SCF studies

There have been three other studies of the lowest singlet PE surface of CH4. Two of these were SCF studies using a minimum basis set.61 62 Both predict a barrier height for the reaction (2) of > 209 kj mol-1. This is in agreement with orbital sym-... 

AX4. BF4 and CF4. The only calculation75 found on BF4 involved a rather small basis set SCF study. Although several papers have dealt with CF4 at a minimal basis set level, the more extended basis set results of Brundle et al.76 dementi et al.,77 and Adams and Clark78 have not been improved upon. 

N. Yamamoto, F. Bernardi, A. Bottoni, M. Olivucci, M. A. Robb, and S. Wilsey,J. Am. Cbem. Soc., 116, 2064 (1994), and references cited therein. Mechanism of Carbene Formation from the Excited States of Diazirine and Diazomethane An MC-SCF Study. 

J. Gu et al., A new insight into the structure and stability of hoogsteen hydrogen bonded g-tetrad an ab initio SCF study. Chem. Phys. Lett. 311, 209-214 (1999)... 

As (CH3)3P=CH2 is still too formidable a problem for theoretical chemists, the related but hypothetical H3P=CH2 molecule was the subject of the ab initio LCAO-MO-SCF studies published in 1972 (1). Using two uncontracted Gaussian basis sets, one with and the other without phos-... 

Palmer, I.J., Ragazos, I.N., Bernardi, F., Olivucci, M., and Robb, M.A. (1994) An MC-SCF study of the photochemical Paternd-Buchi reaction. Journal of the American Chemical Society, 116, 2121-2132. 

NHg, NH+, and NHj. The radical NHa was the first polyatomic free radical to be observed experimentally, and it has since been extensively studied spectroscopically. Bender and Schaefer 458 have referenced calculations on NHa prior to 1970, and have presented results for the most accurate calculations yet carried out, to which we return below. However, del Bene,459 at about the same time, reported the results of an SCF study, using small (STO-3G) or (ST04-31G) basis sets. The predicted zBi ground state of the radical has 0 = 108°, J (N—H) = 1.01 A, and for the Mi state 0 = 144°, 7 (N—H) = 0.98 A. 

Lithium ester enolates are extremely important in polymer chemistry as initiators and active centers of the anionic polymerization of acrylic and methacrylic monomers in polar solvents. Thus, HF-SCF studies, comparable to those mentioned above, were undertaken on monomeric methyl isobutyrate (MIB) enolate210,211. The overall conclusions on the aggregation and solvation trends are exactly the same, the bent rj3-0,C mode being preferred over the rj1-O planar one by ca 3.3 kcalmol-1. While the dimeric MIB enolate solvated by four molecules of THF was found to be the enthalpically most stable aggregate, the prismatic S6 unsolvated MIB hexamer was computed as the preferred structure in non-polar solvents (Scheme 55)212. In the latter case, the supplementary oxygen of the ester acting as a side-chain ligand for the lithium seems to explain this remarkable stability. 

Karpfen, A., and Yanovitskii, O, Cooperativity in hydrogen bonded clusters An improved ab initio SCF study on the structure and energetics of neutral, protonated and deprotonated chains of neutral, cyclic hydrogen fluoride oligomers, J. Mol. Struct. (Theochem) 314,211-227 (1994). 

R. Akesson, L. G. M. Pettersson, M. Sandstrom, P. E. M. Siegbahn, and U. Wahlgren, Theoretical ab Initio SCF Study of Binding Energies and Ligand Field Effects for the Hexahydrated Divalent Ions of the First-row Transition Metals, J. Phys. Chem. 96, 10773-10779 (1992). 

These can be further classified into two types the flow type for use in SCF chromatography coupled to NMR, and the autoclave type which can be used at pressures well in excess of those needed for the most common SCF studies. 

Bernard , F., Robb, M. A., Suzzi-Valli, G., Tagliavini, E., Trombini, C., Umani-Ronchi, A. An MC-SCF study of the transition structures for the aldol reaction of formaldehyde with acetaldehyde boron enolate. J. Org. Chem. 1991, 56, 6472-6475. 

These considerations are frequently overlooked in studies that claim, on numerical grounds, that 5 is an overcorrection, or simply unhelpful. For example, in an SCF study on FH. OH2 Kocjan et al observed that correction of the STO-2G result at the calculated removed all attraction. Their conclusion that overcorrects is debatable, however, since was probably so short that a repulsive corrected A should have been anticipated. 

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