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Homework 1Organic Chemistry MCAT ReviewSummer 2012Brent Iverson

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1. The most important question in chemistry is: _________________________________________?Where are the electrons

2. Atoms prefer a filled ____________________ shell of electrons. The vast majority of stable

bonding in molecules takes place in such a way that this is accomplished.

valence

3. Neutral carbon takes part in ____ bonds and has ____ nonbonded pairs of electrons.4 0

4. Neutral nitrogen takes part in ____ bonds and has ____ nonbonded pairs of electrons.3 1

5. If a carbon atom in a molecule has three bonds and one nonbonded pair of electrons around it OR if an oxygen atom has one bond and three nonbonded pairs of electrons around it, either

atom will have a ____ formal charge.-1

6. When two atoms of different electronegativity form a covalent bond, the majority of shared electron

density is found around the ____________ electronegative atom.more

7. For the following molecular formulas, draw complete Lewis line structures in which all atoms (even H atoms) are drawn, lines are used as bonds, and all lone pairs and formal charges are drawn.

A)

B)

(CH3)3CCH2CH2CO2H

CCCHH

H

CHH

HCH

HC

H2CCHCH2CHCH2

H

HC

O

O H

CCH

H

H

C CH

H C

H

HH

H

HH

CH3OCH2CH2NH3C)

CH

H

H

O C

H

H

C

H

H

N

H

H

H

3

F. CH2CHCHCH2D. CH3CH2CH3

CC

C

H

H

H

H C

H

H

C

H

H

C

H

H

H

E. (CH3)2CHCH3

C C

C

CH

H

H

H

HH

H

H

H

H

CH

H

H

N

H

H

C

H

H

H

8. Some of the molecules shown below have formal charges. For those that do, write the correct formal charge next to the appropriate atom. IN ADDITION, SOME OF THE ATOMS ON THESE MOLECULES NEED LONE PAIRS ADDED. ADD ALL VALENCE LONE PAIRS OF ELECTRONS WHERE APPROPRIATE.

B

H

HH

CH

H

H

C

H

H

O

CF

F

F

C

H

H

C

O

OH

O

H

HH

G. CH3NO2

C

H

H

H

N

O

O

H

C

H

H

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9. For the following molecules, write the hybridization state of each atom indicated by the arrow.

O

sp3sp3

sp2

sp2

N

sp3

sp

sp2

CC

CH

O

H

HH

sp2

sp2

sp2

CH

H H

sp3

N

N

H

CH3

sp2sp3

sp3

Nicotine

sp2

O O

OO

NHH

HNa

MSG

sp2

sp3

sp2

sp2

HC

CC

H

O

H

HH

sp2

sp2

CC

C

H

H

H

H

H

sp2

sp2

sp2

CH

H

H

NO

O

sp2

sp2

C C

C

CC

C

HH

H

H H

C

H

H

C

H

H

C

H

NH H

C

H

H

H

Amphetamine

sp3

sp3

sp3sp2

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10. Describe each bond indicated with an arrow as the overlap of orbitals. For example, an

answer might be σCsp3-Csp3.

HC

CC

CH

O

H

σ Csp2-Csp2

σCsp2-Csp2

σCsp3-Csp2

π C2p-C2p

HC

CC

H

HH

σ Csp-H1s

π C2p-C2p

π C2p-C2p

σCsp-Csp

σCsp3-Csp

σCsp3-H1s

σCsp3-H1s

H

H

H

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10. (cont.)

σOsp3-H1s

π C2p-O2pσCsp2-Osp2

O

O

H

CH3

H3C

CH3

Ibuprofin

σCsp2-Csp3

σCsp3-Csp2

N

N

N

O

CH3

H

π C2p-C2p

σCsp2-Csp2

σCsp2-Csp2

σCsp2-Nsp2

σ Nsp2-Csp3

LSD

NH3C C

O

σNsp2-Csp

π N2p-C2p

σ Nsp2-Csp3

MethylIsocyanate

(the molecule that cuased the Bhopal tragedy in India in

1984)

σ Csp3-Csp3

σ Csp-Osp2

π C2p-O2p

Note this O atom will have some sp2 character, but is mostly sp3.

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11. The following molecules are best represented as the hybrid of contributing structures. Draw the second important contributing structure in the space provided, including all lone pairs and formal charges. For the structure on the left, use arrows to indicate the movement of electrons to give the structure you drew. Finally, if one of the two contributing structures makes a dominant (major) contribution to the resonance hybrid, draw a circle around the dominant (major) contributor. You might want to read these directions again to make sure you know what we want.

A.

CH

H

H

CO

OCH

H

H

CO

O

B.

C.

C NH

HN C N

H

HN

D.

HC

CC

H

H

HH

HC

CC

H

H

HH

CH

H

H

CC

OCH

H

H

CC

O

HH

HH

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11. (cont.)

HC

CO

HH

OH

C

H

H

HH

CC

O

HH

OH

C

H

H

H

HC

CO

HH

C

H

H

HH

HC

CO

HH

C

H

H

HH

CC

H

H

H N H CC

H

H

H N H

CC

CH

O

H

HH

H

CC

CH

O

H

HH

H

E.

F.

G.

H.

HC

CO

HH

OH

C

H

H

H

either of these are correct

filled valence

filled valence

negative charge on more electronegative element

filled valence

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12. (10 pts each) The following molecules are best represented as the hybrid of three contributing structures. Draw the second and third important contributing structures in the spaces provided, including all lone pairs and formal charges. For the two structures on the left in each problem, use arrows to indicate the movement of electrons to give the structures you drew. There is no need to draw any circles around any of these contributing strucures. You might want to read these directions again to make sure you know what we want.

A.

O CO

O

B.

C NO

O

H

H

O CO

OO C

O

O

C NO

O

H

HC N

O

O

H

H

OORibbit

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13. Draw a circle around all of the molecules below that can be considered aromatic.

N

N

N

H

H

NH

HN O

NN

NN

14. On the left is drawn the Lewis structure of a simple amide. Draw the two next most important contributing structures in the spaces provided. Be sure to show all lone pairs and formal charges. You do not need to draw arrows on the structures, but you can if it helps you.

H

CH

H

CO

N H

H

H

CH

H

CO

N H

H

H

CH

H

CO

N H

H

An important feature of an amide bond is that there is a partial double bond between the carbonyl carbon and nitrogen. For the contributing structures you drew in Problem 2., draw a circle around the one that predicts this partial double bond.

Notice This

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15. On the lines provided, state the hybridization state of the atom indicated by the arrow.

sp2

16. On the lines provided, state the atomic orbital that contains the lone pair of electrons indicated by the arrow.

2p

N

H

H

H

H

H

N

O

CH3

CH3

NH3C

CH3

sp2

sp2

sp3

N

H

N

Hsp2

sp2N

N

sp2

sp2

sp2

N

H

H

H

H

H

N

O

CH3

CH3

NH3C

CH3

sp3

N

H

N

H

N

N

sp2

sp2

2p

2p

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17. Name the circled functional groups present in the following molecules.

OHN

O

O

HO

O

HO

amide

ketoneether

alcohol

carboxylic acid

ON

O

O

O

O

H

nitrile

aldehydeanhydride

N

imine

H3CO

acetal

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17 (cont.) The drug Etoposide is a chemotherapeutic agent that has been used against a number of cancers over the years. It operates by inhibiting an enzyme called topoisomerase that is required for DNA replication. Cancer cells need to replicate faster than normal cells, so drugs like Etoposide can be used to kill cancer selectively. Look at Etoposide and identify the three acetals and one lactone.

OO

O

OH

HO

H

H3C

O H

O

OO

OH

OH

OCH3

H3CO

Acetal

Acetal

Acetal

Lactone(an ester)

Etoposide

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18. On the line provided, write IUPAC names for the following molecules.

CH2H3C C CH2 CH2 CH

CHH3C CH3

CH2 CH2 CH2

3,3-diethyl-6-isopropyldecaneor 3,3-diethyl-6-(1-methylethyl)decane

6-sec-butyl-2,2-dimethyldecaneor 2,2-dimethyl-6-(1-methylpropyl)decane

CH3 C

CH3

CH2

CH2

CH3

CH CH CH

CH3

CH3

CH3

CHCH3 CH3

2,3,4,5,7,7-hexamethylnonane

1 2 3 4 5 6 7 8 9

1

23

45

67

89

9

8

7 6 5 4 3

21

CH2

CH2

CH3

CH3

CH3

10

10

15

19. In the space provided, draw the following molecule:

COOH

I

H3CN

CH3

O

CH3

O

OO

OO

(3R,4S,6R)-4-Iodo-3,6-dimethyloctanoic acid

N,N-Dimethyl-3-oxopentanamide

Cis-Diisopropyl cyclopentane-1,3-dicarboxylate

18. (cont.)

16

OH

O O

NH2

O

H-I Cl H-Cl

OH

OH

I

O

O

NH

20. For the following acid base reactions, circle the side of the equation that predominates at equilibrium.

+ +

+ +

+ +

resonance stabilized anion

oxygen is more electronegative than nitrogen

Iodine is a larger anion than chloride

In each case identify the stronger and weaker acids by comparing relative stabilities of the anions which are the conjugate bases of the two acids. Equilibrium favors formation of the weaker acid. You will notice this means you circled the side with the more stable anion.

SO

OH2C CH3+

H HpKa = 20

OH H +H

N H OH +H

N HH

CFF

FC

OH

O+ CCl

Cl

ClC

O

OCFF

FC

O

O+ CCl

Cl

ClC

OH

O

SO

OH3C CH3+

H pKa = 23

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21. Rank the following from 1 to 4 with respect to relative anion stability, with a 1 under the most stable anion and a 4 under the least stable anion.

OH

HH

OH

HCl

OCl

HCl

OF

FF

4 3 2 1

Inductive effects

23. At pH 7.0 in water, circle the species that will be predominant for the amino acid alanine.

CNH2

H

H3C

OH

O

CNH

H

H3C

OH

OC

NH3

H

H3C

OH

O

CNH3

H

H3C

O

O

C

NH2

H3C

H3C

O

O

The species you circled has the special name of ________________________zwitterion

At pH 7, the amine is protonated and the carboxylic acid is deprotonated, as can be predicted based on the relevant pKa vaules in Table 4.1. Use the methylammonium ion pKa value (10.64) and the acetic acid pKa value (4.76) as reference values and compare those to the pH value of 7.

O O O O

22. Rank the following from 1 to 4 with respect to relative acidity, with a 1 under the most acidic and a 4 under the least acidic molecule.

OHH

HH

OHH

HCl

OHCl

HCl

OHF

FF

4 3 2 1

Inductive effectsO O O O

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2 4 3 1

25. For each molecule, draw a circle around the most acidic H atom. Note there might be more than one on the same molecule, and you will get it correct if you circle any of the most acidic H atoms.

24. Rank the following from 1 to 4 with respect to relative acidity, with a 1 under the most acidic and a 4 under the least acidic molecule.

H3C OH OHCl

H3C OH

2 1 3 4

O O

H2O CH4 NH3 H2S

4 2 3 1

HF HBr HCl HI

H3C CH3

H3C OH

1 2 3 4

O

C C HH C C

H

HH

HH3C CH3

C

H

C

H

O

C

O

O H

H

C C

H

H

C C

O

O HCl

ClO

OH

CH

H

H

C O

O

C

H

H

H

These two are just as acidic

H

CCH

CN

H

H

C

O

OH

H

H

H