PracExam2Fall2010

PracExam2Fall2010 - Chem 103 Practice Midterm 2 Prof. Chris...

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Chem 103 Practice Midterm 2 Prof. Chris Chang Fall 2010 Version A Name ____________________________________ SID ____________________________________ Signature ____________________________________ Problem 1: ____________ (52 pts) Problem 2: ____________ (56 pts) Problem 3: ____________ (40 pts) Problem 4: ____________ (28 pts) Problem 5: ____________ (26 pts) Problem 6: ____________ (48 pts) Total: ____________ (250 pts)
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1) MO Theory . Prof Ruma Banerjee from University of Michigan gave a seminar here at Berkeley a few weeks ago and spoke on Vitamin B12, which is a Co-dependent molecule essential for life. An inactive form of the enzyme is the cyanide (CN - ) adduct, which needs to be converted to an active form by electron transfer. a) Here is the cobalamin cofactor for B12 without any axial ligands. Assuming all four nitrogens are equivalent in terms of crystal field shape, draw the crystal field, give the oxidation state, and fill in the d electrons for these two forms: [cobalamin] 2+ cobalamin 2+ N N N N Co b) Draw the MO for CN - and fill in its electrons. Please label and draw the orbitals.
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Using a) and b), construct a partial MO diagram for the complex between [cobalamin] 2+ and CN - . Fill in the electrons, and predict whether CN - is bound in a bent or linear fashion. Please label and draw the orbitals. d) Give the total electron count for this active site in c) with the cyanide bound. Is it capable of acting as an electrophile, nucleophile, or radical-based oxidizing agent? Please give a brief reasoning.
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PracExam2Fall2010 - Chem 103 Practice Midterm 2 Prof. Chris...

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