Nitromethane general

Watanabe and coworkers have described some Co -bipyridyl (phenanthroline) catalyzed Michael additions of nitromethane generalized by equation (49) but the catalyzing effect of the complex remains obscure.292... 

Much of the early work was inconclusive confusion sprang from the production by the reaction of water, which generally reduced the rate, and in some cases by production of nitrous acid which led to autocatalysis in the reactions of activated compounds. The most extensive kinetic studies have used nitromethane,acetic acid, sulpholan,i and carbon tetrachloride as solvents. 

The chemical resistance of the linear polymers is also very good. Resistant to most acids, aqueous bases, hydrocarbons, most halogenated hydrocarbons, alcohols and phenols, they are attacked by concentrated sulphuric acid, formic acid, some amines, benzaldehyde, nitromethane and a few other reagents. They will dissolve in 1-chloronaphthalene at elevated temperatures but in general have excellent solvent resistance. The polymer is cross-linked by air oxidation at elevated temperatures. 

A mixture of nitromethane and hexafluorobenzene, when thermolyzed at 550 °C, yields pentafluorotoluene and pentafluorophenol as major products- The formation of nitrosyl and mtryl fluondes is probably a dnving force in this transfor-madon [705] A potential general preparative route to various perfluorovmyl amines is pyrolytic decarboxylation of potassium salts of perfluoro-2-(dialky-... 

A detailed study of spectra of compounds 1, 2, and 3 has been published as part of a general study of azolopyridines (84OMR209). The shifts are shown in Table III. The N shifts have been used to determine the structure of 7-amino-triazolopyridines 128 and 129 (89T7041). The shifts recorded were 56.8, 56.2 (Nl), 245.4, 246.3 (N2), 320.6, 316.8 (N7a), all from nitromethane as standard at 380 ppm the absorption for the amine was at 345.5, 350 ppm in accordance with the amino structure shown, rather than the imino forms 128a and 129a. 

Although the base-catalyzed addition of nitroalkanes to electron-deficient olefins has been extensively used in organic synthesis fsee Michael addition Chapter 4, it is only recently that the reaction has been extended to the cyclopropanadon reaction. In 1978, it was reported that the anion of nitromethane reacts with certain highly electron-deficient olefins to produce cycloptopanesingoodyieldrEq. 7.36. More recently, this reaction has been extended to more general cyclopropanadons, as shown in Eqs. 7.37 and 7.38, in which potassittm salts of nitroalkanes are employed in DMSO as alkylidene transfer reagents." ... 

In general, nitrations in nitromethane show a greater tendency towards zeroth-order kinetics, so that, for example, whereas benzene gives first-order kinetics on nitration by 7.0 M nitric acid in acetic acid (Table 13), in nitro-... 

The condensation of nitro compounds and imines, the so-called aza-Henry or nitro-Mannich reaction, has recently emerged as a powerful tool for the enantioselective synthesis of 1,2-diamines through the intermediate /3-amino nitro compounds. The method is based on the addition of a nitronate ion (a-nitro carbanion), generated from nitroalkanes, to an imine. The addition of a nitronate ion to an imine is thermodynamically disfavored, so that the presence of a protic species or a Lewis acid is required, to activate the imine and/or to quench the adduct. The acidic medium is compatible with the existence of the nitronate anion, as acetic acid and nitromethane have comparable acidities. Moreover, the products are often unstable, either for the reversibility of the addition or for the possible /3-elimination of the nitro group, and the crude products are generally reduced, avoiding purification to give the desired 1,2-diamines. Hence, the nitronate ion is an equivalent of an a-amino carbanion. 

The photodecomposition and thermodecomposition of nitromethane have been extensively studied as model systems in combustion, explosion and atmosphere pollution processes[l]. On another hand, nitromethane was selected as a model solvent in experiments aimed at examining non hydrogen-bonded solvent effects in a general acid-base theory of organic molecules [2.3]. This selection is based on the electronic and structural characteristics of nitromethane that has a high dielectric constant, and at the same time cannot form hydrogen bonds with solute molecules. 

The origin of the change in sign of ASt is revealed when the [Ln(DMF)8]3+ exchange process is studied in inert d3-nitromethane diluent (11,93). For Ln3 + = Tb3+, Er3+, Tm3+, the general form of the DMF exchange rate equation is as in Eq. (27). When Ln3+ = Tb3+, the second term on the right-hand side dominates. Both terms are im-... 

Olah, G. A. et al., J. Inorg. Nucl. Chem., 1960, 14, 295-296 Experimental directions must be followed exactly to prevent violent spontaneous explosions during preparation of the salt from silver oxide and boron trifluoride etherate in nitromethane, according to the earlier method [1], The later method [3] is generally safer than that in [2],... 

Chlorination of nitromethane following the published general method [1] gave a product which decomposed explosively during distillation at 95 mbar [2], A b.p. of 122°C/1 bar is quoted in the literature. 

The heterobimetallic asymmetric catalyst, Sm-Li-(/ )-BINOL, catalyzes the nitro-aldol reaction of ot,ot-difluoroaldehydes with nitromethane in a good enantioselective manner, as shown in Eq. 3.78. In general, catalytic asymmetric syntheses of fluorine containing compounds have been rather difficult. The S configuration of the nitro-aldol adduct of Eq. 3.78 shows that the nitronate reacts preferentially on the Si face of aldehydes in the presence of (R)-LLB. In general, (R)-LLB causes attack on the Re face. Thus, enantiotopic face selection for a,a-difluoroaldehydes is opposite to that for nonfluorinated aldehydes. The stereoselectivity for a,a-difluoroaldehydes is identical to that of (3-alkoxyaldehydes, as shown in Scheme 3.19, suggesting that the fluorine atoms at the a-position have a great influence on enantioface selection. 

Products of a so-called vinylogous Wolff rearrangement (see Sect. 9) rather than products of intramolecular cyclopropanation are generally obtained from P,y-unsaturated diazoketones I93), the formation of tricyclo[2,1.0.02 5]pentan-3-ones from 2-diazo-l-(cyclopropene-3-yl)-l-ethanones being a notable exception (see Table 10 and reference 12)). The use of Cu(OTf), does not change this situation for diazoketone 185 in the presence of an alcoholl93). With Cu(OTf)2 in nitromethane, on the other hand, A3-hydrinden-2-one 186 is formed 160). As 186 also results from the BF3 Et20-catalyzed reaction in similar yield, proton catalysis in the Cu(OTf)2-catalyzed reaction cannot be excluded, but electrophilic attack of the metal carbene on the double bond (Scheme 26) is also possible. That Rh2(OAc)4 is less efficient for the production of 186, would support the latter explanation, as the rhodium carbenes rank as less electrophilic than copper carbenes. 

The aci-form of the nitro group is frequently claimed in pure chemistry. However, only ad-nitromethane appears to have been comprehensively studied as an isolated species15. Ionized keto-enol systems are characterized by reversal of the relative stabilities of the single species compared to their neutral counterparts. Thus, the ionized enols are generally the thermodynamically more favoured tautomers by approximately 15-20 kcalmol-1, the... 

It will be helpful at this point to review a few well-known features of the electrochemical behavior of nitro and nitroso compounds. The reader is referred to a previous review in this series for more detail on this point1. The primary fact of which one must be aware of is that the electrochemistry of nitro compounds is exclusively cathodic the high oxidation level of nitrogen in the nitro group means that while they are easily reduced, they generally cannot be oxidized. As a matter of fact, nitrobenzene and nitromethane have been used as solvents for electrochemical oxidations because of their stability under anodic conditions2. Nitroso compounds are readily both oxidized and reduced, although the literature on these substances is much more sparse. 

Secondary nitro compounds can be converted into carbanions in similar fashion. Interesting highly functionalized adducts (46) were prepared by addition to levoglucosene (45) (equation 17)59. Mixtures of diastereomeric adducts were generally formed60. The adduct from nitromethane undergoes double Michael addition followed by aldol condensation to afford the novel adduct 47. 

To minimize the effects of viscosity for purposes of comparing data between solvents, plots areoften made using the product of the ion mobility and the viscosity (Walden product) in place of mobility alone. A plot of the Walden product against the reciprocal of the crystallographic radii for several solvents is shown in Fig. 6. Arbitrary curves have been drawn to indicate general trends. Values in solvents for which precise transference numbers and conductance data are available, such as acetonitrile and nitromethane, give smooth curves. 

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