Halterman et al. [163] Diels-Alder cycloaddition with dimethyl acetylenedicarbo-xylate at reflux (81 °C) was studied syn addition (with respect to the substituted benzene) was favored in the case of the nitro group (90a, X = NO ) (syrr.anti = 68 32), whereas anti addition (with respect to the substituted benzene) is favored in the case of dimethylamino group (90b, X = N(CH3)2) (syn anti = 38 62). The facial preference is consistent with those observed in the hydride reduction of the relevant 2,2-diaryl-cyclopentanones 8 with sodium borohydride, and in dihydroxylation of 3,3-diarylcy-clopentenes 43 with osmium trioxide. In the present system, the interaction of the diene n orbital with the o bonds at the (3 positions (at the 5 position) is symmetry-forbidden. Thus, the major product results from approach of the dienophile from the face opposite the better n electron donor at the (3 positions, in a similar manner to spiro conjugation. Unsymmetrization of the diene % orbitals is inherent in 90, and this is consistent with the observed facial selectivities (91 for 90a 92 for 90b). 

The anaerobic redaction of dimethyl snlfide to methane (Oremland et al. 1989), and of dibenzyl disulfide to toluenethiol and finally tolnene (Miller 1992) has been described. Methanomethylovorans hollandica is able to grow anaerobically with both dimethyl sulfide and methanethiol (Lomans et al. 1999) whereas dimethyl sulfide, which is used as an electron donor for the growth of Rhodobacter sulfidophilus, is converted into dimethyl sulfoxide (Hanlon et al. 1994). 

Substituents modulate the electron-donor or acceptor strengths depending upon their electron-releasing or electron-withdrawing properties as evaluated by the Hammett a+ (or a) constant(s).62 For example, the multiple substitution of methyl groups on ethylene leads to the strong re-donor 2,3-dimethyl-2-... 

In a very special system, the photoelectrochemical regeneration of NAD(P)+ has been performed and applied to the oxidation of the model system cyclohexanol using the enzymes HLADH and TBADH. In this case, tris(2,2 -bipyridyl)ruthenium(II) is photochemically excited by visible light [43]. The excited Ru(II) complex acts as electron donor for AT,AT -dimethyl-4,4 -bipyridinium sulfate (MV2+) forming tris(2,2 -bipyridyl)ruthenium(III) and the MV-cation radical. The Ru(III) complex oxidizes NAD(P)H effectively thus... 

Some pairs of very strongly electron-donor and electron-acceptor monomers, such as p-methoxystyrene and dimethyl cyanofumarate, undergo spontaneous alternating copolymerizations without any added free-radical initiator, although heat may be required [Hall and Padias, 1997, 2001]. Initiation involves reaction of the comonomer pair to form a diradical,... 

The presence of the reversed field along the negative axis permits cations with stereoactive lone pairs to bond to other cations using the lone pair as an electron donor, but only if the bond to the second cation is shorter than Yq. This accounts for the ability of cations near the top of the periodic table to bond to other cations through their lone pairs as discussed in Section 3.5, e.g. N " " bonding to Cu + in Cu(N02), 8 + in NH4Co(S03)2(NH3)4 3H2O (36406) and dimethyl-sulphoxide, and in Pt(P03)4. Copper also forms complexes with AsOj" and possibly also very weak complexes with Se and Ge. ... 

Silacyclohexadienes may, in principle, act as 4-electron donors. Indeed, l,l-dimethyl-l-silacyclohexa-2,4-diene reacts with iron penta-carbonyl to give a complex in which the diene fragment is bonded to iron (50) ... 

Other systems using electron-donor compounds have been tried or are in development. Such compounds include trwz-butyl phosphate, dimethyl-fonuamide, trietliyleneglycol dimethyl ether, dimelliylsulfoxide, hexain-ethylphosphoramide, diethyleneglycol dimethyl ether, tricresyl phosphate, and dioxanc. Most of these compounds arc expensive compared with inorganic compounds used in other scrubbing systems. 

The ground states of electron donor-acceptor complexes between fraws-stilbene and electron-deficient alkenes (fumaronitrile, dimethyl fumarate and maleic anhydride) are formed and the isomerization of /runs-stilbene (and of fumaronitrile to maleic nitrile) has... 

A closely related organized microheterogeneous system has been composed of a Si02 colloid on which a Pd catalyst is immobilized, and the photosystem includes eosin, Eo2 (2), as photosensitizer, iV,A -dibenzyl-4,4 -(3,3 -dimethyl)bipyridinium, BMV2+ (15), as electron relay and TEOA as electron donor [137]. In a... 

Other Co(II)-complexes that were applied in the photosensitized reduction of C02 to CO (and concomitant H2-evolution) include Co(II)-ethylene glycol dimethyl ether complexes [178], and different tetraaza-macrocyclic Co(II)-complexes such as 27,28. A closely related system, where Ni(II)-tetraaza macrocycle (29) substitutes the cobalt homogeneous complexes in the photosystem including Ru(bpy) + as photosensitizer and ascorbic acid as electron donor, has been reported by Tinnemans [181] and Calvin [182],... 

Hydrogenase, HyD, includes a Fe-S cluster as active site. Photogenerated N,A -dimethyl-4,4 -bipyridinium radical cation, MV+, mediates H2-evolution in the presence of HyD [201-203], see Fig. 40. Different photosensitizers such as Ru(bpy) +, Zn-TMePyP4+ or acridine orange and sacrificial electron donor, i.e. ethylenediamine tetraacetic acid, EDTA, mercaptoethanol or cysteine, have been... 

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