Chem 220: March 2012

Friday, March 9, 2012

Practice Final Exam 2009 Answers

Practice Final Exam 2010 Answers

A few mistakes on this answer key:

1. The haworth structure for fructofuranose should have CH2OH instead of H on the first carbon immediately right of the oxygen at the top of the ring.

2. On page 4 number 3a, the extended structural formula should include two lone pairs of electrons on each oxygen.

3. On page 4 number 3c, in the third step of the mechanism the CH3-CH2-O molecule should not directly remove the H from from the carboxyllic acid. You should first add a hydrogen to the CH3-CH2-O to make ethanol. Do this by drawing an arrow from the negatively charged oxygen to a hydrogen on the water molecule. This step will produce ethanol and -OH. Then use the -OH molecule to remove the H from the carboxyllic acid. Do this by drawing an arrow from -OH to the H on the carboxyllic acid.

4. On page 6 number 5b iii, the answer should be 3-methyl-6-nonanol.

(Disclaimer: I didn't make this answer key...)

Practice Final Exam 2011 Answers

Here's the answer key to the 2011 final exam. One thing to note: One page 4 where the resonance structures for CO3 are drawn out, you should draw arrows showing where the electrons move to make the next resonance structure. (i.e. draw an arrow from the electrons on one of the singly bonded oxygens showing the formation of a double bond, and draw a second arrow from the double bond forming a lone pair on the oxygen)

Quiz Section Exercise: Esterification

Oops! That last problem on this worksheet isn't finished! If you came to quiz section, then we did it correctly in quiz section. Notice, the hydrogen is missing from the wrong oxygen. You have to do two more steps to finish this problem. The first step is where negative oxygen takes a hydrogen from water. The second step is where the hydroxide ion takes off the hydrogen from the carboxyllic acid. Sorry!