Some difficulties encountered with AM1 and PM3 calculations

被引:28
作者
Anh, NT [1 ]
Frison, G
Solladié-Cavallo, A
Metzner, P
机构
[1] Ecole Polytech, CNRS, DCMR, Lab Mecanismes React, F-91128 Palaiseau, France
[2] EHICS, Lab Stereochim Organomet, F-67008 Strasbourg, France
[3] Univ Caen, ISMRA, Lab Chim Mol & Thioorgan, F-14050 Caen, France
关键词
D O I
10.1016/S0040-4020(98)00773-X
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
AM1 and PM3 underestimate frontier intel actions with respect to steric repulsions. Therefore, if two structures differ by (similar to)1 kcal/mol, their calculated ordering is unreliable. Activation energies tend to increase with substitution, regardless of electronic effects. Atomic charges are sometimes unrealistic tin enolates, the negative charge is larger on C than on O). At van der Waals distances, acid-base and coulombic interactions can prevail over steric repulsions. At all distances, basicities are overestimated and nucleophilicities underestimated. This may lead to anomalous ion-molecule and transition structures in gas phase reactions. Transition structures are tighter than in ab initio calculations. Optimisations may give chemically unreasonable structures. Minimum energy paths are then difficult to obtain. Usually, but nor systematically, PM3 gives more reliable structures and AM1 more realistic energies. (C) 1998 Elsevier Science Ltd. Ail rights reserved.
引用
收藏
页码:12841 / 12852
页数:12
相关论文
共 60 条
[1]  
AAKEROY CB, 1993, J MOL STRUCT, V281, P259
[2]  
ANH NT, 1994, NEW J CHEM, V18, P473
[3]  
ANH NT, 1995, ORBITALES FRONTIERES, P170
[4]   Application of SQMFF to transition states: Thermal decomposition of methylazide and ethylazide [J].
Arenas, JF ;
Otero, JC ;
SanchezGalvez, A ;
Soto, J .
JOURNAL OF MOLECULAR STRUCTURE, 1997, 410 :451-455
[5]  
BADDELEY G, 1973, TETRAHEDRON LETT, P1645
[6]  
BAJ S, 1994, J MOL STRUC-THEOCHEM, V112, P67, DOI 10.1016/0166-1280(94)80204-1
[7]   THEORETICAL INVESTIGATION OF THE RELATIVE STABILITIES OF XSSX AND X(2)SS ISOMERS (X=F, CL, H, AND CH3) [J].
BICKELHAUPT, FM ;
SOLA, M ;
SCHLEYER, PV .
JOURNAL OF COMPUTATIONAL CHEMISTRY, 1995, 16 (04) :465-477
[8]   DICHOTOMY BETWEEN CYCLOADDITION TRANSITION-STATES CALCULATED BY SEMIEMPIRICAL AND AB-INITIO TECHNIQUES [J].
CARAMELLA, P ;
HOUK, KN ;
DOMELSMITH, LN .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1977, 99 (13) :4511-4514
[9]   1,3-dipolar cycloaddition of diazomethane to chiral azlactones. Experimental and theoretical studies [J].
Cativiela, C ;
DiazdeVillegas, M ;
Garcia, JI ;
Jimenez, AI .
TETRAHEDRON, 1997, 53 (12) :4479-4486
[10]   Computational study of the addition of molecular oxygen to benzene [J].
Cheikh, F ;
Boucekkine, A ;
Cartier, A .
JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM, 1997, 397 :13-20