Computational Chemistry

carbonyl groups and electrophilic C/C bonds, radical addition to alkenes, aldol condensations, and various intramolecular reacti ...

3.3.3 To Calculate the Geometries and Energies of Very Large Molecules, Usually Polymeric Biomolecules (Proteins and Nucleic Aci ...

in particular modelling is often done not on an isolated molecule but on a molecule and its environment of solvent and ions) may ...

4 and so was able to undergo Wolff rearrangement ring contraction to the ketene precursor of 4. A remarkable (and apparently sti ...

This survey suggests that: For common organic molecules the Merck Molecular Force Field is nearly as good as the ab initio MP2(f ...

Table 3.3 Error in MMFF molecular mechanics and MP2(fc)/6–31G* bond lengths and angles (From Fig. 3.13 ). Errors are given as MM ...

Table 3.3 (continued) C–H Bond length errors, r-r exp ̊(A ) Bond angle errors, a- aexp O–H, N–H, S–H C–C C–O, N, F, Cl, S Angles ...

methods give good geometries, but while these molecular mechanics calculations all take effectively about one second, MP2 geomet ...

angle of 180. For those dihedrals not involving OO or SS bonds, (an admittedly small selection), the MMFF errors are only ca. 1 ...

the ZPEs used for such corrections are usually obtained from an ab initio or DFT calculation. 3.Infrared spectra. The ability to ...

functional or semiempirical), since frequencies must be calculated using the same method used for the geometry optimization (Sec ...

which MM is oblivious. MM cannot provide information about the shapes and energies of molecular orbitals nor about related pheno ...

alter it slightly by bond rotation and reoptimize; a transition state should slide down toward a nearby minimum (e.g. eclipsed e ...

as being more reliable than thein vacuoones. Solvent effects are discussed in Chapter 8 Section 8.1. 6.Lack of caution about com ...

energies of 0/–13 kJ mol–1, but the experimental value is ca. 0/44 kJ mol–1, i.e. H 2 C¼C(OH)CH 3 is much the higher-energy mole ...

giving actual numbers to the constants in the forcefield constitutes parameterizing the field. An example is given of the devisi ...

MM history: (a) References 1. (b) Engler EM, Andose JD, Schleyer PvR (1973) J Am Chem Soc 95:8005 and references therein. (c) M ...

The Merck force field (ref. [18]) often gives geometries that are satisfactory for energy calculations (i.e. for single-point e ...

Easier Questions What is the basic idea behind molecular mechanics? What is a forcefield? What are the two basic approaches to ...

What factor(s) might cause an electronic structure calculation (e.g. ab initio or DFT) to give geometries or relative energies ...