Chemistry 310M/318MDr. Brent Iverson1st MidtermSept. 28, 2005

NAME (Print): _____________________________

SIGNATURE: _____________________________

Please Note: This test may be a bit long, but there is a reason. I would like to give you a lot of little questions, so you can find ones you can answer and show me what you know, rather than just a few questions that may be testing the one thing you forgot. I recommend you look the exam over and answer the questions you are sure of first, then go back and try to figure out the rest. Also make sure to look at the point totals on the questions as a guide to help budget your time.

Note: You must have your answers written in blue or black pen if you want a regrade!!!!

Do not take this in red ink, as that is what we will use to grade it!

Please print the first three letters of your last name in the three boxes

Please answer the following before you begin:

Have you been to a recitation section? ____________

10

9

8

7

6

5

4

3

2

(28)

(17)

(32)

(20)

(18)

(18)

(13)

(26)

(13)

(20)

(20)

(225)

11

1

Page Points

Total

TScore

HW

CH3CO2

CH3CH2CH3

CH3CH2CHCH2

CH3OCH2CH2NH3

CH

H CH

H

HCH

HH

A) (4 pts)

B) (4 pts)

1. (6 pts) In the space provided, write the most important question in chemistry.

Signature_________________________ Pg 1 _____________(28)

C) (6 pts)

D) (8 pts) For this one you need to draw the two most important contributing sructures.

2. In the space provided, draw acceptable Lewis line structures for the following molecules. Make sure to show all formal charges and lone pairs of electrons. (Do not assume that all of the following molecules are uncharged as identifying a charged molecule is part of the question).

CHH

HCH

HC

C

H

H

H

CHH

HO C

H

HCH

HNH

HH

CHH

HC

O

OCHH

HC

O

O

Where are the electrons?

Signature_________________________ Pg 2 _____________(17)

3. (1 pt each) For the following TRUE and FALSE questions, CIRCLE ALL THE TRUE STATEMENTS. This is not meant to be tricky, but please read the statements carefully so that you do not make any careless errors. This page is worth a lot of points, so take your time.

B. Resonance contributing structures do not represent equilibrating structures, rather the hybrid (blending) of them is the true molecular representation.

C. When drawing resonance contributing structures you generally move atom nuclei and sigma bonds.

D. When drawing resonance contributing structures, you should move pi bonds (one bond of a double or triple bond) and lone pair electrons, not atom nuclei or sigma bonds.

E. Arrows drawn on contributing structures show how electron pairs move.

G. For unequal resonance contributing structures: full octets are favored, fewer charges are favored, and a negative charge on more electronegative atom (also positive charge on less electronegative atom) are favored.

H. Electrons have certain properties of particles and certain properties of waves.

J. For organic chemistry, it is best to think of electron density as waves, described by wave equations.

K. According to the valence bond approach, the atomic orbitals on each atom are combined (hybridized) first, and bonds are derived from overlap of hybridized orbitals.

M. An sp3 hybridized carbon atom has only two major hybridized orbitals, arranged in a bent geometry.

P. A sigma bond occurs when the majority of the electron density is found on the bond axis.

F. Equivalent resonance contributing structures make equal contributions to the resonance hybrid.

A. Resonance contributing structures are used when more than one structure are required to describe accurately how the electrons and charges are distributed in a molecule

I. For organic chemistry, it is best to think of electron density as particles, described by Newton's laws.

L. According to molecular orbital theory, the atomic orbitals on each atom are combined (hybridized) first, and bonds are derived from overlap of hybridized orbitals.

N. An sp3 hybridized carbon atom has only one major hybridized orbital.

O. An sp3 hybridized carbon atom has four major hybridized orbitals, arrangened in a tetrahedral geometry.

Q. A pi bond occurs when the majority of the electron density is found on the bond axis.

Signature_________________________ Pg 3 _____________(31)

4. (11 pts) 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

COH

HN

H

HHO

H

HH

CC CH

H

H

HCN

H

H

HC

OO

HH

5. For the following molecules: 1) Use the sign to indicate the direction of the bond dipole in all of the polar bonds. 2) Circle all molecules that have a measurable molecular dipole moment. 3) For the molecules you circled, to the best of your artistic ability, use an additional sign to indicate the direction of the molecular dipole moment on the left side of the molecule.

CH

HHH C

H

FHH

CF

FHH

CF

FFF

NH

HH

CF

HFF

C

O

O O

HH

(20 pts total)

Signature_________________________ Pg 4 _____________(20)

6. (20 pts) For each molecule in which contributing structures are appropriate, draw a second important contributing structure. Draw arrows on the structure on the left to indicate the flow of electrons that leads to the contributing structure you drew on the right. If the two contributing structures are not expected to contribute equally to the resonance hybrid, circle the one that makes the larger contribution. PLEASE READ THESE DIRECTIONS AGAIN TO MAKE SURE YOU KNOW EXACTLY WHAT WE WANT HERE!

C

H

H

H

C

H

H

C

O

O

C

H

H

H

C

H

H

C

O

O

Equal contributions due to symmetry

A.

CCH

H

H

OCC

H

H

H

O The structure on the righthas the negative charge onthe more electronegativeatom (O).

B.

C

H

H

H

C

H

H

N

O

O

C

H

H

H

C

H

H

N

O

O

Equal contributions due to symmetry

C.

Equal contributions due to symmetry

D.

OO O OO OOzone

Signature_________________________ Pg 5 _____________(18)

CC

CN

H

H

H

HH

H

6. (cont.) (6 pts) For this molecule in which contributing structures are appropriate, draw the next two most important contributing structures. Draw arrows on the structure on the left to indicate the flow of electrons that leads to the contributing structure you drew on the right. You do not have to circle the predominant contributing structure, as you have not yet learned which one is more stable.

CC

CN

H

H

H

HH

H

CC

CN

H

H

H

HH

H

CH3 CH2 CH CH2 CH2 C CH2

A)

B)

7. (6 pts each) Name the following molecules according to IUPAC nomenclature rules

CH3

CH2

6-Ethyl-3,6-dimethylnonane

CH3

CH2 CH3

CH31 2 3 4 5 6 7 8 9

3,6-Diethyl-8-methylundecane

1

2

3

4

5

6

7

8

9

10

11

Signature_________________________ Pg 6 _____________(18)

C)

D)

7. (cont.) (6 pts each) Name the following molecules according to IUPAC nomenclature rules

2,3,10-Trimethyl-6-(3-methylbutyl)dodecane OR 6-isopentyl-2,3,10-trimethyldodecane

1

2

3

4

5

6

7

8

9

10

11

12

12

3

4

12

3

4 5

E) For this one, write the structure that corresponds to the following IUPAC name.

1 32

(2-methylpropyl)cyclopentane OR isobutylcyclopentane

Note that when there is only one group on a cycloalkane you do not need to write the number 1.

OMolecular Insect

(You don't need to name this one!)

CH2CH2CHCH

CH2 CH3

CH2CH3

HC CH3

CH3

CH3CH2

3-Ethyl-5-(1-methylethyl)octane

1 2 3 4 5 6 7 8

1

2

8. (13 pts) In the box provided, write the hybridization state (sp3, etc.) of the atom indicated by the arrow.

C CC

CCC

HH

H

H H

C

H

H

C

H

H

C

H

NH H

C

H

H

H

Amphetamine

C C CH

H

H

CH

H

H

H CH

HC N

Acetonitrile (a solvent)

sp3

sp3

sp3

sp3

sp2

sp2sp

sp

Signature_________________________ Pg 7 _____________(13)

CC C

H

H

H

H

Hsp2

sp2

sp2

CC C

H

H

H

H

H

CC

O

CH

H

H

H

H

sp2

sp2

CC

O

CH

H

H

H

H

Signature_________________________ Pg 8 _____________(26)

9. (16 pts) You knew this was going to be on the test. In the spaces provided, indicate the type of bond, and the hybridized orbitals that overlap to form the bond. For example, one answer could be: σCsp3-H1s

C

CC

C

CC

H

H

ClH

C NC

CN

CH

HH

O

CC

CC

C

CH

H

H

H

H

H

H

Valium

σCsp3-H1sσCsp2-Osp2

πC2p-O2p

σCsp3-Nsp2

σCsp2-Csp2

πC2p-C2p

σCsp2-H1s

σCsp2-Csp2

10. (10 pts) For the following molecules: 1) in the box provided state how many DIFFERENT constitutional isomers are represented by the structures below. 2) CIRCLE all of the molecules with the IUPAC name of 2,4-dimethylhexane.

The number of different constitutional isomers is:2,4-Dimethylhexane

Same molecule

Same molecule

1

2

3

4

5

5

2,4-Dimethylhexane

1

5

3

Signature_________________________ Pg 9 _____________(13)

11. (13 pts) This page tests your understanding of important chemical terms. Make sure you read these carefully so that you do not make any silly mistakes.

A) Circle the structure with the MOST torsional strain.

H

HH

HH

H

H

HCH3

HH

CH3

H

H HHH

H

B) Circle the structure with the LEAST steric strain.

H

H3CCH3

HH

CH3

H

HCH3

HH

CH3

CH3

HCH3

HH

H

The structure you circled is given the two special names _________________________

and ___________________________ .

The structure you circled is given the special name _________________________

C) Circle the structure with the MOST angle strain.

H2C

H2C CH2

H2C

H2C CH2

CH2 H2CH2C CH2

CH2

H2C H2C

H2C CH2

CH2

CH2

H2C

D) Circle the structure with the LEAST torsional strain.

H2C

H2C CH2

H2C

H2C CH2

CH2 H2CH2C CH2

CH2

H2C H2C

H2C CH2

CH2

CH2

H2C

Eclipsed

StaggeredAnti

Signature______________________ pg 10________ (20)

12. (14 pts) Draw a Newman projection for each alkane viewed down the bond as indicated. Circle the Newman projection you drew that represents a conformation with the MOST STERIC STRAIN.

CC

H3C

CH3HH3C

HH

CH3

HHCH3

H CH3

13. (6 pts) On the following chair structures: 1) CIRCLE all of the AXIAL atoms or groups. 2) DRAW A BOX AROUND the more stable chair conformation.

CH3

HH

HH

H

H

HHH CH3

H

H

HH

CH3H

HH

HH H

H

HH

CC

H3C

HH3CH

HCH3

H

HH3CCH3

H3C H

Two gauche interactions so this one has more steric strain

The methyl group is equatorial

14. (12 pts) Now it is your turn. For the following cyclohexane derivative, draw the two alternative chair conformations, and circle the one the predominates at equilibrium. Note that you do not have to draw H atoms on the structures is you do not want to. You just need to indicate the precise placement of the methyl groups.

CH3

HH

HH

H

H

HHH CH3

CH3

H

HH3C

CH3H

HH

HH H

H

HHCH3

Both methyl groups are equatorial

Signature______________________ pg 11________ (20)

15. (8 pts) Here is an "apply what you know" problem. Fret not, it is only worth 8 pts total! If you get this correct, you will understand the basis for most of the chemistry in Chapter 16!! Remember the most important question in Chemistry! Shown below are the acetone molecule, a proton, and the hydroxide anion. Draw all the appropriate bond dipole moments on the acetone and hydroxide anion molecules for all the polar covalent bonds. Draw a BOX around the atom on the acetone molecule that is most likely to interact with the proton, and draw a CIRCLE around the atom on the acetone molecule most likely to interact with the hydroxide anion. Read these directions again to make sure you know what we want!

CH

H

H

C

O

C

H

H

H

O H H

The oxygen atom has a partial negative charge and will therefore interact with the positively-charged proton (opposite charges attract), whereas the carbon atom has a partial positive charge and will interact with the oxygen atom of the negatively-charged hydroxide anion. You will soon learn that species having a strong area of partial or full negative charge are called nucleophiles, and they react with atoms on molecules having partial positive charge (called electrophiles). This explains 95% of the chemistry you will see for the rest of your Organic Chemistry courses!

Acetone

Hydroxideanion