Ethane protonated

C lOs6p2dlf5s3p2d f) basis set [a C) = 0.80] is referred to as TZ2P +/ whereas TZ2P(/protonated ethane complexes, standard 6-3 G dp) and 6-311G( fp) basis sets were employed. ... 

Protonated ethane, C2H2, the key intermediate in this mechanism, arises from protonation at the C-C or C-H bonds, which react as a-electron donors to give three-center two-electron bonds. 

Many mechanistic implications have been discussed, but we will concentrate here only on the most important structures in the context of dihydrogen-cation complexes. Deuterium-labeled methane and methyl cations were employed to examine the scrambling and dissociation mechanisms. The protonated ethane decomposition yields the ethyl cation and dihydrogen. Under the assumption that the extra proton is associated with one carbon only, a kinetic model was devised to explain the experimental findings, such as H/D scrambling. ... 

Charge density analysis has been carried out for three reaction paths involving intramolecular hydrogen transfer the keto-enol tautomerism of acetaldehyde, the pinacol rearrangement of protonated ethane-1,2-diol, and the unimolecular decomposition of methanediol, reactions involving H-transfer between C O, C C, and O O atoms.288... 

MO calculations on simple species of particular interest for hydride motion are those on protonated methane, CH, and protonated ethane, C2H (Pronin and Holer, 1981 Pronin and Karchenko, 1982 Minyaev and Pavlov, 1982). These species have been examined (Raghavachari et al., 1981) by ab initio methods using extended basis sets with polarization functions, and corrections for the effects of electron correlation have been applied. At... 

The reaction occurs by Sn2 displacement of water from a protonated ethane molecule by the oxygen atom of a second ethanol. 

Hydride bridging, 145, 147 cyclodecyl cation, 147 diborane, 147 ethyl cation, 147 protonated ethane, 147... 

Calculations on protonated ethane show that C2H5+-H2, described as a loose solvated-ion species, is a likely new isomer, along with the bridged ( tc c protonated) and open (ac n protonated) isomers. It is proposed that interaction of carbenium ions such as ethyl and isopropyl with saturated alkanes always results in... 

A very important characteristic of spin-spin splitting is that protons that have the same chemical shift do not split each other s signal Ethane for example shows only a single sharp peak m its NMR spectrum Even though there is a vicinal relationship between the protons of one methyl group and those of the other they do not split each other s signal because they are equivalent... 

Lower alkanes such as methane and ethane have been polycondensed ia superacid solutions at 50°C, yielding higher Hquid alkanes (73). The proposed mechanism for the oligocondensation of methane requires the involvement of protonated alkanes (pentacoordinated carbonium ions) and oxidative removal of hydrogen by the superacid system. 

For the stable conformers 13a-c of a substituted ethane the vicinal HH coupling constants 3Hz for syn-protons and 15 Hz for anti-protons can be derived from Fig. 2.18. If there is rotation around the C-C single bond, the coupling protons pass through the syn configuration twice and the anti configuration once. 

Thioketals are readily formed by acid-catalyzed reaction with ethane-dithiol. Selective thioketal formation is achieved at C-3 in the presence of a 6-ketone by carrying out the boron trifluoride catalyzed reaction in diluted medium. Selective protection of the 3-carbonyl group as a thioketal has been effected in high yield with A" -3,17-diketones, A" -3,20-diketones and A" -3,l 1,17-triones in acetic acid at room temperature in the presence of p-toluenesulfonic acid. In the case of thioketals the double bond remains in the 4,5-position. This result is attributed to the greater nucleophilicity of sulfur as compared to oxygen, which promotes closure of intermediate (66) to the protonated cyclic mercaptal (67) rather than elimination to the 3,5-diene [cf. ketal (70) via intermediates (68) and (69)]." " ... 

Figure 13.14 The origin of spin-spin splitting in bromo-ethane. The nuclear spins of neighboring protons, indicated by horizontal arrows, align either with or against the applied field, causing the splitting of absorptions into multiplets.

The proton NMR spectrum shows chem shifts of 6.93 5.957- (Ref 1). Photolysis with a Hg arc lamp gives N, nitrous oxide, methane, and ethane (Ref 2). It was found to produce colon and rectal carcinomas in rats after oral administration at 12mg/kg weekly, induction period 235 days (Ref 3)... 

Stronger reducing agents than Cu1 can be used for reactions that are related to the classical Meerwein reaction. Tim salts not only catalyze the formation of aryl radicals from diazonium ions but, as shown by Citterio and Vismara (1980) and Cit-terio et al. (1982 a), in stoichiometric proportions they also reduce the primary aryl-ethane radical to the arylethyl anion, which is finally protonated by the solvent SH (Scheme 10-61). This method is the subject of a contribution to Organic Syntheses (Citterio, 1990), in which 4-(4 -chlorophenyl)buten-2-one is obtained in 65-75% yield from 4-chlorobenzenediazonium chloride and but-3-en-2-one. 

The occurrence of proton transfer reactions between Z)3+ ions and CHa, C2H, and NDZ, between methanium ions and NH, C2HG, CzD , and partially deuterated methanes, and between ammonium ions and ND has been demonstrated in irradiated mixtures of D2 and various reactants near 1 atm. pressure. The methanium ion-methane sequence proceeds without thermal activation between —78° and 25°C. The rate constants for the methanium ion-methane and ammonium ion-ammonia proton transfer reactions are 3.3 X 10 11 cc./molecule-sec. and 1.8 X 70 10 cc./molecule-sec., respectively, assuming equal neutralization rate constants for methanium and ammonium ions (7.6 X 10 4 cc./molecule-sec.). The methanium ion-methane and ammonium ion-ammonia sequences exhibit chain character. Ethanium ions do not undergo proton transfer with ethane. Propanium ions appear to dissociate even at total pressures near 1 atm. 

Such is not the case, and furthermore, the presence of NHS does not alter product ratios in favor of the more highly deuterated species as it does in the methane systems. The additional observation that C2D6 is untouched in TD/D2 C2H6/C2D6 mixtures (Table III, System III) makes the evidence against ethanium ion-ethane proton transfer conclusive. 

Substrate reduction by vanadium nitrogenase has not been investigated as extensively as has molybdenum nitrogenase, but there are clear differences. Acetylene is a poor substrate and N2 does not compete as effectively with protons for the electrons available during turnover. Therefore, high rates of H2 evolution are observed in the presence of these substrates. Furthermore, acetylene is reduced to both ethylene and a minor product, ethane (172). Equation (2) summarizes the most efficient N2 reduction data yet observed for vanadium nitrogenase. 

H NMR data has been reported for the ethylzinc complex, Zn(TPP—NMe)Et, formed from the reaction of free-base N-methyl porphyrin H(TPP—NMe) with ZnEti. The ethyl proton chemical shifts are observed upheld, evidence that the ethyl group is coordinated to zinc near the center of the porphyrin. The complex is stable under N2 in the dark, but decomposed by a radical mechanism in visible light.The complex reacted with hindered phenols (HOAr) when irradiated with visible light to give ethane and the aryloxo complexes Zn(TPP—NMe)OAr. The reaction of Zn(TPP—NMe)Et, a secondary amine (HNEt2) and CO2 gave zinc carbamate complexes, for example Zn(TPP—NMclOiCNEti."" ... 

The proposed reaction mechanism involves intermolecular nucleophilic addition of the amido ligand to the olefin to produce a zwitterionic intermediate, followed by proton transfer to form a new copper amido complex. Reaction with additional amine (presnmably via coordination to Cn) yields the hydroamination prodnct and regenerates the original copper catalyst (Scheme 2.15). In addition to the NHC complexes 94 and 95, copper amido complexes with the chelating diphosphine l,2-bis-(di-tert-bntylphosphino)-ethane also catalyse the reaction [81, 82]. 

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