CHEMISTRY 2430
Principles of Organic Chemistry I
Exam IV - 100 points
Nov. 16, 1998 - Dr. Howard Black
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Name ________________KEY_________________________

Throughout this exam, give answers only in the provided spaces (boxes or lines). Answers not in these spaces will not be graded, even if correct.

1. (12 pts) Give acceptable names for the following compounds, being sure to address alkene geometry and R/S configuration where appropriate.

2. (14 pts) For each of the following four molecules, list the properties from the list on the right which best describe it. Each item on the list can be used as often as necessary, or not at all. DON'T GUESS!!
 
a. contains no sp2 carbons
b. reacts with Ag(NH3)4+ (Tollens' reagent)
c. forms a salt with NH3
d. very easily oxidized
e. does not react with LiAlH4
f. incompatible with Grignard reagents
g. lowest vapor pressure of the four
h. reacts with NaBH4 to form an alcohol
i. most volatile of the four
j. most basic of the four
k. can be formed from oxidation of a 1o alcohol

3. (30 pts) Complete the following reactions (provide either the starting molecule, the reagent(s), or product(s). If more than one product is produced, draw them all. If one product predominates, circle it.

4. (16 pts) Provide a synthesis of any TWO (2) of the following four molecules from the indicated starting materials. You may use any inorganic reagents you like, but all carbon atoms must come from the starting material provided. Please fill in the letter of your choices in the spaces provided on the following page.



5. (16 pts) Explain the following observations.
 

a. The A protons in the box are much more acidic than the B protons. Your explanation must include resonance structures.

The conjugate base from the loss of HB has two resonance contributors, while that from HA has three, making it more stable. Thus, HA are more acidic than HB.


b. Formaldehyde, H2C=O, is carcinogenic due to its ability to methylate the nitrogen atoms in DNA. Using the model reactions in the box, provide the identity of A and B and illustrate the mechanisms of their formation.

6. (8 pts) Rank the following molecules from most acidic to least acidic, by placing the letters corresponding to each molecule in the appropriate rank supplied below.

1. __C_ 2. __G_ 3. __I__ 4. __D_ 5. _F__ 6. _B__ 7. __H_ 8. _E__ 9. __A_

Most acidic
Least acidic

7. (4 pts) All reactions in organic chemistry can be explained in terms of steric effects and electronic effects. Please explain the greater reactivity of aldehydes over ketones toward nucleophilic attack, and use both of these effects in your answer.

Steric reason: Aldehydes, with H rather than R attached to the carbonyl, are less congested at the point of attack

Electronic reason: The R group in ketones is electron-releasing relative to the H in aldehydes, so the carbonyl in ketones is less positive, making it less attractive to nucleophiles


Bonus(5 pts, no partial credit)
 
A common method for the a-bromination of simple ketones and aldehydes involves simply dissolving the substrate in acetic acid and treating it with bromine. Provide the mechanism of this straightforward reaction, as illustrated in the box.