Non-empirical LCAO-MO-SCF-CI calculations on organic molecules with Gaussian type functions

Csizmadia, Imre G.; Harrison, Malcolm C.; Sutcliffe, Brian T.

doi:10.1007/bf00529348

Cited by 43 publications

(14 citation statements)

References 20 publications

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“…Formamide is essentially computed to be planar, as found in previous small basis set ab initio molecular orbital calculations [41], but cyanamide is predicted to be pyramidal. The geometries of some of the amido anions differ substantially from those of the amines (see Table II), and these differences correlate well with the geometric changes previously found for protonation of the amines to form the ammonium cations [42, 431. Removal of a proton from ammonia produces an increase in the remaining N-H bond lengths, and the H N H angle is decreased to a value slightly smaller than in the isoelectronic water.…”

Section: B Geometriessupporting

confidence: 57%

An ab initio molecular orbital study of the deprotonation of amines

Hopkinson

Lien

1978

Int J of Quantum Chemistry

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AbstractsThe geometries of the amines NHzX and amido anions NHX-, where X = H, CH3, NH2, OH, F. C2H, CHO. and CN have been optimized using ab initio molecular orbital calculations with a 4-31G basis sct. The profiles to rotation about the N-X bonds in CH3NH-, NHzNH-, and HONH-are very similar to those for the isoprotic and isoelectronic neutral compounds CH30H, NHzOH, and HOOH. The amines with unsaturated bonds adjacent to the nitrogen atoms undergo considerable skeletal rearrangement on deprotonation such that most of the negative charge of the anion is on the substituent. The computed order of acidity for the amines NH2X is Xand for the reaction N HX-+ H+ -NH2X the computed energies vary over the range 373-438 kcal/rnol. 1,es g6omEtries des amines NH2X et des amido-anions NHX-ont CtC optirnistes dans des calculs MO ah rnitio avec un jeu de base 4-31G, pour les cas oh X = H, CH3, NH2, OH, F, CzH, CHO, et CN. Les profile\ de rotation autour des liaisons N-X dans CH3NH-, NH2NH-, et HONH-sont trts semblables aux quantitts correspondantes des composts neutres isoprotiques et isotlectroniques CH30H, NH20H, et HOOH. Les arnines avec des liaisons non saturees avec des atomes d'azote cornrne voisins subissent un r6arr:ingement giornktrique considtrable en raison de la dtprotonation, ce qui transfert la plupart de la charge ntgative de I'anion au substituant. L'ordre d'aciditt calcult pour les amines NH2X est X = CN > HCO > F -C2H > O H > NH2 > CH, > H. Pour la rtaction NHX-+ H+ -NHzX lestnergiescal-cu1i.c~ varient dans I'intervalle 373-438 kcal/mol.Die Gcometrien der Arnine NH2X und der Amidoanionen NHX-sind in ah initio-Mo-Bereehnungen niit cineni Basissat, von Typ 4-31G optimisiert worden, fur die Falle wenn X = H, CH3, NH2, OH, F, C2H, CHO, und CN ist. Die Drehungsprofile urn die N-X-Bindungen in CH3NH-, NHzNH-, und HONHsind sehr ahnlich den entsprechenden Profilen fur die isoprotischen und isoelektronischen neutralen Verbindungcn CH3OH. NHr OH, und HOOH. Die Arnine mit nichtgesattigten Bindungen benachbart den Stickstoffatornen erdulden betrichtliche geometrische Umordnungen zufolge der Deprotonierung, was cine c;bcrfiihrung der rneisten negativen Ladung des Anions zum Substituent ergibt. Die berechnete Aciditatsordnung der Amine NH2X ist X = C N > HCO > F = C2H > OH > NH2 > CH3 > H. Fur die Rcaktion NHX-+ H + -NHzX variieren die berechneten Energien irn Interval1 373-438 kcal/rnol.

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Section: B Geometriessupporting

confidence: 57%

An ab initio molecular orbital study of the deprotonation of amines

Hopkinson

Lien

1978

Int J of Quantum Chemistry

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“…We can see from Table VIII that [33]; ARC, Robb and Csizmadia [34]) and experimental (E, Kurland and Wilson [30]). M, Aso, ARC, and E vectors have magnitudes of 3.86, 4.1, 4.15, and 3.71 debye, and directions of 35.9", 38", 45.5", and 39.6" from the Nl-C2 axis.…”

Section: Results and Discussion For Amide And Urea Seriesmentioning

confidence: 92%

“…Both methods place the 2a"(.rr) orbital as the first ionization, and the 7a' orbital as the second ionization. More rigorous ab initio calculations, which estimate the energies of both neutral and ionized states of formamide and also take electron correlation into account, have been applied to the upper two ionizations of Dipole moment vectors for formamide: MIND0/3 (M), ab inirio (AsD,Stenkamp and Davidson [33]; ARC, Robb and Csizmadia[34]) and experimental (E, Kurland and Wilson[30]). M, Aso, ARC, and E vectors have magnitudes of 3.86, 4.1, 4.15, and 3.71 debye, and directions of 35.9", 38", 45.5", and 39.6" from the Nl-C2 axis.…”

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confidence: 99%

Evaluation of MINDO/3 calculations in simple amides, ureas, and heterocycles of biological interest

Defina

Andrews

1980

Int J of Quantum Chemistry

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AbstractsThe performance of the M I N D 0 / 3 method has been evaluated in simple heteroatomic molecules that are representative of several important biological systems. Molecular geometries are accurate to within 0.04 A for bond lengths, and 3" for most bond angles. Dipole moments and charge distributions are estimated satisfactorily, and ionization potentials are predicted to an accuracy of 0.5 eV. The method is less accurate in estimating the ionization of some upper level u orbitals. The overall evaluation shows that MIND0/3 provides a good description of the geometries and electronic properties of the molecules studied

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“…One area leading to computing economy is the developmerWof small Gaussian basis sets, and considerable effort has been expended for their determination. Subminimal bases have been employed by Christoffersen et al [ 11 for use in the floating spherical Gaussian orbital approach [2], and small energy optimized (5s, 2 p ) bases for first-row atoms have been reported by Whitman and Hornback [3] and Robb and Csizmadia [4].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of small Gaussian basis sets forab-initio calculations on biologically active molecules

Graf

Mehler

1981

Int. J. Quantum Chem.

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Abstract(5s, 2 p ) and (7s, 4p) Gaussian basis sets are presented and evaluated for first-and second-row atoms, respectively, appearing in biologically active molecules. The exponents of the valence shell primitives are taken from larger bases, where the valence shell is better represented, in order to avoid the overemphasis on the core, which occurs in small bases when all exponents are optimized. Contraction coefficients are given for constructing double zeta and minimum molecular basis sets. The basis sets are evaluated by applying them to 19 molecules containing first-or second-row atoms.The results indicate that they are competitive with larger bases for the calculation of properties mainly dependent on the valence shell electrons. In particular, proton affinities seem to be quite reliably reproduced so that they can be used for investigations involving reaction or interaction with proton donors.

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Non-empirical LCAO-MO-SCF-CI calculations on organic molecules with Gaussian type functions

Cited by 43 publications

References 20 publications

An ab initio molecular orbital study of the deprotonation of amines

An ab initio molecular orbital study of the deprotonation of amines

Evaluation of MINDO/3 calculations in simple amides, ureas, and heterocycles of biological interest

Evaluation of small Gaussian basis sets forab-initio calculations on biologically active molecules

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