Organic Chemistry II Exam Questions

Written Assignment #4

This assignment is worth a possible total of 100 points. Place your answer in the space provided. Remember that in the problems you must show ALL your work in writing in order to receive full credit for the answers in Part III. Read the “Guidelines” [course syllabus] for further information on what is needed to show your work.

No late papers are accepted except by previous arrangement with the instructor.

PART I – True/False – Circle your response. ( 4 pts each , 20 pts total)

1. Polymerization of alkenes are addition reactions and can have a free-radical or an ionic mechanism. True False

2. Unimolecular elimination reactions, E1, occur with a one-step mechanism, and are very dependent on the stereochemistry of the transition state. True False

3. In some cases, elimination can be made more favorable over substitution by using a bulky base such as diisopropylamine. True False

4. For both E1 and E2 mechanisms, a strongly polar or ionizing solvent is needed.

True False

5. Acid-catalyzed hydration of alkenes involves the formation of a carbocation.

True False

PAR T II – Multiple Choice – Circle your response. ( 6 pts each, 18 pts total)

Note that some questions may require more than one choice to be a complete response.

1. )Which of the following is NOT considered (or called) an electrophilic addition:

(a) oxymercuration-demurcuration

(b) polymerization

(c) ozonolysis

(d) olefin metathesis

2.) For a compound with the molecular formula of C4H6OCl2, the following are possible combinations of unsaturation: Note: Only ONE answer here! (Section 7-3)

(a) two double bonds

(b) one double bond and one ring

(c) one double bond and one triple bond

(d) one double bond or one ring but not both

3.) What would be the most likely (prevalent) product, according to Markovnikov’s rule, in acidic conditions? Note: only ONE answer here (Section 8.3)

PART III – Written Response (42 pts total)

This section requires that you SHOW YOUR WORK clearly and legibly in order to be eligible for full credit for each question. Otherwise, you will not receive full credit, even though you have the correct answer, numerically speaking!!!!! [See the “Guidelines” in the course syllabus.]

1.) (6 pts) Draw a valid (following Lewis structure rules also!) structure for (E)-2-chloro-4ethyl-2-hexene. Explain what the “E” designation refers to.

2.) (16 pts) Consider the following two reactions with 1,2-dimethylcyclohexene. Draw the product or products expected, indicate the stereochemistry of each product, and also show the mechanism, with the curved-arrow notation for your explanation.

word image 746

(a) Addition of Cl2 (Section 8.8)

(b) Addition of HCl (in the absence of peroxides or other free-radical reagents)

(Section 8-3)

3.) (20 pts) We can synthesize an alkene from an alkyl halide via an elimination mechanism, either E1 or E2, depending upon the conditions used. Consider the following reactions, which use a strong base, KOH, and the products which are the result in the amounts given. (Sections 7-9 to 7-17)

word image 1

(a) Which type of elimination (E1 or E2) is favored by using a strong base? ___________

(b) Explain briefly what Zaitsev’s rule is, and whether it applies only to one of the elimination types or to both.

(c) Explain why the product distribution (%) is what it is, for each reaction. Include a reference to the mechanism (based on your answer in (a)) and the effect of either an intermediate or a transition state, whichever applies.

(1) 2-bromobutane

(2) 2-bromo-2,3-dimethylbutane

(d) Substitution and elimination reactions are often in competition. Briefly explain any effects you might need to consider for a competition with the corresponding substitution in these reactions, such as stereochemistry

Part IV Technical Response (20 pts)

Read the article, “Smelly Science”” [C&EN, July 6, 2020] [Posted on Moodle]

Answer the following questions using the information provided in this article.

You must have legible, complete sentences in order to get full credit for a response.

1. Explain how Witucki isolated and analyzed the substances needed in the dog competition. Include the names of three specific substances as examples. ( 2 -3 sentences)

2. Find a reference about “Myrrh” and give a brief description of its composition, chemically and physically, as well as any interesting properties you find.

( 2 – 3 sentences)

3. What medical application is Witucki particularly interested in studying with dogs’ “nose-work”? ( 1 sentence)

4. Describe the three different conditions for the laundry samples studied in Europe.

(2 – 3 sentences)

5. Identify the particular chemistry applied to sunlight, and give the specific type of compound that results in that “fresh air” smell. ( 1 -2 sentences)

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