Problem Set 1
Chapters 1 and 2, Structure, Bonding, Reactivity
Due: Monday, September 14, 2009
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, which demonstrated that
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. a) Identify the four
functional groups in azithromycin marked by arrows. |
3. For each of the following acids or bases, identify the corresponding conjugate base or acid, whichever is appropriate. The pKa table may be of help.
a) LiNH2b) acetic acid
c) KOCH3
d) CH3CH2MgBr
e) C2H5OH
4. Arrange the acids and conjugate acids in
problem #3 in order of increasing acidity (decreasing
pKa).
5. Draw an orbital picture for the monomer,
vinylacetylene (CH2CHCCH). Identify π-bonds and
hybridization.
6. A normal alkane, CnH2n+2, is found to have a
vapor density of 1.78 mg/mL at 300oC and 740 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.)