Exercise 2 Charge Distribution in Aromatic Compounds. Build a molecule of benzene by clicking the Ring Fragment icon and

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Exercise 2 Charge Distribution In Aromatic Compounds Build A Molecule Of Benzene By Clicking The Ring Fragment Icon And 1 (151.38 KiB) Viewed 57 times

Exercise 2 Charge Distribution in Aromatic Compounds. Build a molecule of benzene by clicking the Ring Fragment icon and choosing the benzene fragment. Click in the View workspace. Minimize at the PM3 level. Save the files as benzene.chk and benzene.cjf. Click Results / Surfaces. Click Cube Actions / New Cube / Total Density / OK and Cube Actions / New Cube / ESP / OK. Be sure Electron Density appears in the Cubes Available window. Click Surface Actions / New Mapped Surface to display the Electron Density on ESP surface. Record your observations. Close everything except the main Control Panel. N Either open the file PYRIDINEPM3.chk or construct the pyridine molecule using the pyridine Ring Fragment. Run a PM3 minimization if needed. Display the Electron Density on ESP surface as above and record your observations. pyridine Describe the differences between the benzene and pyridine charge distribution. What causes this difference? Exercise 3 The Diels-Alder Reaction a,ß-unsaturated carbonyl compounds undergo an exceedingly useful reaction with conjugated dienes known as the Diels-Alder reaction. In this cycloaddition reaction, C-1 and C-4 of the conjugated diene become attached to the doubly- bonded carbons of the unsaturated carbonyl compound to form a six-membered ring. The reaction involves systems with 4īt electrons (diene) and 21 electrons (dienophile), and is therefore a [4+2] cycloaddition. The frontier molecular orbital approach is a good way to understand this reaction. We will look at a simple Diels-Alder reaction involving butadiene and maleic anhydride: 0 + ???