Molecular mechanics (MM3) calculations on aldehydes and ketones

Allinger, Norman L.; Chen, Kuohsiang; Rahman, Mita; Pathiaseril, Ahammadunny

doi:10.1021/ja00012a020

Cited by 88 publications

(45 citation statements)

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“…Popular force fields, such as MM3 [3][4][5][6][7][8][9][10][11][12][13], AMBER [14][15], and CHARMM [16], have been designed mainly to study biologically interesting molecules. The COMPASS force field, on the other hand, has been specifically designed for material science applications.…”

Section: Introductionmentioning

confidence: 99%

Molecular Modeling of Energetic Materials: The Parameterization and Validation of Nitrate Esters in the COMPASS Force Field

Bunte¹,

Sun²

2000

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To investigate the mechanical and other condensed phase properties of energetic materials using atomistic simulation techniques, the COMPASS force field has been expanded to include high-energy nitro functional groups. This report presents the parameterization and validation of COMPASS for nitrate esters (-ON0 2 ). The functional forms of this force field are of the consistent force field type. The parameters were derived with an emphasis on the nonbonded parameters, which include a Lennard-Jones 9-6 function for the van der Waals (vdW) term and a Coulombic term for an electrostatic interaction. To validate the force field, molecular mechanics calculations and molecular dynamics simulations have been made on a variety of molecules containing the nitrate ester functionality. Using this force field, excellent agreement has been obtained between the calculated and experimental values for molecular structures, vibrational frequencies, liquid densities, heats of vaporization, crystal structure, mechanical properties and lattice energy.n Acknowledgments

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Section: Introductionmentioning

confidence: 99%

Molecular Modeling of Energetic Materials: The Parameterization and Validation of Nitrate Esters in the COMPASS Force Field

Bunte¹,

Sun²

2000

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“…11 Even though the increase in the s character of the C=O bond may contribute to the increase in C=O stretching frequency, it is only a minor contribution. 12 The actual phenomenon is more physical than chemical. The C=O stretching and O-C and C-C stretchings act analogously to the pendulums connected to a common point.…”

Section: Resultsmentioning

confidence: 99%

Molecular mechanics (MM3) study of the lactones ofendo-bicyclo[2.2.2]oct-5-ene-2-carboxylic acid

Kulkarni

Allinger

1999

J. Phys. Org. Chem.

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endo-Bicyclo[2.2.2]oct-5-ene-2-carboxylic acid, in acidic solution, cyclizes to give a mixture of three isomeric lactones. These three isomers have different stabilities and are partly interconvertible, but their simultaneous decomposition makes the experimental study of these equilibria difficult. In the present work, these three lactones were studied using MM3. The relationship between the O-C(O)-C bond angles and the C=O stretching frequencies of these compounds was investigated. Based partly on the thermodynamic data calculated by MM3, the mechanism of the interconversion of the three lactones was proposed.

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“…In the diequatorial dimethyl compound, both methyl groups are almost eclipsed with the adjacent carbonyl, each dihedral angle being 6". This type of eclipsed conformation is energetically favored over the anti(axia1-like) conformation in 2-butanone (9).…”

mentioning

confidence: 94%

“…Unfortunately the "rigidity" of the ketone derivative, cyclohexanone, is much less pronounced. The chair conformation of this ketone is only 3 kcal/mol more stable than its boat forms (8,9). Consequently, the involvement of such less stable species in reaction pathways is of concern, though difficult to assess.…”

mentioning

confidence: 99%

An X-ray and conformational study of 5,7-dihydro-1,11-dimethyl-6H-dibenzo[a,c]cyclohepten-6-one and its methyl derivatives

Fraser¹,

Bensimon²,

Kong³

et al. 1993

Can. J. Chem.

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. Can. J. Chem. 71, 685 (1993). The crystal structures for the title compound 1 and its a-methyl derivatives 2-4 have been determined. Molecular mechanics calculations of the conformation of minimum energy for 1, 3, and 4 correspond closely to the symmetric structures observed in the crystal. For 2, rotation at the CO--CH, bond by 24" produced an asymmetric conformation matching that seen in the solid state. The calculated changes in energy as a function of the torsional angle for 1 and 2 were compared with those for cyclohexanone and the axial conformer of the a-methyl derivative. The energy requirements for conformational change in the seven-membered ring were significantly greater than for the cyclohexane analogue. The calculated energy differences between diastereomeric methyl derivatives 2-4, 6, and 7 were in agreement with epimerization experiments. The distance of closest approach observed between a proton of the axial methyls of 2 and 3 and the distal benzene ring is smaller than expected on the basis of van der Waals' radii.ROBERT R. FRASER, CORINNE BENSIMON, FANZUO KONG et XINFU WU. Can. J. Chem. 71, 685 (1993). On a determint les structures cristallines du compost 1 mentionnt dans le titre et de ses dCrivCs a-mtthyles, 2-4. Des calculs de mCcanique molCculaire de la conformation d'knergie minimale des composts 1, 3 et 4 correspondent bien aux structures symCtriques observtes dans les cristaux. Pour le compost 2, la rotation de 24" autour de la liaison CO--CH, provoque une conformation asymCtrique qui correspond a celle observCe 5 I'Ctat solide. On a cornpark les changements d'tnergie en fonction de I'angle de torsion qui ont CtC calculCs pour les composCs 1 et 2 avec ceux de la cyclohexanone et du conformkre axial de son dCrivC a-mCthylt. L'tnergie requise pour effectuer le changement conformationnel dans le cycle 5 sept chainons est beaucoup plus grand que celui nCcessaire avec I'analogue de la sene cyclohexanique. Les differences d'Cnergie calcultes entre les dtrivts mCthylCs diastCrCoisom&res 2-4, 6 et 7 sont en accord avec ceux de donnks d'CpimCrisation. La distance la plus courte observke entre un proton des groupes mCthyles axiaux des composCs 2 et 3 et le noyau benztnique distal est plus courte que celle attendue sur la base des rayons de van der Waals.[Traduit par la redaction]The bridged biaryl ketone, 5,7-dihydro-1,ll-dimethylL6H-dibenzo[a,c]cyclohepten-6-one, 1, is a chiral derivative of biphenyl whose barrier to racemization was found to be 39 kcal/mol (1, 2). A C2 axis passes through the central ring of 1 and along the C--0 bond of the carbonyl group. As a consequence there are two possible orientations a to the carbonyl, either "axial" or "equatorial" on the basis of their similarity to the geometry at the a positions of cyclohexanone (see Fig. 1). The ring possesses a single rigid conformation, as indicated by molecular models and supported by its proton nrnr spectra (2). We previously made use of 1 and its a-methyl derivatives in three separate studies of stereoselective reactions of t...

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Molecular mechanics (MM3) calculations on aldehydes and ketones

Cited by 88 publications

References 0 publications

Molecular Modeling of Energetic Materials: The Parameterization and Validation of Nitrate Esters in the COMPASS Force Field

Molecular Modeling of Energetic Materials: The Parameterization and Validation of Nitrate Esters in the COMPASS Force Field

Molecular mechanics (MM3) study of the lactones ofendo-bicyclo[2.2.2]oct-5-ene-2-carboxylic acid

An X-ray and conformational study of 5,7-dihydro-1,11-dimethyl-6H-dibenzo[a,c]cyclohepten-6-one and its methyl derivatives

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