CHEMISTRY 263 - Section A4

MIDTERM – October 22, 2009 - Dr. John C. Vederas

150 Points - 80 Minutes

Part Points

PRINT LAST NAME:

I 56

KEY II 16

ID NUMBER (If Known):

III 24

IV 30

SIGNATURE:

V 24

Total 150

Before you begin be sure that your exam has 13 consecutively numbered pages including this cover sheet. Do not begin until told to do so. When you begin, please print your name on each page of this exam in the upper right hand corner. Loose pages without names will be discarded. Illegible answers will be marked as incorrect. No books, notes, or unauthorized communications are permitted. If you have any questions or problems, please raise your hand. Do not leave your seat without permission. Models are permitted but may not be handed to another and NO CALCULATORS or other electronic devices are to be used. No Notes or books. GOOD LUCK "Nothing is so firmly believed as that which is least known - a persuasion of certainty is a manifest testimony of foolishness." Michael Eyquem, Sieur de Montaigne 1533 -1592 "The reason why we have two ears and only one mouth is that we may hear more and talk less." Zeno of Citium (Cyprus) ca 350 - 260 BC It must not be assumed that atoms of every sort can be linked in every variety of combination. -from On the Nature of the Universe by Titus Lucretius Carus (100-55 BC)

2

NAME__ KEY __________

_____________________________________________________________________________ I. Structure and Nomenclature - 54 Points A. Draw structures for which names are given, or name the given structures by any correct (systematic or common) nomenclature. Be sure to give cis or trans (Z or E), or if appropriate R or S, assignment to the isomer where indicated by asterisks (***). (4 points each) 1. dibenzyl ether

O

2. glycerol

HO OH

OH 3. ethylene glycol

HO

OH 4. 4-hydroxy-3-methoxybenzaldehyde (Available in Safeway as a food additive)

CHO

OCH3

HO

*** 5.

OH

(a C16 compound) (a pheromone which induces interspecies mating of male cotton bollworms with female tobacco budworms thereby killing both) cis-11-hexadecen-1-ol (or Z-11-hexadecen-1-ol) *** 6. (perfume constituent from apples)

trans,trans (or E,E)-3,7,11 trimethyl-1,3,6,10-dodecatetraene

3

NAME_____ KEY ________

_____________________________________________________________________________ 7. para-hydroxyaniline (a photographic developer)

NH2

HO 8. (R)-trans-2-phenyl-3-octene (use part structure below in your drawing to assist grading)

H

B. Determine whether the following pairs of structures are identical, structural isomers, diastereomers or

enantiomers. (4 points each) 1.

OH

and

HO

___Enantiomers__

2.

and

____Enantiomers___

3.

HO

OH

NH2HO

HO

NH2

and

____Identical____

4.

COOH

H OH

H OH

COOH

and HOOCCOOH

OH

OHH

H

_____Diastereomers____

4

NAME_____ KEY _____

_____________________________________________________________________________ C. Zoroastrians utilized the common hemp plant, Cannabis sativa (marijuana), as a mind-altering drug more than 2500 years ago. However the most common use of the plant was to make rope, and it was first imported to Canada in 1606. The major active compound in cannabis is Δ1-tetrahydrocannabinol (Δ1-THC) whose structure is shown below. Examine its structure and answer the questions which follow. Be sure to write your answer clearly inside the boxes where provided. (8 points total - 1 points each)

O

OHH H

chiral center

1 point each

1. The number of carbons in Δ1-tetrahydrocannabinol (Δ1-THC) is: 21

2. The number of hydrogens in Δ1-tetrahydrocannabinol is: 30

3. The number of stereogenic centers in Δ1-tetrahydrocannabinol is: 2

4. The stereochemistry of the indicated chiral center in Δ1-THC is: R

5. The total number of possible stereoisomers of Δ1-tetrahydrocannabinol is 4

(include Δ1-tetrahydrocannabinol in the number) 6. Draw an arrow (---->) to the most acidic hydrogen in the above structure of Δ1-THC

7. The approximate pKa of this most acidic hydrogen in Δ1-THC is about: 10

(round off to integral value)

8. The experimental pKa of water is about (round off to integral value) 16

5

NAME________ KEY ___

_____________________________________________________________________________

II. Physical Properties and Reactivity - 16 points

A. In the group below circle all compounds that have a pKa below (less than) that of water. 2 pts

CH3CH2OHOH

CH3CH2OCH2CH3OH

CH3COOH

O

B. One of the two species below is aromatic and the other is not. Circle the aromatic one. Then give the number

of π electrons that both of them have and list the key criteria that make a molecule or ion aromatic. (4 pts this

question: 1 pt for correct circle, 1 pts correct number electron, 2 pts for requirements for aromaticity below )

O

__8__ π electrons ___6___ π electrons

Key Requirements for Aromaticity are: (2 pts)

cyclic planar fully conjugated 4n+2 π electrons

6

NAME___ KEY ____

_____________________________________________________________________________

C. In the group below use an arrow to indicate position(s) on the aromatic ring which would be most likely to

be attacked by bromine in the presence of AlBr3 (4 pts - 1 pt each)

Example:

CH3

Br OCH3

SO3H

SCH3

H3C

OOK, but hindered

D. Circle the most acidic of the two alcohols shown below. Draw the extra resonance structure of the

corresponding anion to show what makes your choice especially acidic. (6 pts: 1 pt for correct circle)

HO

NO2

HO NO2

O

NO

O

O

NO2

7

NAME____ KEY _____________________________________________________________________________

III. Definitions and Applications - 24 Points

A. Define each of the following terms in 10 words or less (no example necessary) – 2 points each – 16 pts

1. tautomers rapidly interconverting structural isomers

2. LUMO lowest unoccupied molecular orbitals

3. diasteromer a stereoisomer of a compound that is not an enantiomer

4. concerted reaction process in which all bonds form and break at same time

5. inductive effect donation or withdrawal of negative charge through single bonds

6. Lewis acid a substance that accepts a pair of electrons

7. steric effect a repulsive non-bonded interaction between atoms with inert gas configuration

8. resonance forms depictions of same molecule made by moving electrons without change of atom

positions

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NAME_______ KEY _ _____________________________________________________________________________

B. The compounds shown below were discussed in class. Identify them by common name and briefly (10 words or less) describe their importance or use. (8 points total - 2 pts each) 1.

H3C

CH2 CH2n Rubber (1)

Tires (or similar application) (1)

2.

N

NHO

H3CO

Quinine (1) Antimalarial (1)

3

β-carotene (1) occurs in all plants (eg orange of carrots) 4.

Cl

Cl

Cl

Cl

Cl DDT (1) Insecticide or Environmental Contaminant (1)

9

NAME____ KEY ___ _____________________________________________________________________________

IV. Reactions - 30 Points

A. Show the structure of the major organic product of each of the following reactions. Show stereochemistry

where indicated by asterisks (***). (3 points each - 15 points total)

1.

KMnO4

(hot H2O)CO2HHO2C

2.

F

AlCl3

Cl

O

F

O

and/or

ortho isomer

*** 3.

Heat 4.

AlCl3

Cl

5.

N2 Cl

CH3OH

heatOCH3

10

NAME______ KEY ________ _____________________________________________________________________________

B. Show reagents that will do the required transformations. In some cases two steps may be necessary.

(3 pts each - 15 pts total)

1.

O

Zn / HCl

(Hg optional)

2.

OCH2CH3

CH3CH2OH

HCl or other acid

3.

NO2

Cl1. HNO3 , H2SO4

2. Cl2 , AlCl3or other Lewis acid

4.

Cl

O

1. Cl2, FeCl3

2. CH3COCl AlCl3 or other Lewis acid

5.

OHH2OH2SO4

or other acid

11

NAME_____ KEY ______ _____________________________________________________________________________

V. Synthesis and Mechanism - 24 Points

A. The common fabric dye Navy Blue can be synthesized from benzene, naphthalene and the naphthalene derivative shown in several steps. Provide the missing reagents and intermediates to show how to complete the synthesis of Navy Blue. (11 points).

SO3H

HN

HO3S

N N N N

Navy Blue From

SO3H

HN

H2SO4

SO3

HO3S

H2SO4

HNO3

HO3S

NO2

Sn

HCl

HO3S

NH2

NaNO2

HCl

HO3S

N N

Cl

H2SO4

HNO3

NO2

Sn

HCl

NH2

HO3S

N N NH2

NaNO2

HCl

HO3S

N N N N

Cl

Combine Final Product

12

NAME______ KEY _______ _____________________________________________________________________________

B. Versalide has a strong musk odor and is commercially synthesized for use in perfumes. Outline a short synthesis of versalide from benzene, 2,5-dichloro-2,5-dimethylhexane, and any other necessary organic or inorganic reagents. Several steps will be required. (6 points )

O

from

Cl

Cl

and

AlCl3

O

Cl

OCl

Cl

AlCl3

O

AlCl3

Cl

13

NAME______ KEY ________ _____________________________________________________________________________

C. The first steps of a mechanism for the acid-catalyzed polymerization of butadiene are shown below, but

it is missing curved arrows to indicate the movement of electrons as well as charges. Complete the mechanism

by putting in the correct arrows and charges. Check carefully – each one is worth points. (7 Points Total)

H2CCH

HC

CH2

H2SO4

Overall Reaction:

Mechanism: ( add missing charges and curved arrows )

H

HSO4

H2C

CC

CH2

N

CC

CC

CC

CC

H

H

H

H

H

H

H

CC

CC

H

H

H

H

H

H

H

CC

CC

H

H

H

H

H

H

H

CC

CC

H

H

H

H

H

H

H

CC

CC

H

H

H

H

H

H

H

H

CC

CCH2

H

H

H

HH2C

CC

CH

H

H

HSO4

HSO4

HSO4HSO4

H

H H

H

H

H

HH