COMPARISON OF ABINITIO, SEMIEMPIRICAL, AND MOLECULAR MECHANICS CALCULATIONS FOR THE CONFORMATIONAL-ANALYSIS OF RING-SYSTEMS

被引:61
作者
FERGUSON, DM [1 ]
GOULD, IR [1 ]
GLAUSER, WA [1 ]
SCHROEDER, S [1 ]
KOLLMAN, PA [1 ]
机构
[1] UNIV CALIF SAN FRANCISCO,DEPT PHARMACEUT CHEM,SAN FRANCISCO,CA 94143
关键词
D O I
10.1002/jcc.540130413
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The potential energy surfaces of four cyclic alkanes have been examined using molecular mechanics, semiempirical, and ab initio methods to determine if they produce mutually consistent results and investigate the source of any errors between the methods. The C5 - C-8 cyclic alkanes were chosen since these structures present a finite set of conformations and transition-state geometries and are still within the computational time and memory limits of the quantum mechanical approaches. We also examined several conformations of 1,2-dideoxyribose to determine the effect of heteroatoms on the results for the 5-membered ring. The molecular mechanics and ab initio calculations are consistent in the relative energies and geometries determined for the conformers of all ring systems. While the semiempirical calculations yielded geometries consistent with the other methods (except for 5-membered rings), the relative energies often deviated substantially. A decomposition analysis of the semiempirical and molecular mechanics energies revealed that the disparities are mainly due to errors in the 1-center energies of the semiempirical calculations. The 2-center bonding and nonbonding energies followed reasonable trends for the conformers. The core-repulsion function, however, is suspected of producing anomalies. A minimum in the attractive Gaussian of this term at 2.1 angstrom for H-H interactions partly explains the propensity of the 5-membered rings to optimize to near planarity (decreasing 1,2-diaxial hydrogen distances to 2.3 angstrom) and the underestimation of the relative energy of the boat structure of cyclohexane.
引用
收藏
页码:525 / 532
页数:8
相关论文
共 51 条
[1]   CONFORMATIONAL-ANALYSIS .130. MM2 - HYDROCARBON FORCE-FIELD UTILIZING V1 AND V2 TORSIONAL TERMS [J].
ALLINGER, NL .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1977, 99 (25) :8127-8134
[2]   CONFORMATIONAL ANALYSIS .10. THE ENERGY OF THE BOAT FORM OF THE CYCLOHEXANE RING [J].
ALLINGER, NL ;
FREIBERG, LA .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1960, 82 (09) :2393-2394
[3]   CONFORMATIONAL ANALYSIS .23. 4-CYCLOHEPTEN-1-ONE SYSTEM [J].
ALLINGER, NL ;
SZKRYBAL.W .
JOURNAL OF ORGANIC CHEMISTRY, 1962, 27 (03) :722-&
[4]  
ALLINGER NL, 1981, QUANT CHEM PROGRAM E, V13, P395
[5]   DETECTION OF A CROWN FAMILY CONFORMATION IN CYCLOOCTANE BY PROTON AND C-13 NUCLEAR MAGNETIC-RESONANCE [J].
ANET, FAL ;
BASUS, VJ .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1973, 95 (13) :4424-4426
[6]  
ANET FAL, 1973, TETRAHEDRON LETT, V50, P5029
[7]  
[Anonymous], 1970, APPROXIMATE MOL ORBI
[8]  
[Anonymous], 1986, AB INITIO MOL ORBITA
[9]  
BARTELS RH, 1972, CNA44 U TEX CTR NUM
[10]  
BEVERIDGE DL, 1991, THEORETICAL BIOCH MO, V1