Acetonitrile protonated

Reduction of stilbene [18] or dipheny-lacetylene [214] in DME yields 1,2,3,4-tetraphenylbutane, whereas phenanthrene [214] provides 9,9, 10,10 -tetra-hydro-9.9 -biphenanthrene. Hydrodimerization was also observed with benzalfluo-rene [225]. If DME is replaced by acetonitrile, protonation completely dominates hydrodimerization [18]. In carefully dried ethers, using alkali or alkaline earth metals salts as supporting electrolyte, 1,1-diphenylethylene can be reduced ca-thodicaUy to give stable solutions of 1,1,4,4-tetraphenylbutane dianions [226]. These dianions can be cleaved by flash... 

A sample of the protein, horse heart myoglobin, was dissolved in acidified aqueous acetonitrile (1% formic acid in HjO/CHjCN, 1 1 v/v) at a concentration of 20 pmol/1. This sample was injected into a flow of the same solvent passing at 5 pl/min into the electrospray source to give the mass spectrum of protonated molecular ions [M + nH] shown in (a). The measured ra/z values are given in the table (b), along with the number of protons (charges n) associated with each. The mean relative molecular mass (RMM) is 16,951,09 0.3 Da. Finally, the transformed spectrum, corresponding to the true relative molecular mass, is shown in (c) the observed value is close to that calculated (16,951.4), an error of only 0.002%. 

The protonated azirine system has also been utilized for the synthesis of heterocyclic compounds (67JA44S6). Thus, treatment of (199) with anhydrous perchloric acid and acetone or acetonitrile gave the oxazolinium perchlorate (207) and the imidazolinium perchlorate (209), respectively. The mechanism of these reactions involves 1,3-bond cleavage of the protonated azirine and reaction with the carbonyl group (or nitrile) to produce a resonance-stabilized carbonium-oxonium ion (or carbonium-nitrilium ion), followed by attack of the nitrogen unshared pair jf electrons to complete the cyclization. 

Gas Phase (DGB) Basicities (333 K) [94JCS(P2)2341], Basicity Constants (pA bh+) Measured in Acetonitrile (25°C) (91KGS836), and MNDO PM3 Calculation [94JCS(P2)2341] PROTON AEEiNmES (PA) OF Compounds... 

The Heck reaction is considered to be the best method for carbon-carbon bond formation by substitution of an olefinic proton. In general, yields are good to very good. Sterically demanding substituents, however, may reduce the reactivity of the alkene. Polar solvents, such as methanol, acetonitrile, N,N-dimethylformamide or hexamethylphosphoric triamide, are often used. Reaction temperatures range from 50 to 160 °C. There are various other important palladium-catalyzed reactions known where organopalladium complexes are employed however, these reactions must not be confused with the Heck reaction. 

In the presence of a catalytic amount of concentrated hydrochloric acid, dimethyl 1 -methyl-1 H-l-benzazepine-3,4-dicarboxylate (1) undergoes addition of 1-methylindole, probably via initial protonation of the enaminic 3-position of the benzazepine ring, to give the indolyldihydrobenz-azepine 2.21 In fact, adduct 2 is the major product from the reaction of 1-mcthylindole with dimethyl acetylenedicarboxylate in acetonitrile. Similar adducts are obtained with indole. 

Similar stereochemical results were obtained from the addition of the potassium and lithium ions of ethyl acetate, /V,V-dimethylacetamide, acetonitrile, acetophenone and pinacolone to 3-(/erf-butyldimethylsilyloxy)-T-phenylsulfonyl-1-cyclohexene followed by protonation or methylation of the resulting sulfonyl carbanion intermediates7. 

In another investigation (Loewenschuss et al., 1976) dediazoniation was studied in TFE and in acetonitrile in the presence of pyridine. There is UV and NMR evidence for the formation of a diazopyridinium cation in addition, -CIDNP absorption and emission signals were observed. Systems containing diazonium salts and pyridine are important in industrial chemistry, as pyridine is used as a proton acceptor in the diazo coupling reaction (see Sec. 12.8) in a considerable number of syntheses of azo dyes. At the same time pyridine has an unfavorable effect on the yield because of the competing homolytic dediazoniation. 

Obviously, this shift implies the self-association of DMSO. Further frequency shifts to even lower wave numbers (1050-1000 cm " ) are observed in both aprotic polar and protic solvents. In aprotic solvents such as acetonitrile and nitromethane, the association probably takes place between the S—O bond of DMSO and the —C=N or the —NOz group in the molecules by dipole-dipole interaction as shown in Scheme 331,32. Moreover, the stretching frequency for the S—O bond shifts to 1051 cm 1 in CHC13 and to 1010-1000 cm -1 in the presence of phenol in benzene or in aqueous solution33. These large frequency shifts are explained by the formation of hydrogen bonds between the oxygen atom in the S—O bond and the proton in the solvents. Thus, it has been... 

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