CHEMISTRY 2430
Principles of Organic Chemistry I
Exam IV - 100 points
November 12, 1999 - Dr. Howard Black


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 HCl
d. very easily oxidized
e. does not react with LiAlH4
f. incompatible with Grignard reagents
g. forms an alkene when treated with H+/D
h. reacts with NaBH4 to form a primary alcohol
i. cannot be oxidized without C-C bond fission
j. most basic of the four
k. can be formed from oxidation of a primary 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) Indicate a synthesis of any TWO (2) of the following four molecules from benzene and bromoethane. You may use any inorganic reagents you like, but all carbon atoms must come from the two starting materials provided. Please fill in the letter of your choices in the spaces provided. Work out the details of your syntheses on the paper provided. The spaces below should contain only your finished, eraser- and crossout-free synthetic schemes.
 

 
There are many correct answers to each of the syntheses; these are just examples.
 

5. (16 pts total) a. (10 pts) 1,3-Cyclopentanedione features two types of acidic protons, shown in the box. Which proton group, Ha or Hb, is more acidic? _Ha__ Explain your reasoning by drawing resonance structures of the conjugate bases for each proton type. You must use resonance structures in your answer - those without resonance structures will receive a zero without further grading.
 
 

b. (6 pts) The protons on the carbon between the two carbonyls become much more acidic if a nitro group replaces one of them (see box). Explain how it increases the acidity of Ha over the Ha in part a, using the additional resonance structure for the conjugate base made possible by the nitro group. You must show this resonance structure - no resonance structure, no credit!
 
 

__________________________________________________________________________________________

6. (8 pts) As you know, primary amines react with aldehydes/ketones to form imine (C=N) products, via water elimination, instead of the typical alcohols seen for all other nucleophilic addition reactions; this is not observed with secondary/tertiary amines or with alcohols. Why is this? Please use methylamine and acetone as your example reactants. You must include at least one mechanism in your answer, or it will not be graded.

In order for a double bond to results betweeb the carbonyl carbon and the nucleophile, the latter must have
at least two protons to lose - one during initial bond formation, and the second to form the water molecule
that is lost.  Only NH3 and RNH2 have two protons to lose:
 

7. (4 pts) Rank the following molecules in terms of decreasing acidity, i.e. most acidic to least acidic, by placing each structure's letter in the appropriate space.
 
most acidic =
__B__
__E__
__D__
__A__
__F__
__C__
 = least acidic

Bonus(5 pts, no partial credit)

A g-lactone, shown in the box below, is an example of an intramolecular ester. You already know the functional groups which go into an ester, so draw the molecule(s) that react in the presence of proton catalysis to give the lactone shown.