2006_Midterm1_Solutions

2006_Midterm1_Solutions - Name: HUID: Chemistry 17 HOUR...

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Name: HUID: Page 1 of 8 Chemistry 17 HOUR EXAMINATION #1 Answer Key Name: ___________________________ HUID #: __________________________ TF: ______________________________ Section Time (Day/Hour): ___________ Instructions : Please verify that your exam has a total of 7 pages (including this one), and write your name and Harvard ID number on each page. Write your answers in the space provided after each question. Exams written using red pen, or corrected with “white-out” will not be eligible for regrades. If you provide multiple answers for the same question, place a box around the answer to be graded. Otherwise, your first answer (and nothing else) will be graded. Calculators are not permitted; molecular models are allowed. Be sure to manage your time (55 minutes) wisely, taking care to note the point value associated with each problem. Question Point Value Score 1 26 2 20 3 24 4 15 5 15 Total 100
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Name: HUID: Page 2 of 8 Question 1 (26 points). Please use molecular orbital theory to explain the following observations: (a) ( 5 pts) The trajectory of nucleophilic addition to carbonyl compounds is perpendicular to the plane defined by the carbonyl group and at 105 ° to the C-O bond. O R R Nu 105 ° Nucleophiles (HOMO) will add to the π * C-O bond, the LUMO of carbonyl compounds, in a trajectory to maximize orbital overlap. The largest lobe of the π * orbital is located on C and is slightly tilted from 90 ° because there is a node between the carbon and oxygen atoms. CO LUMO: CO π * R R Nu (b) ( 8 pts. ) Enamines undergo protonation at nitrogen or at carbon 2 , but not at carbon 1 . N H 3 C CH 3 H 3 C CH 3 H 3 O + N H 3 C H 3 C CH 3 CH 3 N H 3 C H 3 C CH 3 CH 3 observed not observed enamine 1 2 N H 3 C CH 3 H 3 C CH 3 H observed
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2006_Midterm1_Solutions - Name: HUID: Chemistry 17 HOUR...

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