Chem 220 - Organic Chemistry

Problem Set 1

Chapters 1 and 2, Structure, Bonding, Alkanes

Due: Monday, January 28, 2013


 

John Dalton

(1766-1844)

John Dalton's formulation of an Atomic Theory in the first decade of the 19th century provided a theoretical basis for understanding chemical behavior. In addition to defining the Law of Multiple Proportions, he also formulated the Rule of Greatest Simplicity, which held that water was a binary compound, OH. (Note: Dalton did not use our modern symbols, which came to us from Berzelius, but rather circles that were distinguishable from one another.) Dalton established the combining masses of H to O in water as ~1:6. This ratio was later refined to 1:8. The Rule of Greatest Simplicity, which was at odds with Gay-Lussac's Law of Combining Volumes of Gases, did not lead to a correct formulation for the atomic composition of water. Moreover, although there was agreement regarding the combining masses of atoms in the first half of the nineteenth century, there was disagreement as to the unit mass of the common atoms encountered in organic chemistry: hydrogen (1), carbon (2x6 or 1x12), oxygen (2x8 or 1x16). Since hydrogen was the lightest of the elements, it was assigned a mass of one, a notion that is unrelated to today's mass of hydrogen owing to the presence of a single proton in the hydrogen nucleus. Berzelius's proposal of a mass scale based upon O = 100 would have worked as well.

For a Brief History of Organic Chemistry (PowerPoint), click here.

 



1. Identify the functional groups in the red circles. The front inside cover of your text will be of use. Complete this problem on a copy of this page and attach it to your homework.

 2. Draw resonance structures (if they exist) for the following species. Include all formal charges.

3. Identify the hybridization (sp, sp2, sp3) of the carbons, oxygen and nitrogen in escitalopram in problem #1 above. Re draw the structure and indicate each site with an arrow.

4. For each of the following acid/base reactions, provide appropriate equilibrium arrows reflecting the position of the equilibrium. For the right side of the equilibrium, provide the conjugate acids and bases. Estimate the equilibrium constant for each reaction.  For help on this topic, click here.

 

5. Arrange the eight acids in problem #4 in order of increasing acidity (decreasing pKa).

6. Draw an orbital picture of vinylacetylene, (CH2=CHCCH). Identify σ- and π-bonds and hybridization.

7. A normal alkane, CnH2n+2, is found to have a vapor density of 2.16 mg/mL at 100oC and 700 mm pressure. Using the ideal gas law, determine the structure of the alkane. (In the early 19th century, the vapor density of an unknown liquid was compared to the vapor density of air to determine the liquids molecular weight.)