Chemistry 310M/318MDr. Brent Iverson3rd MidtermNov. 30, 2005

NAME (Print): _____________________________

SIGNATURE: _____________________________

Please Note: This test may be a bit long, but there is a reason. I would like to give you a lot of little questions, so you can find ones you can answer and show me what you know, rather than just a few questions that may be testing the one thing you forgot. I recommend you look the exam over and answer the questions you are sure of first, then go back and try to figure out the rest. Also make sure to look at the point totals on the questions as a guide to help budget your time.

Note: You must have your answers written in blue or black pen if you want a regrade!!!!

Do not take this in red ink, as that is what we will use to grade it!

Please print the first three letters of your last name in the three boxes

Please answer the following before you begin:

Have you been to a recitation section since the last

midterm? ____________

10

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11

1

Page Points

Total

TScore

HW

12

14

Pg 1 _____________(23)Signature_________________________

1. (5 pts) Define Hammond's postulate in a concise fashion.

2. (1-4 pts each) Consider the following statements that refers to SN1, SN2, E1, E2 or a radical chain reaction mechanism. To which mechanism(s), if any, does each statement apply?

A. Involves a carbocation intermediateMechanisms

B. Rearrangements can occur during these reactions

C. When reaction occurs at a chiral center on a pure sample of a single enantiomer, a single enantiomer product with inversion of configuration is created.

E. Involves an antiperiplanar transition state geometry

F. The order of reactivity is 3° alkyl halides > 2° alkyl halidesG. The order of reactivity is methyl halides > 1° alkyl halides > 2° alkylhalides and not 3° alkyl halides

H. For alkane starting materials, the order of reactivity is 3° hydrogens > 2° hydrogens > 1° hydrogensI. The reaction that will occur when KOtBu is used

J. The reaction that will occur when Br2 and light are used

K. The reaction that will occur when HBr and peroxides with light are used

L. The reaction that will occur when NBS and light are used

M. Is promoted by polar protic solvents

D. When reaction occurs at a chiral center on a pure sample of a single enantiomer, a mixture of product enantiomers will be created

Signature_________________________ Pg 2 _____________(12)

3. (3 pts) For the following series of compounds, circle the one with the highest boiling point.

H3CCH2

CH2CH3

H3CCH2

CH2OH

HOCH2

CH2OH

4. (3 pts) For the following series of compounds, circle the one with the greatest solubility in water.

5. (3 pts) For the following series of cations, circle the most stable cation.

H3CCH2

CH2CH3

H3CCH2

CH2OH

HOCH2

CH2OH

6. (3 pts) For the following series of radicals, circle the most stable radical.

Signature_________________________ Pg 3 _____________(18)

7. (13 pts total) For each set of reagents below, draw the key transition state that occurs during the indicated reaction. We do not want the entire mechanism or products, just the first key transition state. Use dotted lines to indicate bonds that are in the process of being broken or made. Write any formal charges that you think are important. On the starting structures, draw all appropriate arrows to indicate the flow of electrons.

A.

Transition State

Transition State

H3CC

CH3

H BrSH +

B.

HC C

IH3CH3C

CH3

HOH3C +

8. (5 pts total) For the set of reagents below, draw the first key intermediate that occurs during the indicated reaction. We do not want the entire mechanism or products, just the first key intermediate. Write any formal charges that you think are important. On the starting structures, draw all appropriate arrows to indicate the flow of electrons.

C.

Intermediate

H3CC

CH3

H3C BrOH +

H

CCH3CH2C

CH3H

HBr

H3C

Signature_________________________ Pg 4 _____________(20)

9. (12 pts total) Before the following two alkyl halides react with the strong base via an E2 mechanism, they must adopt a reactive conformation. In the space provided, draw the alkyl halide shown in this reactive conformation that must be present for an E2 reaction to take place. On the reactive conformation you draw, circle the atoms of the alkyl halide that will be removed in the reaction After you draw the E2 reactive conformation, draw the predominant product of the E2 reaction of the alkyl halide with strong base (KOtBu). You may use any type of drawing you wish for these, namely line angle drawings, Newman projections, or chair conformations as appropriate. Please read these directions again so you know what we want!!!

E2 reactive conformation

KOtBu

E2

E2 Product

E2 reactive conformation

KOtBu

E2

E2 Product

10. (8 pts) In the following two sentences, fill the in the blanks with the appropriate numbers.

A) In an SN__ reaction, the "__" in the name means that in the key slow step of the reaction both the

alkyl halide and the nucleophile are involved, so their concentrations are both proportional to the rate

of the reaction.

B) In an SN__ reaction, the "__" in the name means that in the key slow step of the reaction only the

alkyl halide is involved, so its concentration alone is proportional to the rate of the reaction.

CH3

Br

On your answer to question 9 above, did you remember to circle the atoms on the reactive conformations that will be removed?

Signature_________________________ Pg 5 _____________(35)

10. (23 pts total) Complete the following intiation and propagation steps for the addition of HBr via a free radical chain reaction mechanism. Use appropriate arrows to show movement of electron density, and show all non-bonding electrons as dots and show any formal charges.

Initiation

OR O R

+ BrH

same species

Propagation

CC

C

H

H

H

H

H

H

+

BrH+

same specie

s

same species

same species

Products

+

hν

11. (12 pts total) Complete the following mechanism. Use appropriate arrows to show movement of electron density, and show all non-bonding electrons as dots and show any formal charges. Show all products of each step and use wedges and dashes to keep track of stereochemistry.

OH P

Br

Br Br

Br

H CH3

Products

CCH3C

C

Br

H3CH

CH2CH3

C

Br

H3CH3C

CH3

C

Br

H3CH3C

CH2CH3

Br

Na

Na N3

CH3CH2OH

CH3CH2O Na

CH3

I

CH3CH2O Na

Signature_________________________ Pg 6 _____________(27)

12. (5 or 7 pts each) The following reactions all involve chemistry of alkyl halides. Fill in the box above the arrow with the mechanism that will be followed (SN2, E2, etc.). Then draw only the predominant product or products and please remember that you must draw the correct stereoisomers. When a scrambled mixture is formed, you must write "scrambled" under both structures EVEN THOUGH YOU DREW BOTH STRUCTURES. For SN1/E1 reactions you must draw both types of products.

+

C.

A.

E.

B.

+

D.

+

+

+

Signature_________________________ Pg 7 _____________(22)

Br2

Br2

NBS

HBr

HBrROOR

HBr

13. (3 or 5 pts each) For the following, complete the reactions with the predominant product or products. You must indicate stereochemistry with wedges and dashes. If a racemic mixture is created, you must write "racemic" under the structures.

hν

hν

hν

OH

H2

HgSO4H2SO4H2O2 H2

13. (3 or 5 pts each) For the following, complete the reactions with the predominant carbon containing product or products. You must indicate stereochemistry with wedges and dashes. If a racemic mixture is created, you must write "racemic" under the structures.

1) OsO4

2) NaHSO3 / H2O

1) (sia)2BH2) H2O2 / HO

Pd°

Signature_________________________ Pg 8 _____________(22)

Pd°

1) O3

2) (CH3)2S

H2

OH

PBr3

HBr

Large excess

Signature_________________________ Pg 9 _____________(22)

13. (3 or 5 pts each) For the following, complete the reactions with the predominant carbon containing product or products. You must indicate stereochemistry with wedges and dashes. If a racemic mixture is created, you must write "racemic" under the structures, and if the stereochemistry of a chiral center is scrambled, you must write "scrambled".

Na° / NH3

Lindlarcatalyst

Na°

HO

of HBr

Think about this next one!

OH

Signature_________________________ Pg 10 _____________(19)

Cl

ClCl

Cl

14. These are synthesis questions. You need to show how the starting material can be converted into the product(s) shown. You may use any reactions we have learned. Show all the reagents you need. Show each molecule synthesized along the way and be sure to pay attention to the regiochemistry and stereochemistry preferences for each reaction.

?

A) (7 pts)

racemic

H H H2C CH2

HO H

H OH

B) (12 pts)

+racemic

?

H

O O

14. These are synthesis questions. You need to show how the starting material can be converted into the product(s) shown. You may use any reactions we have learned. Show all the reagents you need. Show each molecule synthesized along the way and be sure to pay attention to the regiochemistry and stereochemistry preferences for each reaction.

Signature_________________________ Pg 11 _____________(14)

C) (7 pts)

?

D) (7 pts)

?

OHOH

14. These are synthesis questions. You need to show how the starting material can be converted into the product(s) shown. You may use any reactions we have learned. Show all the reagents you need. Show each molecule synthesized along the way and be sure to pay attention to the regiochemistry and stereochemistry preferences for each reaction. This is a tricky one, so be creative. Please try to give us No BS!

Signature_________________________ Pg 12 _____________(15)

E) (15 pts)

?Br

H OH

H OH

HO H

HO H

racemic

H3CC

OH

OH3C NH3 H3CH2C SH

NHN

NH

O

O

O

OH2C

OO

N

S

NHN

NH

O

O

O

OH2C

OO

N

S

Signature_________________________ Pg 14__________(12)

18. (12 pts) I promised you this one! Complete the following three structures by adding appropriate numbers of valence lone pair electrons, H atoms, and formal charges to the atoms in the boxes. You must adjust your answers to indicate the predominant species at each indicated pH value. (You do not have to add anything such as H atoms to atoms not drawn in the boxes.) This problem is testing your understanding of the relationship of protonation state to pH to pKa values for certain functional groups we have discussed. Next, in the space provided, write the overall charge on each structure at the indicated pH. For your reference, here are the relavant pKa vaules:

pKa = 4.76pKa = 10.64 pKa = 8.5

pH = 13

pH = 6.5

Total charge on molecule:______

Total charge on molecule:______