Warm-up Exercise for August 30, 2000

Due at 7:30 AM on 8/30/2000

1. Use a pen(cil) and paper to draw as many isomers of C₅H₁₂ as you can.Ý How many did you draw?Ý Describe each structure in words.

2. ¹³C NMR spectroscopy is used to explore the carbon skeletons of molecules.Ý The position of the signal is dependent on the electron density around the carbon.Ý In organic chemistry we indicate electron density using d+ and d-.Ý The larger the dipole, the larger the change in electron density.Ý Signals for carbons attached to silicon usually come at 0 ppm.Ý Those attached to other carbons usually come at 15 ppm.Ý When a carbon is attached to an oxygen, the signal is usually at 50 ppm.Ý Where would a carbon attached to a nitrogen come.Ý Explain your answer.

3. An unknown compound was analyzed using combustion analysis and mass spectroscopy.Ý Combustion analysis showed the compound has an empirical formula of CH₂.Ý Mass spectroscopy showed a molecular ion of m/z=56.Ý The molecular formula for this compound is:

a. CH₂

b. C₃H₄O

c. C₄H₈

d. There isn't enough information to answer this question.

4. If you would like to make any comments about today's lab, your reading assignment, or what we need to spend more time on, here's your chance.