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Chemistry 2302 Exam 3 Prof. Douglas April 27, 2016

Last Name: _____________________ (please print) First Name: _____________________ Student ID: _____________________ Put a Check [✔] in the brackets below if it is OK to hand back this exam in a box outside of Prof. Douglas’ Office and/or in class. Note: your score does not appear on this face page. If not checked, your exam can be picked up at Prof. Douglas’ Office hours

[ ] General Instructions & Tips: 1) Use pen, cross out anything you don’t want us to grade. 2) Electronic Devices of any kind are not allowed: turn off and stow. 3) Carefully read all instructions for questions. Do not assume that the instructions are identical to the practice exam or old exams. 4) Model kits, calculators, and stencils are not allowed. 5) Maximize partial credit by first attempting questions you feel you can answer correctly, rather than tackling problems in sequence. 6) Clear drawings make it easy to assign full/partial credit. 7) There is at least one problem on each page except this one: don’t miss any!

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Last Name: _____________________ (1 bonus point) First Name: _____________________ Student ID #__________________ Point Tally: Bonus Point /1 Problem 1. /24 Problem 5. /22 Acids & Bases Carbonyl rxns & mech part 2 Problem 2. /23 Problem 6. /10 Amines Multistep Synthesis Problem 3. /22 Carbonyl rxns & mech part 1 Total: /100 Problem 1, Acid & base strength: Part 1: (12 pts, 2 each) In the space indicated, draw the conjugate base of each molecule in the chart above. In cases where the molecule has more than one acidic carbon, draw the conjugate base resulting from thermodynamic deprotonation. Part 2: (12 pts, 2 each) For each boxed pair, circle the molecule that is the stronger acid.

t-Bu

O O

O

OMe

O

NH2

NH

NNNNH

OH

NH2

O

NH

H2N

Draw conjugate bases below.

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Problem 2, Amines: Multiple Choice & Short Answer, (22 points, values indicated below) Answer the following questions about benzphetamine, a habit-forming diet pill that is listed as a controlled substance in the USA.

N

Me

Me

Didrex

A) How many stereogenic centers are in Didrex? Circle your choice below. (1 points)

a) zero, b) one, c) two, d) three, e) more than three

B) Draw the structures of two different amides that would form Didrex after reduction with LiAlH4, followed by work up with water. (4 points, 2 points each) C) What two alkene products are formed by Hofmann Elimination of Didrex? (treatment with excess MeI, then Ag2O, then heat). (2 points each) Indicate the major product. (2 points) (6 points total) D) What carbonyl compound and amine can be used to make Didrex by reductive amination? Draw two of the possible three carbonyl/amine pairs. (2 points for each structure, 2 points for indicating correct pairs of carbonyl/amine, 12 points total) Bonus point: Circle the minimum portion of the Didrex molecule that is most responsible for its psychoactive properties.

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Problem 3, Carbonyl compounds & mechanisms: Multiple Choice & Short Answer, (22 points, values indicated below) A) (3 points) The di-ketone shown is called the Wieland-Miescher ketone. Draw the starting material that would be needed to form alpha-beta unsaturated ketone portion of this compound by an intramolecular aldol cyclization.

O

OH3C

Wieland-Miescher ketone B) (6 points, 3 points each) Draw the structures of the two carbonyl compounds needed to prepare your compound in part A via a Michael Reaction. C) (10 points) Draw a mechanism for the Micheal Reaction of your compounds in part B. Use NaOH as the base catalyst. (4 points for correct arrows, 4 points for correct intermediates with correct formal charges, 2 points for correct sequence of events) D) (3 points) The two steps above could be run in one base-catalyzed process. That particular combination is a tandem reaction called the _______________. a) Robinson Annulation d) Malonic Ester Synthesis b) Acetoacetate Synthesis e) Curtius Rearrangement c) Gabriel Reaction

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Problem 4, Carbonyl compounds & mechanisms part 2: Multiple Choice & Short Answer, (22 points, values indicated below) A) (9 points, 3 points each) Draw the structures of compounds A–C in the following synthesis of ibuprofen from 2-(4-isobutylphenyl)acetic acid. Be sure to label your structures A, B, & C.

H3C

CH3 [1] SOCl2 A B[1] NaOEt

[2] CH3IC

heat

H3O+

H3C

CH3

CH3OH

O

ibuprofen

CO2H

O

OEtEtO

[2] EtOH pyridine

NaOEt

B) (6 points) What do you expect when acetone (2-propanone, shown on the right)… …reacts with excess NaOH and I2? … reacts with acetic acid and Br2?

a) an aldol polymer will form a) an aldol reaction b) 1-iodo-2-propanone b) 1-bromo-2-propanone c) hexa-iodo-acetone (2 CI3 groups) c) 2-bromoethanoic acid d) iodoform (CHI3) d) bromoform (CHBr3) e) none of the above e) none of the above

C) (4 points) Draw a three step synthesis of the cyclic ketone below that uses the starting materials shown. Your synthesis should include a Dieckmann Reaction and an Acetoacetic Ester Decarboxylation. Show intermediates and reagents (or reaction conditions) for full credit.

MeO

OOMe

O

OBr

D) (3 points) Draw the expected product. You may ignore stereochemistry.

O

CH3

[1] LDA, –78°C

[2] CH3CH2I

H3C CH3

O

propan-2-one

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Problem 5 (10 points, 5 each) Propose multistep synthesis routes to the compounds shown using the starting materials shown and any other reagents/reactants you need. To maximize partial credit, be sure to draw out the products of each reaction you propose. No partial credit will be awarded for reactive intermediates/mechanisms (such as carbocations). Note: Full credit will be provided if your conditions provide selectivity for the desired product if mixtures can result. a. Choose Only One!

O

CH3 t-Bu NH2 ORO

Nt-Bu

H OCH3I

H3C OEt

O O

O

CH3

CH3

b. Choose Only One!

Br

Br BrOR

O

H3C H3C

O

CH3

CH3

CH3

OH