Chemistry 14D Winter 2010 Exam 2 Page 1

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1 Chemistry 14D Winter 2010 Exam 2 Page 1 1. (2) Circle the best statement of Markovnikov s rule. (a) When X adds to an alkene, the hydrogen of X becomes bonded to the alkene carbon that bears the least number of hydrogen atoms. (b) When X adds to an alkene, the hydrogen of X becomes bonded to the alkene carbon that bears the greatest number of hydrogen atoms. (c) An addition reaction to an alkene always proceeds through the most stable carbocation. (d) Addition of X to an alkene gives the least sterically hindered product. 2. (2) Which of the following is the correct mechanistic rationale for Markovnikov s rule? Circle one: Steric effects Resonance Carbocation stability Leaving group Solvent polarity 3. (5) For each reaction, circle Yes if the reaction follows Markovnikov s rule, and No if it does not. For the reactions that do obey Markovnikov s rule, write the major product in the box. (a) 1. B 3 2. NaO, OO (b) 2 (c) C CC Pt 3 Yes No Yes No Yes No 4. (6) Write the mechanism for the major product of the following reaction. Draw a box around the product. OC 3 Cl 5. (3) By adding, subtracting, or transmuting no more than three atoms of the nucleophile, rewrite the reaction of question 4 so that it is obviously faster. (Transmute = change an atom of one element into an atom of another element, i.e., lead into gold.) Do not include the reaction mechanism. 6. (3) Finish this statement in ten words or less: During steroid biosynthesis, squalene oxide (an epoxide) must be protonated prior to nucleophilic attack by the alkene pi electrons because... Page 1 score =

2 Chemistry 14D Winter 2010 Exam 2 Page 2 7. (2) Which of these carbocation fates are not involved in steroid biosynthesis? Circle all that apply. Rearrangement Capture a nucleophile Be deprotonated to form pi bond All of these are involved 8. (12) Write the mechanism for the major product of the following reaction. Draw a box around the product. OK to use Ph. C CC 3 2 O 2 SO 4 9. (2) The primary explanation for directing effects in electrophilic aromatic substitution reactions is (circle one): Probability Steric effects Arenium ion stability Origin of the electrophile Reaction product stability 10. (2) When a benzene ring bears an atom with a lone pair (i.e., Ph X:), electrophilic aromatic substitution reactions on this benzene ring will usually give significant amounts of which product(s) (circle all that apply)? Ortho Meta Para Cannot determine from the information given 11. (2) When a benzene ring bears an atom with a lone pair (i.e., Ph X:), X is (circle one): EAS activator EAS deactivator Both simultaneously Cannot determine from the information given 12. (2) Circle the letter of the slowest reaction. (a) Benzene reacts with Cl 2 and AlCl 3. (c) Nitrobenzene (PhNO 2 ) reacts with Cl 2 and AlCl 3. (b) Toluene (PhC 3 ) reacts with Cl 2 and AlCl 3. (d) Anisole (PhOC 3 ) reacts with Cl 2 and AlCl 3. Page 2 score =

3 Chemistry 14D Winter 2010 Exam 2 Page (2) Circle the major product of this reaction: 2 Fe (3) Finish this statement in twenty words or less (be very specific): In a Friedel-Crafts alkylation reaction, the role of AlCl 3 is (3) Using anisole (PhOC 3 ) as the starting material plus any other necessary reactants, write an example of the Friedel-Crafts alkylation reaction. Give the major product, but not the mechanism. OC 3 When skin comes in contact with aqueous nitric acid, the skin may be stained yellow. This is due to electrophilic aromatic nitration of the skin s amino acids that have aromatic side chains, such as phenylalanine and tyrosine. Questions refer to this nitration reaction. Aqueous nitric acid contains 2 O, 3 O +, and ONO 2. O Phenylalanine side chain Tyrosine side chain 16. (1) Circle the side chain that undergoes electrophilic aromatic nitration more quickly: Phenylalanine Tyrosine 17. (3) Complete this sentence in twenty words or less: The side chain that I selected is nitrated faster because (11) Write the mechanism for the electrophilic aromatic nitration of the tyrosine side chain by aqueous nitric acid and aqueous sulfuric acid. Draw a box around the product. Label the rate-determining step as rds. O aq. ONO 2 aq. 2 SO 4 Page 3 score =

4 Chemistry 14D Winter 2010 Exam 2 Page (5) Circle the most likely product of this mechanism step: O 2 Draw curved arrows to show how your selection is formed: Finish this statement in twenty words or less (be very specific): This is the most likely product because (2) Which of the following is not a chain reaction? Circle one or more. (a) Reaction of propane with Cl 2 and heat. (c) Reaction of propene with and hydrogen peroxide. (b) Reaction of Cl 2 CF 2 with O 3 and hν. (d) Reaction of propene with B 3 followed by NaO and OO. (e) None of these 21. (6) Circle the most likely product of this mechanism step: C 3 O C 3 O C 3 O C 2 O C 3 C 3 C 3 C 2 C 3 C 3 C 3 C 3 Complete this sentence in ten words or less: This is the most stable radical because... In addition to the radical I circled, the other product of this mechanism step is. 22. (9) Write the mechanism for the following reaction. Draw a box around the product. Cl 2 heat Page 4 score =

5 Chemistry 14D Winter 2010 Exam 2 Page (12) Write the major organic product, best reactant(s), or best starting material in the boxes. Assume reagents above/below the arrows are not in excess unless otherwise specified. Do not include any mechanism details. If no reaction occurs write NR. (a) 2 O 2 (b) NO 2 SO 3 2 SO 4 O (c) 2 O 2 SO 4 (d) 1. O 3 2. (C 3 ) 2 S O O Page 5 score =