Chemistry 14D Winter 2010 Exam 2A Page 1

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1 Chemistry 14D Winter 2010 Exam 2A Page 1 1. (6) Write the major organic product, best reactant(s) or best starting material in the boxes. Assume reagents above/below the arrows are in excess unless otherwise specified. Do not include any mechanism details. If no reaction occurs write NR. (a) H (b) 2 N 2, Fe 3 Questions 2 4 refer to this reaction: CH 3 H CH 3 + CH 3 2. (1) In the space above circle the major product of this reaction. 3. (5) Write the mechanism for the formation of the major product you selected. Label the ratedetermining step with rds. 4. (3) By adding, subtracting or otherwise changing at most six atoms of the nucleophile, rewrite the reaction (including the major product) so that it is obviously faster. 5. (6) Complete this explanation by adding no more than thirty words: My new reaction of question 4 is faster because... Page 1 score =

2 Chemistry 14D Winter 2010 Exam 2A Page 2 6. (7) Circle the major product of the following reaction, and write a mechanism for its formation. HF + H 7. (10) Write structures for missing reactants A-E in the boxes. Assume all reactants above and below the arrows are present in excess. A (C 9 H 12 ) B hν NaCH 3 CH 3 H C (C 9 H 8 ) D H 2 E (C 9 H 10, a ketone) A = D = B = E = C = 8. (8) Vladimir Markovnikov s doctoral dissertation, published in 1869, was the basis for what is now called Markovnikov s Rule. Markovnikov s studies included the reactions of alkenes with aqueous bromine. An example reaction is shown below. CH 3 (a) Write the structures of two nucleophiles present in this reaction s mechanism: 2 H 2 CH 3 H (b) Write the structures of two electrophiles present in this reaction s mechanism: Page 2 score =

3 Chemistry 14D Winter 2010 Exam 2A Page 3 9. (11) Write the mechanism for the following reaction. Label the rate-determining step as rds. AlCl 3 Cl benzene Questions refer to this reaction of resorcinol (1,3-dihydroxybenzene): H H S 3 H 2 S (3) In the space above, write the major product. 11. (2) If one of the H groups of resorcinol is changed to a hydrogen atom, the reaction with S 3 and H 2 S 4 becomes (circle one): 12. (2) If one of the H groups of resorcinol is changed to a methyl group, the reaction with S 3 and H 2 S 4 becomes (circle one): 13. (2) If one of the H groups of resorcinol is changed to a nitro group, the reaction with S 3 and H 2 S 4 becomes (circle one): Page 3 score =

4 Chemistry 14D Winter 2010 Exam 2A Page (4) Back in the day when the instructor of this course was a professor at another southern California university, an undergraduate student in his research lab discovered the following electrophilic aromatic substitution reaction: NaN 3, TiCl 4 CH 2 Cl 2 Draw the structure of the electrophile that attacks the aromatic ring. Include all lone pairs and formal charges for this electrophile. N (4) The reaction of aniline with NaN 2 and aqueous HCl gives the phenyl diazonium cation and not an electrophilic aromatic substitution product: NH 2 NaN 2 aq. HCl N N or NH 3 Aniline Phenyl diazonium cation EAS product Major product Not formed Complete this explanation by adding no more than twenty words: The phenyl diazonium cation is the major product of this reaction because... N 16. (6) Write a mechanism: Cl 2, heat Cl Page 4 score =

5 Chemistry 14D Winter 2010 Exam 2A Page 5 Questions 17 and 18 refer to the reaction of superoxide with a portion of DNA, shown below. The wavy lines mean molecule beyond this point unimportant. H b NH N H c H a 17. (4) In the space above write the curved arrows and mechanism step product derived from the reaction of superoxide with H a. 18. (7) Complete this statement by adding no more than thirty words (be very specific): Superoxide might abstract H b instead of H c because... (Hint: not due to steric hindrance.) 19. (9) Each of the following mechanism steps may be unlikely to occur as shown. Provide a one-sentence explanation of the error, or rewrite the mechanism step so it is correct. r, if the mechanism step is correct, write ok. (a) H CH 2 + H (b) (c) 2 Page 5 score =