2005 exam 1 - Chemistry 14C Fall 2005 Exam 1 Page 1 The...

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Chemistry 14C Fall 2005 Exam 1 Page 1 The questions on page 1 – 4 of this exam refer to rhizoxin whose structure can be found on the last page of this exam. 1. (6) Provide numbers concerning the structure of rhizoxin. (a) Total number of lone pairs on all oxygen atoms: ________ (Hint: It is > 3) (b) Total number of lone pairs on all carbon atoms: ________ (c) Number of sp 2 carbons: ________ 2. (2) The best guess for the C-O-C bond angle of the R-O-CH 3 portion of rhizoxin is (circle one): 80 o 85 o 90 o 95 o 100 o 105 o 109.5 o 115 o 120 o 125 o 3. (2) Circle the two atoms that comprise the most polar bond of rhizoxin: Br C Cl F H I N O P S 4. (6) Draw in the boxes two additional, significant resonance contributors for the oxazole (five-membered ring) of rhizoxin. Include all lone pairs. N O R H 3 C Oxazole 5. (4) Draw the resonance hybrid for the oxazole ring of rhizoxin. Include all lone pairs and formal charges. 6. (3) Complete this sentence in twenty words or less: The resonance hybrid is an important structure because. ..
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Chemistry 14C Fall 2005 Exam 1 Page 2 7. (6) Define: (a) Strain: (b) Torsional strain: 8. (2) Circle the fragment of rhizoxin that has the most ring strain. N O CH 3 O CH 3 HO O O O O 9. (4) By adding, subtracting or otherwise changing at most three atoms, redraw your choice from the previous question so that it obviously has less strain .
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2005 exam 1 - Chemistry 14C Fall 2005 Exam 1 Page 1 The...

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