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CHEM 2OA3 Midterm Test October 23, 2008 VERSION 1

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CHEM 2OA3 Midterm Test October 23, 2008 VERSION 1

NAME (First & Last): ___ _____________

ID#: _______________

Lab Station: ______

(1-72, Print ‘E’ if you are exempt from the labs)

Please circle your lab section in the table below.

Group Monday Tuesday Wednesday Thursday Friday

I L01 L02 L03 L04 L05

II L06 L07 L08 L09 L10

Duration: 90 minutes Instructor: Harald Stöver

Instructions:

This examination paper consists of 20 pages, containing 22 (twenty two) multiple choice (MC) questions, and 3 short-answer questions. You are responsible for ensuring your copy of the question paper is complete and no pages are missing. A mini-periodic table and spectral correlation charts are provided on the last two pages. Feel free to detach these last pages for easier use.

Answer all the MC questions on optical scan sheets. Each MC question is worth two marks and you will not be penalized for incorrect answers. Follow the instructions on the optical scan sheets, and the University rules for OMR exams which are reproduced on page 2. Failure to follow instructions may result in loss of credit.

You are responsible for ensuring all answers are in the correct place, and that you follow the correct procedure for filling out the scan sheet.

Mark your student number in the space provided on the sheet on Side 1 AND FILL IN THE CORRESPONDING BUBBLES UNDERNEATH. Now enter your version number, which can be found on the top right hand corner of this page, by filling in the BUBBLE in the “version” column provided. You MUST sign the sheet in the space provided.

All McMaster rules and procedures relating to Academic Dishonesty and Academic Integrity apply to this exam; all violations will result in a penalty. Students must do their own work. A program designed to detect similar answers will be used for this exam.

You MUST also complete ALL the information at the top of this page.

MC

Written Section

Q23

Q24

Q25

Written Total

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OMR EXAMINATION – STUDENT INSTRUCTIONS

NOTE: IT IS YOUR RESPONSIBILITY TO ENSURE THAT THE ANSWER SHEET IS PROPERLY COMPLETED. YOUR EXAMINATION RESULT DEPENDS UPON

PROPER ATTENTION TO THESE INSTRUCTIONS.

The scanner, which reads the sheets, senses the bubble shaded areas by their non-reflection of light. A heavy mark must be made, completely filling the circular bubble, with an HB pencil. Marks made with a pen will NOT be sensed. Erasures must be thorough or the scanner will still sense a mark. Do NOT use correction fluid on the sheets. Do NOT put any

unnecessary marks or writing on the sheet.

1. On SIDE 1 (red side) of the form, in the top box, print your student number, name, course name, and the date in the spaces provided, in pen. Then you MUST write your signature, in the space marked SIGNATURE.

2. In the second box, mark your student number and test or exam version number (1, 2, 3 …) by filling in the corresponding bubbles underneath, in pencil.

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1. When the 1s orbitals of two hydrogen atoms combine to form a hydrogen molecule, which molecular orbitals are formed?

A. One bonding molecular orbital only B. Two bonding molecular orbitals

C. One bonding molecular orbital and one antibonding molecular orbital D. Two antibonding molecular orbitals

E. Three bonding molecular orbitals

2. The following electron configuration represents:

1s 2sp3 2sp3 2sp3 2sp3

A. the ground state of boron.

B. the sp3 hybridized state of carbon. C. the sp3 hybridized state of nitrogen. D. the ground state of carbon.

E. an excited state of carbon.

3. VSEPR theory predicts an identical shape for all of the following, except: A. NH3

B. H3O+

C. BH3

D. CH3-

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4. Increasing s character makes for shorter bonds.Which is the shortest of the carbon-carbon single bonds indicated by arrows in the following compounds?

A. H3C CH3

B. H3C C CH

C. H3C CH

CH2

D. HC C C CH

E.

H2C

HC C CH

5. Which of the following is a set of constitutional isomers?

Br Br

Br

Br

IV III

II I

A. I and II B. II and III C. I, II, and III D. II, III, and IV E. I, III, and IV

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6. Which of the following compounds would you expect to have the lowest boiling point? NH2 O H N O N O NH2

O O NH

A. B. C. D. E.

7. Which of the following ions is NOT stabilized by resonance?

O O O O A B C D E

8. Which compound can be classified as an ester as well as a ketone?

O O O O O O O O O OH O

I II III

IV V

OH O

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9. How many 2° alkylchlorides, counting R, S stereoisomers, are possible with the formula C5H11Cl?

A. 3 B. 4 C. 5 D. 6 E. 7

10. The IRstretching frequency can be predicted to occur at the highest frequency for which of these bonds?

A. C–H B. C–F C. C–Cl D. C–Br E. C–I

11. An organic compound which shows sharp IR absorptions at 2200 cm-1 and 3300 cm-1 is likely to be what type of compound?

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12. Which of the acids below would have the strongest conjugate base? A.CH3CH2OH

B. CH3CO2H

C. ClCH2CO2H

D.Cl2CHCO2H

E. Cl3CCO2H

13. Which acid-base reaction would not take place as written?

A. CH3Li + CH3CH2CH2CH2NH2 → CH4 + CH3CH2CH2CH2NHLi

B. CH3C≡CH + NaOCH3 → HC≡CNa + CH3OH

C. HC≡CNa + H2O → HC≡CH + NaOH

D. CH3OH + NaNH2 → CH3ONa + NH3

E. CH3CO2H + CH3ONa → CH3CO2Na + CH3OH

14. The reaction of the Na salt of 3-methyl-1-pentyne with 1-bromo-3-methylbutane produces which of these?

A. 3,8-dimethyl-4-nonyne B. 2,7-dimethyl-4-nonyne C. 3,8-dimethyl-5-nonyne D. 3,7-dimethyl-4-nonyne E. 3,7-dimethyl-5-nonyne

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15. Which of the following can be described as trans isomers?

CH3

CH2CH3 Cl CH3 Br HO CH3 HO Br F

I

II

III

IV

V

A. I B. II, V C. I, III, IV D. III and IV E. None of the above

16. The graph below shows the relative rotational energies of hexane, viewed through the C2-C3 bond. The conformations corresponding to the 60o and 300o are:

0o 60o 120o 180o 240o 300o 360o

R

e

la

ti

v

e

en

er

g

y

Angle of rotation

A. Eclipsed

B. Staggered and gauche

C. Staggered and anti

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17. How many chirality centers are in Lovastatin ( Mevacor® : a cholesterol-lowering drug) ?

O HO

O

O

(Lovastatin)

A.4 B. 5 C. 6 D.7 E. 8

18.Which compound would show optical activity? A.cis 1,4- Dimethylcyclohexane B. trans 1,4- Dimethylcyclohexane C. cis 1,4- Dimethylcycloheptane

D.trans 1,4- Dimethylcycloheptane E. More than one of these

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19.A solution of which of these allenes will rotate plane-polarized light?

C C C

H

H H

H

C C C

H

Cl H

H

C C C

H

Cl Cl

H

C C C

Cl

Cl Cl

H

C C C

Cl

Cl Cl

Cl

I

II

III

IV

V

A. I B. II C. III D. IV E. V

20. Which of the following molecules is/are a meso compound?

CH3 CH3 Br H Br H

H3C

CH3 H

H

OH

OH H3C

F H

H

CH3 F

I

II

III

A. I B. II C. III

D. More than one of the above E. None of the above

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21.The molecules shown are:

H

CH3 OH H

Br H

H

CH3 OH H

H Br

A. constitutional isomers. B. enantiomers.

C. diastereomers. D.identical. E. None of these

22. Reverse phase chromatography works on the same concepts as regular chromatography except for one key difference: the solid phase (polar silica in regular chromatography) is coated with a layer of NON-POLAR hydrocarbon chains. With this in mind, which of the five compounds shown below would elute first from a REVERSE phase chromatography column.

O

N

OH

A B C

D E

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Three Short Answer Questions [values in square brackets]:

23. [16] Shown below are four pairs of C-13 NMR and Infrared spectra, followed by six chemical structures.

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NH2

NH2

N N

OH O

OH O

O O H

N

O O

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24. [18] Complete the reaction schemes shown below by filling in the missing starting materials, reagents, and products in the boxes provided.

Cl

Br

O H

C H3 Cl

H

: +Na + NH

3

-H2 (excess) / Pt

NaNH2

1.

2. H2 (excess) / Pt

Li

(excess) H2O

HBr (conc) Zn / HBr

H2 / Pt

1 1

Complete the templates of these two products by adding methyl groups and tert.-butyl groups in the correct locations to give the lowest energy chair conformation.

+

1

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5

6

4

5

6

4

H

Cl

(conc.)

+ H

2

O

+

25. [22] Answer the questions below regarding the SN1 reaction (a nucleophilic substitution) of

a substituted cyclohexanol. Read the whole question before answering:

a. [4] Draw S-3,3-dimethyl-1-ethyl-cyclohexan(1-ol) in the most stable chair conformation, by completing the chair template below. The numbers 4, 5 and 6 refer to the ring carbons – make sure you place your substituents on the correct ring carbons, and use correct orientations for axial and equatorial bonds.

b. [2] Redraw the starting material, using the template below. Then draw the two shortlived and reactive ionic intermediates formed in the first and second steps of the reaction into the two boxes below, using the same orientation of the chair as in the starting material.

Ionic Intermediate 1 Ionic Intermediate 2 c. [4] Draw all lone pairs and all curly double-barbed arrows showing electron pair

movement, into the above reaction.

d. [4] Draw the Ionic Intermediate 2 plus any relevant reagent species into the box below, and complete the reaction to form the two immediate products, 1 and 2. Use curly arrows labeled 1 and 2 to show how they form.

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4

5 6

5

6

4

e. [2] Describe, in two or three words, the stereochemical relationship between the two final products:

f. [2] Describe, in one sentence, whether you would expect the products to have higher, the same, or lower enantiomeric excess than the starting material, and why.

g. [2] Describe in one sentence, giving wavenumbers and functional group information, how you could use IR spectroscopy to determine whether the reaction has taken place:

h. [2] One of products 1 and 2 can interconvert into a more stable chair conformation. Redraw that product (as formed in d.) in the left box, using the template provided, and then draw it in the right box in its more stable chair conformation:

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Acid

p

K

a

H

I

H

Br

H

Cl

H

2

SO

4

H

3

O

+

H

3

PO

4

CH

3

CO

2

H

H

2

CO

3

N

H

4+

H

CO

3

-H

2

O

CH

3

CH

2

O

H

C

H

3

C=OMe

HC C

H

H

2

N

H

3

CH

2

=C

H

2

CH

3

C

H

3

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References

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