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Chemistry 2423
Exam 2A

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O Cimene – refers toseveral isomeric compounds. The Ocimenes are monoterpenes found within varity of plants fruits.

Instructor : Dr. Pahlavan

ORGANIC CHEM 2423 EXAM # 2A Sample(Chapters 5,6, and7) Name:__________________ Score

DIRECTIONS- Please answer all questions in the space provided as completely and clearly as possible . Show all your work for the writing portions of the exam.

PART I – Multiple Choice (3 points each)

_____ 1. Species with unpaired electrons are called ___________________ .

A. molecular ions B. free atoms C. radicals D. electrophiles

_____ 2. Identify the type of the following reaction: [pic]

A. elimination B. substitution C. addition D. rearrangement

_____ 3. Consider the following reaction. Which species is the nucleophile?

[pic] ( I ) ( II) ( III )

A. I only B. II only C. III only D. none of these

_____ 4. This process occurs when both bonding electrons remain with one product fragment.

A. homolytic bond breaking B. heterolytic bond breaking C. hemolytic bond formation D. radical formation

_____5. How many degree of unsaturation are in Valium (diazepam) , C16H13N2OCl ? A. 10 B. 11 C. 7 D. 12

_____ 6. Provide the proper IUPAC name for the alkene shown below.

CH3 – CH = CH – CH2 – CH3

A. n- pentane B. 3-pentene C. 2- pentene D. 2- pentyne

_____ 7. What is the acceptable structure for 1,2-dimethylcyclohexene? [pic]
_____ 8. What two atomic orbitals or hybrid atomic orbitals overlap to form the C = C bond in ethene?

A. sp-sp B. sp2 – sp2 C. sp-sp2 D. sp3-sp3

_____ 9. Which of the following has the highest priority?

A. –CN B. –OH C. - CH3 D. – OCH3

_____10. Which of the following alkenes is most stable? [pic]
_____11. Provide the reagents necessary to complete the following transformation.

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A. KOH /ethanol B. KMnO4 /H3O+ C. CH2I2 /Zn(Cu) D. none of these

_____12. bromination of an alkene occurs with:

A. anti stereochemistry B. cis stereochemistry C. syn stereochemistry D. non Markovnikov addition •
_____13. In a radical reaction, the following step Cl• + CH3 - CH2 - CH3 ( CH3 –CH - CH3 + HCl is an example of______.

A. initiation B. propagation C. termination D. addition

_____14. Addition of HBr to 2-butene is called ___________________.

A. Hydroboration hydration B. Hydrogenation C. Hydrohalogenation D. Hydration

_____15. What is the major of the following reaction?

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PART II – Show your work

16. Naming and structures ( 4 points each)

a) Give the IUPAC name of the following compounds: [pic] I II III

I. _______________________________________

II. _______________________________________

III. ______________________________________

b) Draw structures corresponding to the following systematic names;

(2Z)- 3-methyl-2-pentene 2,3-dimethyl-1-cyclopentene

17. ( 5 points) Show by a series of reactions how could you prepare the following compounds from the indicated starting compound. Be sure to clearly indicate the reagents used in each step. [pic]

18. ( 5 points) Propose a mechanism to account for the shown product. Please show the structures of the intermediates and using curved arrows to indicate electron flow in each step. (Rearrangement may occur)

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19. (5 points) Give the average bond dissociation enthalpies below, calculate the enthalpy change for the following reaction.

CH3 – CH2 – CH = CH2 + H2O ( CH3 – CH2 – CH - CH3

OH

C = C ( 614 kJ/mol), C – O ( 358 kJ/mol), C – H ( 414 kJ/mol), O –H (463 kJ/mol), C – C (348 kJ/mol)

20. Predict the major product of the following reactions. (2 points each)

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Bonus Question ( 10 points) – Please show all your work for complete credit.

Write the radical mechanism for the monochlorination of 2-methylbutane to form 2-chloro- 2-methylbutane. [pic]

ORGANIC CHEM 2423 EXAM # 2A Sample Exam - Answers

PART I – Multiple Choice (3 points each)

1. C 2. C 3. B 4. B 5. B 6. C 7. B
8. B 9. D 10. A 11. B 12. A 13. B 14. C
15. B

PART II – Show your work

16. Naming and structures ( 4 points each)

a) I. 3- Methyl-1-cyclohexene II . (3Z) –2,3,4-trimethyl-3-hexene III. 3,7-dimethyl-1,3,6-octatiene

b) (2Z)- 3-methyl-2-pentene 2,3-dimethyl-1-cyclopentene [pic]

17. ( 5 points) Show by a series of reactions how could you prepare the following compounds from the indicated starting compound. Be sure to clearly indicate the reagents used in each step. [pic]

18. ( 5 points) Propose a mechanism to account for the following reaction. Please show the structures of the intermediates and using curved arrows to indicate electron flow in each step. (Rearrangement may occur)

[pic]

19. (5 points)Using average bond dissociation enthalpies table, calculate enthalpy change for the following reaction. (C-H)

CH3 – CH2 – CH = CH2 + H – OH ( CH3 – CH2 – CH - CH3

( C=C) (H-O) (C-O) OH (C-C)

C = C ( 614 kJ/mol), C – O ( 358 kJ/mol), C – H ( 414 kJ/mol) O –H (463 kJ/mol), C – C (348 kJ/mol)

( H = [ D(C=C) + D(H-O)] – [D(C-O) + D(C-O) + D(C-H)] = [ 614 + 463 ] – [ 348 + 358 + 414] = 1077 – 1120 = -43 kJ

20. Predict the major product in each of the following reactions. (2 points each)

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Bonus Question ( 10 points) – Please show all your work for complete credit.

Write a radical mechanism for monochlorination of 2-methylbutane to form 2-chloro- 2 - methylbutane.

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Chemistry 2423
Exam 2B

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Instructor : Dr. Pahlavan

ORGANIC CHEM 2423 EXAM # 2B Sample Name:__________________ Score

DIRECTIONS- Please answer all questions in the space provided as completely and clearly as possible . Show all your work for the writing portions of the exam.

PART I – Multiple choice : (2 points each)

_____1. For which of the following compounds does radical chlorination give a single monochloro product?: [pic] (I) (II) (III) (IV)

A) (I) B) (II) C) (III) D) (IV)

_____ 2. How do you classify the following reaction? : [pic] A) rearrangement B) elimination C) substitution D) addition

_____3. Which statement is not correct?

A) Radical reaction is a process involving symmetrical bond breaking and bond making. B) Endergonic reaction is a reaction where ΔG° is negative. C) Substitution is a reaction where two reactants exchange parts to give two new products. D) Activation energy is the energy needed by reactants to reach the transition state.

_____4. Consider the following reaction. Which species is the nucleophile? [pic] (I) (II) (III) (IV)

A) (I) B) (II) C) (III) D) (IV)

_____5. Calculate the degree of unsaturation in the formula of diazepam (Valium):C16H13N2OCl A) 9 B) 10 C) 11 D) 12

_____6. Use the following bond dissociation Energies in the table below to calculate ΔH° for

| Bond |D (kJ/mol) |
|CH3CH2O−CH3 |339 |
|CH3CH2O−H |436 |
|H−Cl |432 |
|H−Ι |298 |
|CH3−Cl |351 |
|CH3−Ι |234 |

the reaction of ethyl methyl ether with hydrogen chloride and hydrogen iodide.

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A) ΔH°a’ 16 kJ/mol; ΔH°b’ 33 kJ/mol B) ΔH°a’ − 16 kJ/mol; ΔH°b’ − 33 kJ/mol C) ΔH°a’ 787 kJ/mol; ΔH°b’ 670 kJ/mol D) none of these

_____7. From the above data of ΔH°a and ΔH°b (refer to question 6): which acid would you predict to be most effective for the formation of ethanol? A) HCl B) HI C) both acids D) cannot predict

_____8. The reaction depicted in the energy diagram below can best be described as: [pic]

A) slow exergonic reaction B) fast exergonic reaction C) slow endergonic reaction D) fast endergonic reaction

_____9. Dieldrin, C12H8Cl6O, is a pentacyclic compound formerly used as an insecticide.How many double bonds does dieldrin have?

A) one B) two C) three D) four

____10. Ocimene is a triene found in the essential oils of many plants. What is its IUPAC name, including stereochemistry? [pic]

A) (3Z)-3,7-dimethyl-1,3,6-octatriene B) (3E)-3,7-dimethyl-1,3,6-octatriene C) (5Z)-2,6-dimethyl-2,5,7-octatriene D) (5E)-2,6-dimethyl-2,5,7-octatriene

____11. A neutral molecule containing a divalent carbon with six valence electrons is called:

A) carbocation B) carbanion C) carbene D) radical

____12. Arrange the following bicyclic alkenes in order of increasing stability (least stable to most stable).

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A) III < II < I B) I < II < III C) I < III < II D) II < III < I
____13. Which of the following alkene has the E configuration?:

[pic] [pic] (I) (II) (III)

A) (I) B) (II) C) (III) D) (I) and (III)

____ 14. Arrange the following carbocations in order of increasing stability (least stable to most stable). [pic] I II III

A) III < II < I B) I < II < III C) I < III < II D) II < III < I

____15. In a radical reaction, the step below is an example of: [pic]

A) initiation B) propagation C) termination D) substitution

____16. Predict the major product from the following reaction:

[pic] [pic] [pic] [pic] [pic] A) B) C) D)

____17. Suggest structure (s) for alkene (s) that give the indicated reaction product. [pic]

[pic] (I) (II) (III) A) (I) B) (II) C) (III) D) All of these
____18. Predict the major product of the following reaction: [pic]

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____19. What alkene would you start with to prepare the 2,4-diiodopentane below: [pic]

A): [pic] B): [pic] C): [pic] D): [pic]

____20. Hydroboration/oxidation of alkenes occurs with:

A) anti stereochemistry & Markovnikov regiochemistry B) anti stereochemistry & non-Markovnikov regiochemistry C) syn stereochemistry & Markovnikov regiochemistry D) syn stereochemistry & non-Markovnikov regiochemistry

PART II- Show your work (8 points each)

21. Consider the reaction of 2-bromo-2-methylpropane with water:

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i) Is the reaction of 2-bromo-2-methylpropane with water an example of:

a. a substitution reaction? b. a rearrangement reaction? c. an elimination reaction?. d. or an addition reaction?.

Explain your choice:

ii) The First Step of the Reaction:

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Add curved arrows to indicate electron flow in the First Step.

iii) The Second and Third Steps of the Reaction:

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Label the nucleophile, Nu, and the electrophile, E+, in the blanks provided under the reactant structures (Second and Third Steps).

iv) Draw arrows on the structures above showing electron flow in Second and Third Steps of this reaction.

22. Refer to the reaction of 2-bromo-2-methylpropane with water in question 21.

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a. Using the bond dissociations values in the table below, calculate the ΔH° for this reaction. Show your calculations for full credit.

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b. Draw a qualitative reaction energy diagram for the reaction of 2-bromo-2-methylpropane with water. The first step is the slowest step of the reaction. Fully label the diagram, including the coordinates.

23. Propose a mechanism, showing the structures of the intermediates in the following reaction: [pic]

24. Predict the major product of each reaction. Indicate regiochemistry and stereochemistry when relevant.

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25. What reagent would you use to carry out each of the following transformations? In each reaction place the reagent above the arrow.

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BONUS QUESTION(10 points)- Show all your work.

In an abandoned laboratory has been found a flammable liquid, A, in a bottle bearing only the label "Compound A: C7H12." Government agents have offered you a considerable sum to determine the structure of this compound. After verifying the molecular formula by elemental analysis, you find that Compound A reacts with 1 mol equiv of hydrogen and, after treatment with acidic KMnO4, gives the dicarboxylic acid C (see below). Another bottle from the same laboratory is labeled "Compound B (isomer of A)." Compound B also reacts with 1 mol equiv of hydrogen, but yields cyclohexanone after treatment with acidic KMnO4.
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i) How many degrees of unsaturation does Compound A possess?

ii) From the list below suggest structure for A and B

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ii) What was the other product formed in the KMnO4 oxidation of B?

ORGANIC CHEM 2423 EXAM # 2B Sample Exam - Answers

PART I : 1. C 2. A 3. B 4. B 5. C 6. B 7. B 8. B 9. A 10. B 11. C 12. D
13. A 14. D 15. B 16. C 17. D 18. B
19. B 20. D

PART II :

21. i) [pic]

a substitution reaction: substitution of Br with OH.

ii) The First Step of the Reaction: [pic]

iii) The Second and Third Steps of the Reaction:

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iv)

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22. a. [pic]

ΔH° = D (bonds broken) - D (bonds formed) = (263 kJ/mol + 498 kJ/mol) - (380 kJ/mol + 366 kJ/mol) = + 15 kJ/mol.

b. three steps = three transition states

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23.

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24. [pic]

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25. [pic]

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BONUS QUESTION:

i) D.U. = 1 + C –1/2(H + X – N) = 1 + 7 – 1/2(12) = 2 Compound A possesses 2 degrees of unsaturation:

ii) Compound A reacts only with 1 mole equivalent of H2 : suggest that Compound A has only one C=C (double bound) Oxidation of Compound A with KMnO4 produces only one product: suggest that Compound A is a cyclic alkene. Finally looking at the oxidation product C, and the cyclohexanone, the structures of compounds A & B are:

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iii) The other product formed in the KMnO4 oxidation of B is: CO2