Chem 220 - Organic Chemistry

Problem Set 1

Chapters 1 and 2, Structure, Bonding, Alkanes

Due: Monday, September 19, 2011


 

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. Dalton postulated that in a molecules comprised of two different atoms, the simplest one in the series would be binary. While this rule applied to CO and CO2, it did not apply to the pair, water and hydrogen peroxide. Thus, water, according to Dalton, was OH. The Rule of Greatest Simplicity, which was at odds with Gay-Lussac's Law of Combining Volumes of Gases that demonstrated the volume of hydrogen produced upon electrolysis of water was twice that of oxygen, was dismissed by Dalton as a faulty result. 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 (Prout's Hypothesis), 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 each of the non-hydrogen atoms in each of the following structures.

4. Name the alkane shown here (dynamic view). [Read the Jmol instructions on how to manipulate the structure.] For a static view, click here.

5. Determine the heat of combustion of n-decane by estimating its heat of formation. For assistance, read about Hess's Law and utilize the Heats of Formation Tables in the Thermochemistry Module of the Study Aids. [Hint: Notice the pattern in the heat of formation of n-alkanes as they increase in mass by one methylene (-CH2-) group.] Show work!