CHEM 222, Dr. Pat Forgione Mid-Term Exam, October 30th, 2015 STUDENT ID# : __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ Last Name: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ First Name: __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ Answer all questions! Molecular Model kits and calculators are allowed. Fill in your STUDENT ID in the scantron sheet before you begin!

1. Give the major product(s) expected if the following reaction occurred via either an SN2 or an SN1 mechanism (3 points). Explain which mechanism would be more likely given the reagents provided (1 point). Label the stereocentres of both the starting material and all possible products of the reactions as either (R) or (S). (0.5 points each) For how to solve this problem, see Q4 Homework 1. The nuculeophile in this case is a “strong” nucleophile, which favours SN2 reactions. A weak nucleophile (MeOH) would give the SN1 product.

2. What is the major product of the following E2 elimination reaction? (2 points)

For how to solve this problem, see, see Q5 Homework 1.

3. What is the major product of the following reaction? Clearly label (if any) stereocentres and if more than one stereocentre clearly show the relative stereochemistry of the final product (2 points total) For how to solve this problem, see, see Q2 Homework 3.

4. What is the major product of the following reaction? Label the sterocentres in the product and starting material as either R or S (3 points)

BrO-+

+ Na+ -OMe

I

+H O O

O

This is a base opening of an epoxide, which is an SN2-like reaction and therefore there is an inversion of stereochemistry and it happens on the least hindered of the two carbon atoms of the epoxide.

5. What is (are) the major product(s) of the following reaction? Draw a complete mechanism for this transformation, including ALL resonance structures (if any), all charges and every step drawn individually (do not combine steps). (5 points). Provide a starting material and reaction conditions that will produce compound A in one step (2 points).

This is an acid-catalyzed ring-opening of an epoxide, which produces the most stable carbocation as an intermediate. Since this is acid-catalyzed, this usually implies the first step involves the acid

H2OMeLi

O

Me- Li+

O-Me

OHMe

O H+

MeOHO+H

break thebond thatgives themost stablecarbocation

OH

the tertiarycarbocationis now sp2hybridized,therefore thenucleophile (MeOH)can attackfrom either the "top" orthe "bottom"

MeOHOH

O+Me H

+ OH

O+Me H

OH

OMe

OH

OMe

HO O R

O

start from hereto make the abovestarting material inone step.

6. Draw a complete mechanism for the following transformation, including ALL resonance structures, all charges and every step drawn individually (do not combine steps). Clearly label which is the major thermodynamic product and which is the kinetic product? (5 points)

For how to solve this problem, see, see Q2 Homework 2.

7. What is the major product of the following reaction? (3 points)

8. What conditions/reagents would be required for each of the following transformations? (2 pts each)

BrBr+

+150 oC

O

O

O

O

O

O

O

O

O

or

9. Draw the two resonance structures for the following molecule (2 points) with at least one of them containing more than one charged atom. Show all arrow pushing and the use of proper arrow nomenclature.

10. Determine the structure of the following unknown compound based on the given spectra. Explain your reasoning briefly. The integration heights and splitting for the proton NMR are given below. The MS showed the molecular ion peak at 196 with another peak at 198 that was about one-third the intensity (10 points). 1H NMR (m = multiplet, t=triplet, d = doublet)

OH

OH

BrBr

H3O+

Br2

or1. Hg(OAc)2H2O2. NaBH4, NaOH

H2, Pd/C

1. BH3, THF

2. H2O2, NaOH

+ + + +

IR Spectra

13C NMR spectrum

this peak is 2 signals!

Solution:

Cl

O

11. What are the starting materials required to prepare the following in one step via a Diels-Alder reaction? (4 points)

12. Provide either the products of the following reactions or the reagent required for the transformation (8 points total)

CNCN

OH NaBD4

H2CrO4

MeLi

D2O

O

OH

PBr3

H

O

HO

SOCl2

Cl

O

Br

HD

O-

HMe

O-

HMe

OD

LiAlH4 H+

Multiple Choice Questions (1 point each) PLEASE CIRCLE YOUR ANSWER ON THIS BOOKLET AND THE SCANTRON SHEET!

1. Which of the following is the most reactive diene in the Diels-Alder reaction?

Most to least reactive: a > d > b > c > e 2. What is the starting material for the following reaction?

Base opening of an epoxide is an SN2-like reaction with inversion of configuration. Answer is d. 3. What is the major product for the following reaction?

Conversion of alcohols to chlorides with inversion of configuration. Answer is b 4. What is the degree of unsaturation (also called index of hydrogen deficiency) for a compound with the chemical formula of C6H9O2F?

a. 1 b. 2 c. 3 d. 4 e. 5 Answer is b. 5. What is the degree of unsaturation (also called index of hydrogen deficiency) for the following compound?

Two rings plus four double bonds, correct answer is e

a b c d e

O

1. LiAlD4 OH

DH

2. H2O

O

D

O

D

Oa b c d e None

of these

OHSOCl2

a b c d eOSOCl Cl Cl OSOCl

FOH

Br

a. 2 b. 3 c. 4 d. 5 e. 6

6. What is the ratio of peaks expected for dibromomethane in mass spectrometry?

a. Peaks will be observed at m/z of 172 and 174, the ratio will be 1:1 b. Peaks will be observed at m/z of 172, 174 and 176, the ratio will be 1:1:1 c. Peaks will be observed at m/z of 172, 174, 176 and 178, the ratio will be 1:1:1:1 d. Peaks will be observed at m/z of 172, 174 and 176, the ratio will be 1:2:1 e. Peaks will be observed at m/z of 170 and 172, the ratio will be 1

We went over this in class. Answer is d. 7. What is the most likely structure based on following IR spectra?

There is a carbonyl stretch at about 1720 wavenumbers, so this eliminates e. There is no OH stretch, so this eliminates d. There is a C-O-C stretch at about 1290 wavenumbers. There are both sp3 and sp2 CH stretches. Therefore the only possibility is c. 8. Which of the following structures best fits the proton NMR shown below,?

a b c d eO

OO

O

O

O

OH O

a b c d eOH OH O OH a and d areeach possible

Each of the above molucules will have a singlet for the CH3 group and a singlet for the OH group, so these are not easily distinguishable by 1H NMR. However the substitution pattern on the benzene would be distinguishable. If the substituents were para (answer b), we would expect to see 2 signals in the aromatic region. If the substituents were ortho, we would expect to see 4 signals. Since in the 1H NMR we see 3 signals, it can not be b, but could be either a or d. Correct answer is e. 9. What is the product of the following reaction sequence?

Answer is a. 10. What is the major product for the following sequence of reactions?

Williamson either synthesis, answer is e.

OH

a b c d e

1.

2. KCN

S ClO O

CN CN Cl Cl OH

a b c d e

1. KOH

2.HO

I

I O OO

11. What is the major product for the following reaction?

Answer is c. 12. Which of the following statements is not true about the proton NMR spectra you would expect to obtain of the following compound?

a. You will observe a doublet that integrates for 2H’s. b. You will observe a doublet that integrates for 2H’s. c. You will observe a septet that integrates for 1H. d. You will observe a singlet that integrates for 1H. e. You will observe a doublet that integrates for 6H’s. I screwed up this question big-time as a, b and d are all not true. The signals you will see for the above compound are: Singlet, I = 2 Quartet, I = 1 Doublet, I= 3 Septet, I = 1 Doublet, I = 6. I will add 1 point to everyone’s score.

13. In the 1H NMR spectra of the following compound, which statement is correct?

a. A signal will appear that is a triplet and integrates for 2H’s. b. A signal will appear that is a singlet and integrates for 2H’s. c. A signal will appear that is a doublet and integrates for 1H. d. A signal will appear as a triplet and integrate for 1H. e. A signal will appear that is a doublet and integrates for 3H’s.

The correct answer is c. The signals you will see in the 1H NMR are: Doublet, I = 1 Doublet, I = 1 Doublet, I = 2 Multiplet, I = 1

a b c d e

1. Hg(OAc)2 / H2O

2. NaBD4, -OD

DD HO

DD OH HOOH

D

D

Br

Cl

Doublet, I = 6 14. In the 13C NMR spectra of the following compound, how many unique signals should be observed?

a. 11 b. 10 c. 9 d. 8 e. 7 Correct answer is b.

15. What is the starting material required for the following reaction?

Best answer is a.

a b c d e

??OHHO

H3O+

OO Br

OHO