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CH234, Exam 2 Key , Spring 2006
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Name
This exam consists of several parts of unequal difficulty. Look over the whole exam right now, and start on something you know well. If you don’t know something, skip it, and come back to it later. Use your time wisely.
Keep Your Eyes On Your Own Paper!
Grading Summary
Page 2. ______(30)
Page 3. ______(10)
Page 4. ______(25)
Page 5. ______(20)
Page 6. ______(15)
Bonus. ______( 5 Maximum)
Total ______(100)
1. Give IUPAC names for the following structures.
a./ The highest priority group is the amine. The longest chain bonded to the amine is four carbons, so it is a butanamine. The amine is attached to the second C, the phenyl is attached to the first C, and the methyl is attached to the N, so the name is
N-methyl-1-phenyl-2-butanamine.
b.
/ This is a six-carbon aldehyde, so it is a hexanal. There are three methyls and a hydroxy attached, so the name is 3-hydroxy-2,2,4-trimethylhexanal.
c.
/ This is an ester. A three-carbon group is attached to the single-bonded oxygen, so the first word is propyl. There is a seven-carbon piece that contains the carbonyl, that also has a C=C, so this piece is a heptenoate. The C=C starts at 5, and it is cis, so the complete name is
propyl cis-5-heptenoate.
d.
/ There is an amide attached to a benzene ring, so this is a benzamide. There is a cyclopentyl group on the N, and an amino group attached to carbon 3 of the benzene ring, so the name is
3-amino-N-cyclopentylbenzamide.
e.
/ The longest chain is the three-carbon chain containing the carboxylic acid, so it is a propanoic acid. There is a cyclopropyl group attached to the second carbon, so the name is 3-cyclopropylpropanoic acid.
2. Physical Properties
a. Which of the following compounds is more water-soluble? Explain why. Show any attractions of the compounds for water.
Benzene Pyridine
C-H’s are not partially positive, since C & H are very close in electronegativity. Therefore, benzene is not attracted significantly to water. The N of pyridine is partially negative, so it attracts a partially positive H of water. This makes pyridine somewhat water-soluble.
b. One of the following compounds has a significantly lower boiling point than the other two. Which one is it? Explain why its boiling point is much lower.
The first molecule doesn’t have a partially positive H, since all of its H’s are bonded to C. Therefore, it cannot hydrogen-bond with other molecules of itself. The other molecules have either an O-H or an N-H, so they can hydrogen-bond to other molecules of themselves. The energy of the hydrogen-bond must be overcome to separate molecules, so the last two molecules have higher boiling points.
c. Circle the most acidic compound in the group below.
Carboxylic acids are much more acidic (Ka about 10-4) than water (Ka = 2 * 10-16). Amines are bases, so they are incredibly weak acids.
3. Give the major organic product(s) of each of the following reactions.
a. Carboxylic acids and amines produce amides and water when heated.
b. Hydrolysis of an ester produces a carboxylic acid and an alcohol.
c. Ketones + alcohols produce an acetal + water.
d. Reduction of a ketone produces an alcohol
e. Oxidation of an aldehyde produces a carboxylic acid.
3. Give the product(s) of each of the following reactions.
a. Amines are bases, so they react with strong acids to make salts.
b. Carboxylic acids react with hydroxide bases to produce salts and water.
c. Amine salts are weak acids, so they react with strong bases to form amines.
d. Draw the structure of two repeating units of the polymer (Kevlar, in bullet-proof vests) formed by heating the following two compounds.
When carboxylic acids are heated with amines, amides are formed. Therefore, a diacid and a diamine can form a polyamide. I showed you nylon in class. Kevlar was in the book.
4. Circle and label each occurrence of the following functional groups in the structure below. Some may be used more than once, and some not at all.
Amine Carboxylic Acid Ester Phosphoric Ester
Amide Aldehyde Ketone Phosphoric Anhydride
Bonus: What compounds would you react together to make the following molecule, which is found in raspberries? What catalyst would you use?