Chem 380.37 Assignment 1

Determine the equilibrium geometries of each of the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ules). Determine the equilibrium geometries of each of the conformers using the MMFF94 Molecular Mechanics force field (see Appendix 3 for instructions on performing molecular mechanics calculations). Record the total energy of each one in kcal/mol. Discuss whether or not the results agree with your qualitative predictions. PART B ( 7 p oints) - E quilibrium G eometry o f B iphenyl a nd S ubstituted B iphenyl What is the equilibrium torsional angle of biphenyl? To find out, first build the biphenyl molecule using Avogadro. biphenyl 2 The torsional angle in question is for rotation about the central C-C bond. In order to build biphenyl, it is helpful to start with pre-built benzene rings available in the Avogadro library. To locate the fragment library, select "Build → Insert → Fragment". Open the aromatics folder, select benzene, and then click "Insert Fragment". At this point a benzene molecule should appear in the display window highlighted in blue. Use the mouse buttons to translate and rotate the molecule into a suitable position to form biphenyl; then insert a second benzene fragment and orient it appropriately. The last step is to use the Drawing Tool to connect the two benzene rings to form biphenyl. To do this, select the Drawing Tool, make sure that the element selected is Carbon, and make sure to click ON the button to "Adjust Hydrogens". Then use the mouse to draw a bond from one benzene ring to the other as shown above in the sketch of biphenyl. Once you have built the biphenyl molecule, perform a calculation to determine its equilibrium geometry using the MMFF94 force field. Measure the torsional (dihedral) angle (use the Measure Tool, ; see Appendix 4 for additional information on measurement). With the torsional angle displayed, repeat the selection of "Extensions → Optimize Geometry" until the torsional angle stops varying – this is the final result. Report the calculated value of the torsional angle of biphenyl. Does the result of your molecular mechanics calcul...
View Full Document

This document was uploaded on 03/04/2014 for the course CHEM 380.37 at Illinois State.

Ask a homework question - tutors are online