Problem Set 1
Chapters 1 and 2, Structure, Bonding, Reactivity
Due: Monday, September 13, 2010
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. The chemical structures shown
below all occur in nature. They have also been made
(synthesized) by chemical means from simpler organic
compounds in this department over the past 40 years.
[See
the background on the website homepage.] You will learn
about Classes of Compounds one class at a time 40 years.
They will be for the most part mono-functional compounds.
All of the compounds shown below are multi-functional
compounds. a) Identify the Class of Compound of the
functionality present with in each of the circles. Print
this page and use it to designate answers. [See the
inside front cover of your textbook for Classes of
Compounds, Functional Groups and
Abbreviations.] b) You should have identified two
alcohols [ROH, where R = alkyl (aliphatic), not
aryl (aromatic)]. Of these two alcohols, one is said to
be primary, the other tertiary. Why? Is there another
primary alcohol in the structures? Another tertiary alcohol?
Are there any secondary alcohols?
2. Draw resonance structures (if they exist) for the following compounds. Include all formal charges.
3. 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. The pKa table will be of help.
4. Arrange the eight acids and conjugate acids in
problem #3 in order of increasing acidity (decreasing
pKa).
5. Draw an orbital picture for the alkyne,
2-butyne (CH3CCCH3). Identify σ- andπ-bonds
and hybridization.
6. A normal alkane, CnH2n+2, is found to have a
vapor density of 2.52 mg/mL at 250oC and 720 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.)