摘要:

AbstractConformational energy calculations using the empiricalMM2 (molecular mechanics II) and semiempirical quantum mechanicalPCILO(perturbative configuration interaction using localized orbitals) methods are reported for various prodine derivatives. These include 3‐demethylprodine, α‐prodine, β‐prodine, the α‐2‐methyl derivative, α‐promedol, the γ‐2,3‐dimethyl derivative, and γ‐isopromedol. The results are consistent with all of the compounds activating the opiate receptor in a phenyl equatorial conformation with optimum activity resulting from a particular orientation of the phenyl and propionoxyl groups. In disagreement with previous limited experimental data, α‐promedol is found to prefer a phenyl equatorial conformer. It is confirmed that, of the two mirror image phenyl equatorial conformers that are preferred for 3‐demethylprodine, the more active prodines antipodes consistently prefer the one in which the phenyl orientation is the opposite (mirror image) of that found in morphine and in the preferred conformer of the morphine‐like (+)‐phenylmorphan. This is a possible molecular basis for the nonmorphine‐like effects that occur with the introduction of a phenylmetahydroxyl into some prodine derivatives. It is also suggested that the less active prodine antipodes, which have a morphine‐like phenyl orientation, may act in a morp

ISSN:0192-8651    

DOI:10.1002/jcc.540050602

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractIn order to provide additional data for the relative lengths of methyl‐CH bond distances in acetyl derivatives, which are difficult to determine accurately by the conventional tools of structural chemistry, the geometries of CH3COH, CH3COF, CH3COCH3, CH3COOH, and CH3CONH2were determined byab initioSCFgradient optimization at the 5‐31G** level and compared with previous 4‐21G results. For acetaldehyde 6‐311G4* calculations were also performed and the correlated methyl‐CH stretching potential energy functions were determined. It is found that the calculated differences between the in‐plane and out‐of‐plane methyl‐CH bonds are practically independent of the computational scheme. The calculated results are in contrast to relative bond lengths obtained by some vibrational overtone spectroscopic studies, but are in perfect agreement with CH bond length differences determined from isolated CH stretching frequencies of partially deuterated compounds. The reliability of the latter, and other spectroscopic data concerning the assignment of the methyl‐CH vibrations are critically analyzed. On the basis of the available evidence we conclude: (1) the methyl groups of the CH3C(O)Xsystems here discussed contain one strong (in‐plane) and two weak (out‐of‐plane) CH bonds; (2) intensities of CH local mode spectra do not provide a reliab

ISSN:0192-8651    

DOI:10.1002/jcc.540050603

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractA numerical procedure is described and tested for the determination of solvent sites in a crystal hydrate from computer simulation results. The method does not require the computation of density distributions.

ISSN:0192-8651    

DOI:10.1002/jcc.540050604

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractPotential energy surface for methyl fluoride dimer has been studied theoretically withab initiomolecular orbital method, using a 4‐31G basis set. Dimer dissociation energies, Mulliken electronic populations, and dipole moments were obtaine

ISSN:0192-8651    

DOI:10.1002/jcc.540050605

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractAnab initioself‐consistent‐field (SCF) algorithm taking into account all the features of the one‐dimensional translational periodicity and the helical symmetry is presented. This algorithm includes the long‐range correction to the Coulomb potential and is designed to calculate the band structure of periodic one‐dimensional polymers (planar or helical). Its efficiency in terms of computing time and numerical accuracy is tested via applications on a (LiH)nchain, polyethylene, and four conformers of poly

ISSN:0192-8651    

DOI:10.1002/jcc.540050606

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractDistance geometry has been used for some years to find conformations of molecules consistent with given bounds on the interatomic distances. A recent extension of the method, called energy embedding, enforces the geometric constraints as before, but also biases the results toward low‐energy structures. Now a significant improvement on energy embedding is presented, which is less dependent on local optimization for satisfying the geometric constraints. Tests on very small systems with well understood energy functions show that the global minimum energy value is often attained, and geometric constraints are always satisfie

ISSN:0192-8651    

DOI:10.1002/jcc.540050607

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractA generalization of the quantum chemical definition of valence of atoms in molecules is suggested. Valence is considered as expectation value of diatomic parts of density operators. It appears as a sum of contributions from occupied orbitals of all atomic pairs that contain the reference atom. This definition is applicable on self‐consistent‐field (SCF) and configuration interaction (CI) level in any atomic orbitals (AO) basis. Its usefulness is demonstrated in an application to special molecules. Photoelectron spectroscopy and reactivity is discussed in this cont

ISSN:0192-8651    

DOI:10.1002/jcc.540050608

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractA previously published scheme of estimating atomic charges in haloalkanes is extended to include olefines, alcohols amines, acids, ethers, and amides. In the conjugated systems the effects of mesomeric transfer of charge are explicitly included. Generally good agreement with the observed dipole moments of these compounds and their substituted derivatives is found. The atomic charges so obtained are compared with those of other semiempirical and quantum‐mechanical calculations for the amide group. The charges so obtained fall within the range of values obtained by these other schemes, supporting the general validity of this approac

ISSN:0192-8651    

DOI:10.1002/jcc.540050609

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractClassical conformational analysis was applied to the study of the variation of heats of formation (HOF) and geometrical parameters of small‐ring propellanes. As expected, the calculatedHOFis the smallest for [4,4,4] propellane I and the largest for [2,2,2]propellane X. In spite of the different trends exhibited by the strain energy components, the calculatedHOFvalues may be reproduced within a simple additivity scheme. The calculated bridgehead–bridgehead bond length is the longest for [2,2,2]propellane (1.655 Å), lowers with increasing molecular size, and is equal to 1.558 Å for [4,4,4]propellane. In agreement with experimental findings the latter value is significantly larger than the standard value of 1.54 Å typical for unstrained hydrocarbons. Other calculated geometrical parameters as well asHOFvalues cannot be compared with experimental and/or theoretical results since there is a lack of reliable experimental data. Surprisingly, [2,2,2]propellane was found to be more flexible than the less strained bicyclo[2,2,2]

ISSN:0192-8651    

DOI:10.1002/jcc.540050610

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractAccurate vibration–rotation eigenvaluesEvJare sought for very high levels (up to dissociation) of a diatomic potential. The method used is the recent “eigenvalue equation” method [Kobeissi et al.,J. Comput. Chem.,4, 218 (1983)] which dissociates the determination of the eigenvalue from that of the eigenfunction. A new mathematical formulation for anynumericalpotential is presented, which reduces the problem to the use of a single recurrent formula. A numerical application to the model potential used by Cashion [J. Chem. Phys.,39, 1872 (1963)], up tov= 23, gives results equal to the exact eigenvalues to approximately 10−14cm−1. Another application to the model potential used by Johnson [J. Chem. Phys.,67, 4086 (1977)], up tov= 60, gives simila

ISSN:0192-8651    

DOI:10.1002/jcc.540050611

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY