Carbon charge

Previously Issleib et a/.(1866,27) had found a clear relationship of J(P-H) with the 5 character, calculated from LCAO-MO orbitals, for PHf (ca. 140 Hz 17% r), PH3 (185 Hz 18% s) and PH (550 Hz 36% i).f Other factors, however, may contribute to these couplings, some arguments have been recently proposed(1969,50) to prove the importance of the phosphorus effective charge, similar to that found for the effect of the carbon charge on 13C-H coupling. (1965,X1)... 

Arenium ion energies (AAH ion - neutral) and changes in carbon charges [Aq = (ion) - q (neutral)] for protonation of 90 and 91 were probed by the AMI method. The singlet oxidation dication of 90 was also calculated. The charge delocalization modes in the PAH arenium ions were discussed and compared. The AMI studies indicated that benzo[<3]coronene cations were less delocalized than benzo[g/z/]perylene ions. Benzannelation (91 92) severely limited the conjugation path in the carboca-tions despite the fact that coronene 92 was still planar. Further benzannelation (92 90) had a minimal effect on the charge delocalization mode. 

This brings up the obvious question What are the true values of n and of the net carbon charge in ethane ... 

Here we examine the carbon net charges of ethane and ethylene, obtained from SCF and configuration interaction calculations, corrected by means of the appropriate p, determined for n = —4.4122. Remember that the same value of p applies to both ethane and ethylene, as n is solely determined by the effectiveness of the inductive effects. Equation (5.15) is used to get p, namely, p = 138.68 me in 4-31G + Cl calculations and thus, from Eq. (5.10), the corresponding carbon charges of ethane and ethylene (see Table 5.5). 

A multiple regression analysis using Eq. (5.9) and carbon charges corrected according to Eq. (5.10) leads to [38,44]... 

Note that at this point the carbon charges are expressed in a convenient dimensionless way or, if we prefer, in relative units, taking the ethane carbon atom as reference by setting its charge at one arbitrary unit. 

This rough estimate is to be taken cum grano salts (with a grain of salt)— it follows from energy calculations and bmte-force fits with experimental energy data [44]. It is probably not precise, because the contributions of the ip -carbon charge variations are rather small and likely to be blurred by uncertainties of the experimental energy data. 

Both = 35.1 me and q = 7.7me are the selected net carbon charges of ethane and ethylene, respectively. The difference between them is... 

It is difficult to assess how close the two sets of results really are. The first one evidently depends on the precision of the thermochemical data that have been used, namely, AHf and ZPE + Hj-— Hq- Equation (6.8), on the other hand, is accurate. It is perhaps our best means for testing sp carbon charges an error of 1 me in the evaluation of one of the carbons translates into an error of 0.5 kcal/mol in bond energy. Now, the two sets are too close to warrant revision of the procedure, yet we cannot endorse it for more than it is an acceptable approximation. For our needs, and for the time being, Eq. (6.8) solves the problem. Moreover, the reasoning is that if this approximation holds in the close neighborhood of nitrogen, it should be all the more acceptable for carbons in positions y, S, and so on. 

Derived from infrared intensities (Reference 169). Carbon charges were determined from H charges by symmetry arguments. h HF/6-31 G(d,p) calculations. This work. 

According to the New York Times (11/7/07), the actual average "wholesale" costs of one kWh of electricity in 2007 in the United States was as follows Pulverized Coal - 5.7c, Nuclear - 6.4c, Coal Gas - 6.6c, Natural Gas - 7.3c, Wind - 9.6c, Biomass - 10.7c, Solar Thermal -12.0c. These numbers do not yet reflect the coming carbon charges, nor do they reflect transportation and distribution costs required to... 

MCFC 2H2 + 2C032 — 2H20 + 2C02 + 4e immobilised molten carbonate charge carrier C032- 02 + 2C02 + 4e — 2C032 ... 

Figure 28 Typical chronopotentiometric profile of a disordered carbon charged-discharged in Li salt-alkyl carbonate solution. The carbon was a Li doped polyacenic semiconductor (PAS) obtained by heat treatment of phenolformaldehyde resin [348]. Note the high capacity, the sloping potential profile and the hysteresis between the charge and discharge routes. (With copyrights from Elsevier Science Ltd., 1998.)...

Carbon charge (tax) 0 Electricity S Nonfuel O M, %/yr of capital Fixed costs, %/yr of capital Capital charges ... 

Also given in Table 9.5 is the effect of distributing the cost of carbon emissions across only the olefins (ethylene and propylene) versus distributing this cost over all of the saleable products, i.e. that pyrolysis gasoline and other products should receive some of the carbon charge. The cost curves for the various scenarios are shown in Figure 9.15. 

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