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CH 235 Practice Exam - I

Name.---'-.-A.e-I(.=-~::.c:;t__ J,-=-~=-,,-{-_(Last) (First)

800# _

This exam is divided up into two parts, multiple choice and short answer questions. All workmust be shown in order to receive full credit. Please tum off all electronIc commurucanon

devices.

uestions. Choose the correct answer and record it on the scanrron rovided

1. Which of the following molecules has a molecular dipole?

H H F F H F F F

\ / \ / \=1 \ /C=C C=C

C=C

/ \ / \ / \ / \H H H H F H F F

(a) @D (c) (d)

2. Which of the following compounds is (are) chiral?

CH3

H0)HCH3

H'C~CH'H OH H OH

~I"HH]C

H H CH2CH3

@nlyrI II III

(b) r and II (c) ITand III (d) I, II and 1II

3. What is the IUPAC name of the following compound?

(a) 5,5-dimethyl-3-ethylheptane(c) 3,3-dimethyl-5-ethylheptane

~-ethyl-3.3-dimethYI-heplane(d) 3-ethyl-5,5-dimethyl-heptane

4. Which of the following structures represents trans-i ,2-dimethylcyclohcxane?

d(a) ~

(e)

5. What is the relationship between the following pair of structures?

(a) They are enantiomers(c) The are constitutional isomers

(1;l They are diastereomers@})rhey are identical

6. ~ich of the following cycloalkanes has the highest ring strain?~a) cyclopropane (b) cyclobutane (e) eyclopentane (d) cyclohexane

7. The formal charges of the nitrogen and oxygen in the following structure are, respectively:.,H3C-C==N-5? :

~ +1,-1 (b) 0, -I (e) +1,0 (d) 0, 0

8. Which of the following is a definition of the activation energy of a reaction?

2

a) the difference in Gibbs free energy between the reactants and the transition state(b) the difference in Gibbs free energy between the reactants and the intermediate(c) the difference in Gibbs free energy between the reactants and the product(d) the difference in Gibbs free energy between the transition state and the product

9. Which atomic orbitals overlap to form the C-R 9" bond of ethyne, HC=CH?(a) C2p + HIs (b) CSp3+ HIs (e) Csp"+ HIs ~sp + HIs

10. Among the following four structures, one is not a permissible resonance form. Identify thewrong structure. 10c: ~.,tedt t.+ + \>~. ~ + ..

H2C-Y-~: H2C=y-R: H2C=Y=O: H2C-Y=O:

CH3 CH3 CH3 CH3

(a) (b) CS9 (d)II. Identify the relationship between the following two Newman projections.

H&Cl and H&"HAfAH HAVH

H CI(a) identical (b) different compounds with different constitutions(c) constitutional isomers different conformations of the same compound

12.Give the configurations, respectively, of the following tWOmolecule.

and

H 0~. II

HOCH2 liiio....:<::- -H

/HO

(a) Rand R (b and S (c) Sand S (d) Sand R

13. Identi fy the relationship of the pair of compounds shown below:

HO

@identical compounds(c) constitutional isomers

(b) resonance structure(d) different compound , ith dilTerent compo ition

14.Arrange the following i omeric alkane in order of increa ing boiling point.A. n-heptaneB. 2,3-dimethylpentaneC. 2,2,3-trimethylbutane

(a) A<B<C (b) B< < (e) C<A<B (d C<B<A

15.Which of the following compound will give a pair of diastereorneric alt when reacted with( )-( -)-malic acid

B

(a) only B (b) and B (c) and C (d) A, Band C

3

3. Please answer the following e tions carefully (12 points)

(a) Assign R, S configuration to the chirality centers in the following molecule (Clearly howthe priority as ignments of the groups attached to the chirality ccnters).

II

BrIGH""") ~.

H3C., ~ eOOH

2. CH3"~ t>:-

Br~ H ® #'\

'1

(b) Draw the Fisher Projections for the following molecules.

5

Short answer question ..

I. In stnlctures and S, fill in any lone pairs of elecrrons that are missing and calculate themolecular formula. In tructur C, predict the hybridization of the indicated atoms (10points).

:0

OH .-

..) (B)

(C)

2. iprox ( iprotloxacin) i n ymhetic broad spectrum antibiotic. The structure of Cipro ishown below. Identify the circled functional groups, hybridization of the atoms indicated bylinear arrows and predi t the bond angle indicated by curved arrow (12 points).

\Ad'-t

4

4. Draw the resonance structures for the following species clearly showing the delocalization ofelectrons using curved arrows (12 points). ... -J.

~N

I~l(-o:

rJl "{l'i

',0'·0

)-Iz.,L

:0:

(a)

3. ::.(t! including the shown) ~

(b)

)

6

5. Considering the rotation about C2-C3 bond draw Newman Projections of all eclipsed (three)and all staggered (three) conformations of2 3_dil11ethylbutane and indicate the highest and

. .'lowest energy conformations (12 points).

\

(

( (0\ :s

0 __ p

C\.

L-~"C\-\)60"

Ho: cHs Of)<,

7

·.

6. Calculate the formal charges on the indicated atol11S of the following molecules. Clearlyshow your calculation for each atom in order to receive the full credit (12 points).

5-0_L/~(ij)1-1_ -S-Z- ~ (j)

N,-. S-- 't -0 ~ (j)flJ;l." -r - 2 - 't : tJ)

8