Molecular Orbital Calculations on the

Recently H. L. Jones and D. L. Beveridge have presented molecular orbital calculations on the electronic structure of 2,3-pyrid5me explaining the exclusive formation of 2-aminopyridine from this intermediate [Tetrahedron Letters No. 24, 1577 (1964)]. 

Semi-empirical molecular orbital calculations on the phosphorane (96)... 

Pullman, B., and A. Pullman. 1974. Molecular Orbital Calculations on the Conformation of Amino Acid Residues of Proteins. Adv. Protein Chem. 28, 347-526. 

Molecular Orbital Calculations on the Conformation of Amino Acid Residues of Proteins... 

Ultraviolet spectra of benzoic acid in sulphuric acid solutions, published by Hosoya and Nagakura (1961), show a considerable medium effect on the spectrum of the unprotonated acid, but a much smaller one in concentrated acid. The former is probably connected with a hydrogen-bonding interaction of benzoic acid with sulphuric acid which is believed to be responsible for a peculiarity in the activity coefficient behaviour of unprotonated benzoic acid in these solutions (see Liler, 1971, pp. 62 and 129). The absence of a pronounced medium effect on the spectra in >85% acid is consistent with dominant carbonyl oxygen protonation. In accordance with this, Raman spectra show the disappearance in concentrated sulphuric acid of the carbonyl stretching vibration at 1650 cm (Hosoya and Nagakura, 1961). Molecular orbital calculations on the structure of the carbonyl protonated benzoic acid have also been carried out (Hosoya and Nagakura, 1964). 

ASED (Atom Superposition and Electron Delocalization) molecular orbital calculations on the formation of monomeric 1-triazolylborane by the process BH3-I-triazole H2-f H2B(Tz) indicate... 

Wolfe S, Kim CK, Yang K. Ab initio molecular orbital calculations on the neutral hydrolysis and methanolysis of azetidinones, including catalysis by water. Relationship to the mechanism of action of P-lactam antibiotics. Can J Chem 1994 72 1033-1034. 

Table 5 UHF-PM3 Molecular Orbital Calculations on the Radical Anions of Cyanonaphthalenes...

Molecular orbital calculations have also provided theoretical justification for these stereoelectronic effects in tetracovalent and pentacovalent phosphorus species (2-7). As has been shown in molecular orbital calculations on the X -P-X2 (X = 0,N) structural fragments, the X.-P bond is strengthened (as indicated by an increase in the Mulliken overlap population) while the P-X3 bond is weakened when the X atom lone pair is app to the P-X3 bond. Thus, in the g,t conformation of dimethyl phosphate (Structure ll the overlap population for the trans P-0 bond is. 017 electron lower than the overlap population for the gauche P-0 bond. As shown for g,t dimethyl phosphate one lone pair (shaded in 1) on the gauche bond oxygen is app to the trans bond, while no lone pairs on the trans bond oxygen are app to the gauche bond. Thus, the weakest X.-P bond has one app lone pair and no lone pairs on X. app to the P=X2 bond. 1... 

Further ab initio molecular orbital calculations on the reaction profile for the base-catalyzed hydrolysis of dimethyl phosphate in various ester conformations have provided support for this theory (5 6) ... 

Broer, R., Duijnen P.Th. van and Nieuwpoort W.C., Ab initio molecular orbital calculations on the active site of papain. Chem Phys. Lett. (1976) 42 525-529. 

In this section we shall review previous attempts to assign the spectra of ferric haemoproteins, and we shall also consider an interesting molecular orbital calculation on the haem chromophore. 

Table 4.3. Ab-initio molecular orbital calculations on the hydrogen-bonded water dimer. Variation of geometry with level of approximation [290]...

Pullman B, Pullman A (1974) Molecular orbital calculations on the conformation of amino acid residues of proteins. Adv Protein Chem 28 347 - 526... 

Saran A, Perahia D, Pullman B (1973) Molecular orbital calculations on the conformation of nucleic acids and their constituents. VII. Conformation of the sugar ring in -nucleosides the pseudorotational representation. Theor Chim Acta (Berlin) 30 31-44... 

O Malley, P. J., and J. Dwyer (1988). Ah initio molecular orbital calculations on the siting of aluminum in the Theta-1 framework some general guidelines governing the site preferences of aluminum in zeolites. Zeolites 8, 317-21. 

Carvalho et al. reported molecular orbital calculations on the electron-rich rhenium isocyanide complex ReCl(CNH)(H2PCH2CH2PH2) and the aminocarbyne complex [ReCl(CNH2)(H2PCH2CH2PH2)] (37). They found that in the isocyanide complex a negative charge is accumulated on the Cl and N atoms. These two sites may therefore compete for electrophiles however, the product of N attack is thermodynamically favored. 

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