University of Maryland--Baltimore County Chemistry 351L Fall, 1994 Final Exam Part I--Multiple Choice Answer the following questions on the computer op-scan answer sheet provided. 1. After hydration of norbornene you recovered the product norborneol by adding two portions of ether to the acidic reaction mixture. What is the purpose of adding the ether? A) The product has a distribution coefficient greater than one for concentration in ether divided by concentration in aqueous solution so this step separates the product from the reaction reagents. B) The product has a distribution coefficient less than one for concentration in ether divided by concentration in aqueous solution so this step separates the product from the reaction reagents. C) Ether is the solvent for the final step in the hydration reaction. D) It's not really necessary to add the ether; the product can be purified by sublimation. E) The experiment would be too short without this step. 2. Which of the following is not a method by which sodium chloride can be used to advantage for the work-up of the product of an organic reaction? A) to salt out a non-polar product in an extraction of the product into an organic phase from an aqueous phase B) to partially dry an organic phase as a concentrated brine wash C) to break up an emulsion of water with an organic layer less dense than water D) added as a solid to an organic phase as a final drying agent 3. Which product would you expect from the acid-catalyzed addition of water to Refer to figure F09004 A) I B) II C) III D) IV E) V 4. Acid-catalyzed hydration of 2-methyl-1-butene would yield which of the following? A) CH3 | CH2CHCH2CH3 | OH B) CH3 | CH3CCH2CH3 | OH C) CH3 | CH3CHCHCH3 | OH D) CH3 | CH3CHCH2CH2OH E) CH3CH2CHCH2OH | CH3 5. What product would result from the following reaction? Refer to figure F09014 A) I B) II C) III D) IV E) V 6. Which compound listed below would you expect to be the major product of this reaction? CH3 | ethanol CH3CH2CBr + KOH --------> ? | reflux CH3 A) CH3 | CH3CH2COH | CH3 B) CH3 CH3 | | CH3CH2C-O-CCH2CH3 | | CH3 CH3 C) CH3CH2CÍCH2 | CH3 D) CH3CHÍCCH3 | CH3 E) CH2ÍCHCHCH3 | CH3 7. Which alkene would you expect to be the major product of the following dehydration? Refer to figure F08065 A) I B) II C) III D) IV E) V 8. Which of the following alcohols would dehydrate most rapidly when treated with sulfuric acid? A) CH3 | CH3CHCCH3 | | HO CH3 B) CH3 | CH3C--CHCH3 | | OH CH3 C) CH3 | CH3CCH2CH2OH | CH3 D) CH3CH--CHCH3 | | CH3 OH E) CH3CH2CH2CH2OH 9. Which of the following carbocations would NOT be likely to undergo rearrangement? A) CH3CHCHCH3 + | CH3 B) CH3 | CH3CHCCH3 + | CH3 C) CH3 | CH3CCH2CH3 + D) CH3 | CH3CHCH2+ E) CH3 | CH3CCHCH2CH3 |+ CH3 10. An oxygen-containing compound which shows no IR absorption at 1630- 1780 cm-1 or at 3200-3550 cm-1 is likely to be what type of compound? A) An alcohol B) A carboxylic acid C) An ether D) A ketone E) An aldehyde 11. Which reaction is an oxidation? A) RCHO ------> RCO2H B) RCH2OH ------> RCHO C) RCH2OH ------> RCO2H D) More than one of these E) All of these Answer Key: 1. A 4. B 7. C 10. C 2. D 5. C 8. B 11. E 3. D 6. D 9. C Part II--Short Answer Answer the following questions on the short-answer sheet provided. 12. Predict the major organic product of the following reactions. Show regiochemistry and stereochemistry where necessary. 1-methylcyclohexene bicyclo[4.4.0]decan-3-one (1R,2R)-1,2-dideuterio-1-methylcyclopentane and (1S,2S)-1,2-dideuterio-1-methylcyclopentane 1-methylcyclohexene no reaction 13. If the dehydration of cyclohexanol is conducted under reflux rather than with distillation the yield of cyclohexene is much less. Why? Removing the product by distillation pushes equilibrium toward more product. 14. The potential energy diagram is shown below for the catalytic hydrogenation of 2-butene in the presence of platinum catalyst. Draw on the same figure the potential energy diagram for the hydrogenation of 1-butene without a catalyst present. Potential enery curve starts out higher in energy than shown, goes over a transition state that is higher than shown, and finishes at the same energy. 15. Show all of your work in answer to this question. a. Complete and balance the following reaction equation. CH3(CH2)3CH2OH + Cr2O7-2 -----> CH3(CH2)3COOH + Cr+3 ( CH3(CH2)3CH2OH + H2O ------> CH3(CH2)3COOH + 4H+ + 4e ) X 3 ( Cr2O7-2 + 14H+ + 6e ------> 4 Cr+3 + 7H2O ) X 2 3 CH3(CH2)3CH2OH + 2 Cr2O7-2 + 16 H+ ------> 3 CH3(CH2)3COOH + 4 Cr+3 + 11 H2O b. What mass of Cr2O7-2 in the form of the potassium salt is required to oxidize 980 mg of 1-pentanol? (Atomic wts: H-1; C-12; O- 16; K-39; Cr-52) 0.98 X 2 X MW K2Cr2O7 (294 g) = 2.18 g ______ _ 88 g/mol 3 c. If the yield of the oxidation of 980 mg of 1-pentanol is 1.4 g pentanoic acid what is the percent yield of the reaction? 0.98g X M.W. pentanoic acid (102g) = 1.14 g theoretical yield ____ 88 g/mol 1.4/1.14 = 123% yield 16. Show a reasonable mechanism for the oxidation of cyclododecanol to cyclododecanone. __> Cl-OH _> ( (_> H ( _ OH +O-Cl O /\/ \/ /\/ \/) /\/ \// | | | |\H | | \/\ _/ \/\ _/ ^\OH2 \/\ _/ (too hard to do in ASCII) 17. Identify the following compound based on the spectra and other information provided. Ph | C=O | CH2 | CH3 -- * /\o__ H. Mark Perks, Dept. of Chem., UMBC, Baltimore, MD 21228 ~^~^~^~^~ perks@umbc.edu 410 455-2789 These opinions are exclusively my own.