chem 232 • exam two • april 5, 2010 - uic department of...

CHEM 232 • Exam Two • April 5, 2010

Name_____________________(-1 pt) TA Name___________________(-1 pt) UIN_________________(-1 pt)

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Question 1 [Qualitative Ranking, 40 points] A significant amount of time has been devoted to describing the physical and chemical properties of organic compounds including acidity, bond strength, boiling point, solubility, heat of combustion, conformation, constitution and reactivity. Rank the molecules in each set below according to the trends observed for the physical and chemical properties indicated. A. Rank each of the following alkyl halides in order of increasing rate of SN2 substitution (1 = slowest rate; 5 = fastest rate). (5 pts)

Br Br BrBr

F

1 3 4 2 5

B. 1,3-Dienes and dienophiles undergo Diels-Alder cycloaddition to form cyclohexenes. Rank the following diene/dienophile

combinations in order of decreasing rate of reaction (1 = fastest reaction, 4 = slowest reaction). (4 pts)

OMe

OOMe

O

OMe

O

OMe

O

OMe

O

OMe

1 43 2

C. Rank the rate of SN1 substitution in each of the solvents below in increasing order (1 = slowest SN1 reaction, 5 = fastest SN1

reaction). (5 pts)

(ε = 21) (ε = 33) (ε = 78) (ε = 58)

H O HMe O H O HO

H

(ε = 9)

CH2Cl2Me

O

Me

3 12 45



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D. Rank the following molecules in order of increasing number of chiral centers dipole moment (µ) (1 = lowest dipole moment, 4 = highest dipole moment). (5 pts)

OHOH

OH

OHOH

HO

OHH H

OHHOHOF

FF

FF

F

F F

F

FF

F

3 124 5

E. Rank the following anions in order of decreasing leaving group ability (1 = best leaving group; 5 = poorest leaving group). (5

pts)

S OO

OH3C F Me O Cl

S OO

OF3C

32 4 5 1

F. Based on your knowledge of the periodic table (see final page), rank each compound/anion in order of increasing nucleophilicity

(1 = least nucleophilic; 5 = most nucleophilic) (5 pts)

O- Na+

O

S- Na+Se- Na+ S- Na+

O

O- Na+

31 5 2 4

G. Rank the following molecules in order of increasing heat of combustion (1 = least exothermic, lowest ∆Hcomb, 6 = most

exothermic, highest ∆Hcomb). (6 pts)

15 3 4 26

H. Rank the following carbocations in order of decreasing stability (1 = most stable, 5 = least stable). (5 pts)

H

H

H

H

H

H

H

H H

13 2 45



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Question 2 [Predict-the-Products, 50 points, 5 points each] Draw the major organic product(s) for each of the reaction schemes below. Indicate charged atoms. For Brφnsted acid-base reactions, draw both conjugates.

light (hv)Br2

2 x HF

+ OMe

O

NC

MeO

H 1. Pd/CaCO3 lead acetate quinoline

2. BH3•THF, then H2O2/NaOH

Na

NH3(l)

single isomer

H CH3

TsO H

CH3

CH3

MeS- Na+

EtOH

1. t-BuOK

2.

Br

heat

Na2S

(S2- anion)

TsO OTs

C9H18S

HCl

-78 °C

single isomer

Br2

Me O

OO

H

CN

O

OMe

CN

O

OMe

or

MeO OH

Br

FF

H CH3

H SMe

CH3

CH3

HCl

S

O

Br

Br

Br

Bror

O

or

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Question 3 [Mechanisms, 40 points] A. Draw a reasonable arrow-pushing mechanism for the following transformation. (10 pts)

Me

H H

H

Cl

HOH H

H

HO

Me

HCl

B. For the following first order nucleophilic substitution (SN1) reaction, draw a reasonable arrow-pushing mechanism. Account for why this transformation proceeds with 66% net inversion rather than racemization (10 + 5 pts)

BrH OHH HHO

(S)-2-bromooctane (1) (S)-octan-2-ol (2) (R)-octan-2-ol (3)

83% yield17% yield

EtOH, H2O+

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A. Draw a reasonable arrow-pushing mechanism for the following transformation. (15 pts)

Cl

CF3

HN

Cl

CF3

HNOH1. HBr

2. H2O

1 2

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Question 4 [Synthesis, 40 points; 15 + 25 points] Devise a synthesis for both target molecules (products) below. Write the forward synthesis from the reactant(s). Include all necessary conditions above/below the reaction arrow for each transformation. Write out the product for each transformation in your synthesis separately. You may write out a retrosynthetic analysis; however, only the forward synthesis will be graded. More than one synthesis may be possible for each

OH

Cl

Br ?

OH

Cl

Br NaOH, NaOEtor tert-BuOK Cl2

H2O

HO

H ?

HO

H

MsCl or TsClpyridine

RSO2O

or

HO

NaBr

H2SO4 Br

Na+ -NH2 Br

RSO2O

H2, Pd-CaCO3

lead acetatequinoline

or

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Question 5 [Stereochemistry & Structure, 40 points] A. (i) Mark all the chirality centers in the structures of the naturally-occuring cell migration inhibitor Moverastin (1), the anticancer agent puraquinonic acid (2) and the lipid-lowering drug Lipitor (3) with an asterisk (*). (10 pts) (ii) Using the Cahn–Ingold–Prelog (CIP) priority rules, determine the absolute configuration and assign an R or S descriptor to each chirality center within molecules 1, 2, and 3. (14 pts)

Moverastin (1)

O

HO

CHO

OH

HO

O

O

HO

O

OH

(-)-Puraquinonic Acid (2)

O

OH

OHOH

NO

NH

F

Lipitor (3)

*** *

* *R

*R

R

S

R

R R

B. Which of the following molecules are chiral, which are achiral?. (8 pts)

CO2H

OH

OHHO

HOHO O Me

OO HH

Cl

Cl

CO2H

OH

OHHO

HOHO O Me

OCl

Cl Cl

Cl

achiral chiral achiral chiral

C. What isomeric relationship do the following pairs of compounds have with each other? (12 pts)

(a)

(b) and

(c) and

(d) andOH

OHOH

OH

OHOH

O OO

H O

Hand

enantiomers enantiomers

conformersdiastereomers

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Question 6 [Functional Groups, 30 points; 5 points each] Write the name for the principle functional group present in each molecule (e.g. ketone, alcohol, etc.). Do not write the IUPAC name or common name for the molecule, just the functional group name. Names must be spelled correctly for credit.

Cl

O O

H

CH

H

NO2

OH

NH

acid chloride

allene

nitro group amine

enol

aldehyde

chem 232 • exam two • april 5, 2010 - uic department of...

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