Introduction to Molecular Modeling

Introduction to Molecular Modeling - Introduction to...

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Unformatted text preview: Introduction to Molecular Modeling Natalie Chartrand Lab Section 3 October 3, 2007 Acyclic Aliphatic Hydrocarbons Aliphatic compounds: Molecules having hydrocarbon chains that usually contain portions of carbon atoms with four single bonds 1 . Methane Bond length: 1.09 Bond angle: 109.5 Dichloromethane E= -671.9023 C-Cl bond length: 1.74 C-H bond length: 1.11 Cl-C-Cl bond angle: 112.998 Cl-C-H bond angle: 107.941 H-C-H bond angle 112.144 Ethane-Staggered C-C-H bond angle: 110.723 H-C-H bond angle: 108.191 Distance between H atoms: cis: 2.51791 trans: 3.1009 Ethane-Eclipsed E= -670.6617 C-C-H bond angle: 110.043 H-C-H bond angle: 107.855 Note: Ethane, in its staggered conformation, is more stable mainly because the hydrogen atoms are slightly farther apart. Propane C 1-C 2 hydrogen atoms eclipsed: E= -952.5695 C 1-C 2 and C 2-C 3 hydrogen atoms eclipsed: E= -950.9236 Staggered (all hydrogen atoms): E= -953.8936 Note: According to the calculated energy values for the molecules, propane, in which all of the hydrogen atoms are staggered, is the most stable conformer for this substance. Again, this is due to the fact that the hydrogen atoms are slightly farther apart when staggered than they are when eclipsed. Butane Anti: E= -1235.3671 Distance from C 1-C 4 : 3.83718 Anticlinal Eclipsed: E= -1234.3617 Distance from C 1-C 4 : 3.59408 Gauche: E= -1235.0991 Distance from C 1-C 4 : 3.07541 Syn-periplanar: E= -1232.6130 Distance from C 1-C 4 : 2.79952 Note: Based on their energies, the conformers of butane, from most stable to least, are Anti, Gauche, Anticlinal eclipsed, and Syn-periplanar. Chart 1 Relative Energies of Butane Conformations-1236.0-1235.5-1235.0-1234.5-1234.0-1233.5-1233.0-1232.5-1232.0 60 120 180 Angle Between Methane Groups of Adjacent Carbon Atoms Relative Energy Cyclic Aliphatic Hydrocarbons Alicyclic: (aliphatic cyclic) A term indicating that a molecule has one or more rings but lacks the conjugated bonds that characterize an aromatic compound. 1 Cyclopropane E= - 807.6188 C-C-C bond angles: 60 Distance H-H: cis: 2.57442 trans:...
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This note was uploaded on 03/05/2008 for the course CHEM 2500 taught by Professor Dr.paulhayes during the Fall '07 term at University of Lethbridge.

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Introduction to Molecular Modeling - Introduction to...

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