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<p>ORGANIC CHEMISTRY FALL 2017 LANEY COLLEGE CHEM 12A (L1/L1L) INSTRUCTOR: STEPHEN CORLETT EXAM 3 PRACTICE Key Page 1 of 6 1. Which of the two alkenes has the greater heat of combustion (10 points) 2-methyl-1-pentene 2-methyl-2-pentene? -less or + - higher E - greater vs DH less substituted more greater 2. For the following substitution reactions show the product (or products). Indicate whether the reaction proceeds by the Sn1 or Sn2 mechanism. (Be very clear about any stereochemistry outcomes) (10 points) 40 CH3 a. H2O major NaCN CM Br b. CN DMSO only 3. For the following elimination reactions show the product (or products). Be very clear about any stereochemistry outcomes). (10 points) CI Hofmann product t-BuOK a. I product major NaOEt b. (2) CI E2 H only 4 CH3</p><p>ORGANIC CHEMISTRY FALL 2017 LANEY COLLEGE CHEM 12A (L1/L1L) INSTRUCTOR: STEPHEN CORLETT EXAM 3 PRACTICE Page 2 of 6 4. Name the following compound. Assign stereochemistry where appropriate. (10 points) chain 2 3 4 4 (2)-3 -4, pent - 2- 5. Consider the following reaction: (50 points) OTs NaSH SH DMSO a. Draw the mechanism for this reaction (electron pushing). b. Show the rate equation for this reaction? C. What would happen to the rate if the solvent is changed from DMSO to ethanol? d. Explain why there is no E2 reaction observed in this case. e. Draw an energy diagram for this reaction. f. Draw the transition state for this reaction. UTS + SH + a: b. Rate = k [ OSH] C. the rate would increase dramatically 1000 - d. OSM is a superb but a very weak base, no E2 reaction - CH3 TS S e. Tso SH R P Reaction</p><p>ORGANIC CHEMISTRY FALL 2017 LANEY COLLEGE CHEM 12A (L1/L1L) INSTRUCTOR: STEPHEN CORLETT EXAM 3 PRACTICE Page 3 of 6 6. Consider the following series of alkenes. (30 points) a. Rank each of them from most stable (1) to least stable (4). b. Name each alkene (use E/Z notation if necessary) C. Predict which alkene will have the most exothermic heat of hydrogenation (hint: remember, hydrogenation is alkene +H2 alkane) no specified Rank 3 2 4 2 Name - 7. Explain why fluoride is a better nucleophile in DMSO than in ethanol. (10 points) 8. Show how to accomplish all of the following transformations, i.e., fill in the reagents over each arrow. (The problem continues on the next page) (85 points) MBr, NaSH or OH Br SH PBr, NaH OCH3 OTs CN Na o o</p><p>ORGANIC CHEMISTRY FALL 2017 LANEY COLLEGE CHEM 12A (L1/L1L) INSTRUCTOR: STEPHEN CORLETT EXAM 3 PRACTICE Page 4 of 6 8. Cont'd HBr Br OH H2SO4 OTs tooko 9. One of Nature's biochemical mechanisms of dealing with toxic substances, if it has an alcohol functional group (ROH), is to convert it to the B-glucuronide shown below. (30 points) a. What is the reaction mechanism for this transformation? b. What makes the -OUPD group a good leaving group? C. Show the mechanism with electron pushing (note any proton transfers). OH OH o o ROH HO o HO OR + HOUDP HO HO HO HO OUDP B-glucuronide appear to be inverted so SN 2 H N (there is a proten N HO OH 04 H -OUDP - a good leaving group 40 product 11 40 - P - this + has so :- makes good L.G.</p><p>ORGANIC CHEMISTRY FALL 2017 LANEY COLLEGE CHEM 12A (L1/L1L) INSTRUCTOR: STEPHEN CORLETT EXAM 3 PRACTICE Page 5 of 6 10. Consider the table (next page) regarding the Sn2 reaction of select nucleophiles from Group 6A and 7A with methyl iodide Note that this question requires complete explanations for each part (not just one or two word answers) (50 points) a. Which data in the table indicate the trend in nucleophile strength for Group 6A elements - which one is the "stronger" nucleophile? Explain your answer. the rate constants the larger the the faster the reaction - this how a is ranked in terms of is a times b. For the Group 7A nucleophiles, given the trend in the of the conjugate acid, is acidity a factor in the acidity trand would suggest your that FO than predicting how strong the nucleophile is? Explain answer. should be a than since is by definition a base. So in this series the acidity alone doesn' account for the observed trend, C. What effect would switching the solvent of the reaction to DMSO have on the rate of reaction of the nucleophiles in Group 7A with methyl iodide? Explain your answer. changing to an the receives less due to lack of the most concentrated change is using So the trend reverses - FO is is weakest Na d. Where would the nucleophile PhSe be placed in the Table? Explain your answer. would be an entry above in the table and would be greater than 1.1. is actually below sulfur in the periodic table, so the trend would be as w/ the 7A element ( in CH3 e. For the "nothing" reaction in the table - the reaction of methyl iodide with iodide - how would you measure the rate constant for the reaction if "nothing" seems to happen (note the leaving group in this case). Explain your answer. CM3-I + -I + I "a a nothing reaction" as can tell any thing so how to measure Use a of iodine Follow the rate to form 131 50% mixture + I K=1</p>