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Unformatted text preview: Chemistry 14D Fall 2007 Final Part A Page 1 For any question on Part A and Part B of this exam worth three or more points, you have two choices: answer the question as written or you may write and circle the phrase “one point”. If you write “one point” you will receive one point (and only one point) of credit for the question. “One point” overrides anything you have written for that question, regardless of its accuracy. Example: (10) Briefly explain everything about organic chemistry.
One point O O O P O O O Acyl phosphates such as acetoacetyl phosphate are common intermediates in biochemical reactions involving addition or substitution at a carbonyl group. Questions 1-4 explore the chemistry of these molecules. Acetoacetyl phosphate 1. (9) Name and illustrate the three common carbonyl reaction mechanism steps (fates) commonly found in carbonyl reaction mechanisms. Use acetoacetyl phosphate, HO-, water and H3O+ as the o n l y reactants in each case. If the fate can proceed more than one way, illustrate only the most likely pathway. Include curved arrows. Name of fate #1: ___________________________
O O O P O O O Illustration: Name of fate #2: ___________________________
O O O P O O O Illustration: Name of fate #3: ___________________________
O O O P O O O Illustration: 2. (9) Acyl phosphates are highly susceptible to nucleophilic attack by water. Write the product of the following reaction in the box, plus the corresponding mechanism.
O O H2O P R O O O Mechanism: Chemistry 14D Fall 2007 Final Part A Page 2 We can imagine that an acyl phosphate assists the coupling of an amino acid such as glycine (H2NCH2COOH) to the C-terminus of existing protein chain to form an amide (reaction A). This process is faster than replacement of one of the protein’s existing amino acids by a new glycine (reaction B). The questions on this page concern these two reactions. Reaction A (the faster reaction):
O O P O Protein O O + H2N O N H O OH O OH + O O P O O Extended protein Reaction B (the slower reaction):
O CH2OH OH OH N H O + H2N O N H O O OH + CH2OH OH H2N O 3. (8) Give conceptually rich reasons why reaction A is faster than reaction B. Reason #1 (twenty words or less): Reason #2 (twenty words or less): 4. (6) Reaction A is further assisted by a Mg2+ ion that bridges the carbonyl and phosphate oxygens. Briefly explain (thirty words or less) how this cation accelerates the reaction.
Mg O O P O O O Chemistry 14D
5. Fall 2007 Final Part A Page 3 (12) Each mechanism step shown below is either ok as written, highly improbable, or just plain impossible. If it is not ok, provide a brief explanation why it is improbable/impossible. If it is ok as written write “ok.” Missing curved arrows or reaction products are not part of the improbability or impossibility.
OCH3 H2O O OCH3 OH2 Explanation (ten words or less): O (b)
NH2 H2O OH NH2 Explanation (ten words or less): O (c)
OH H2SO4 O OH2 Explanation (ten words or less): O OCH3 O (d) Explanation (ten words or less): Chemistry 14D
6. Fall 2007 Final Part A Page 4 (9) Write the organic product(s) in the boxes. If more than one organic product is formed, indicate which product is major. Assume reagents above/below the arrows are in excess. Be sure to indicate stereochemistry if relevant. If no reaction occurs, write “NR.” Do not include any mechanism details. (a) O NaOCH3 Cl CH3OH (b) O 1. H2C=CHCH2MgBr OCH3 2. H3O+ (c)
(CH3)2N O O 1. LiAlH4 H 2. H3O+ 7. (10) Provide a mechanism.
O O H2SO4 CH3OH Ph O Ph O OCH3 Chemistry 14D
8. (6) Provide a mechanism. Fall 2007
O KOH OCH3 CH3OH Final Part A
O Page 5 Ph Ph O 9. (4) Complete this sentence in fifteen words or less: In the previous question, the reaction product is PhCO2- and not PhCOOH because... 10. (10) Using fifteen words or less in each case, define or briefly discuss each term relating to the molecular basis for drug action. (a) Enzyme: (b) Suicide inhibitor: (c) DNA intercalator: (d) Prodrug: (e) Sulfa drug: Chemistry 14D
O Fall 2007 Final Part A
O Page 6
O Questions 11-14 on this page refer to this reaction: O NaOCH3, CH3OH N N or N 11. (1) Circle the major product of this reaction. 12. (6) Give two brief (fifteen words or less), obviously different, and very specific reasons for your choice. Reason #1: Reason #2: 13. (8) Write the mechanism for the major product. 14. (1) What is the name of this reaction? 15. (1) Draw an enamine that has exactly six carbons. (No limit on any other atoms.) ...
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