Dr. Glaser's "Chemistry is in the News"
To Accompany Bruice, Organic Chemistry, 3/e.
Chapter 7. Reactions of Dienes
Editorial Comments
Jean-Marie Lehn, the Nobel prize winning French chemist from Strasbourg, is one of the pioneers in the area of "supramolecular chemistry". In his recent book "SUPRAMOLECULAR CHEMISTRY - Concepts and Perspectives", Lehn defines supramolecular chemistry as the "chemistry beyond the molecule". According to Lehn, it is the goal of supramolecular chemistry to gain control over the intermolecular non-covalent bond. Supramolecular chemistry is concerned with the entities of higher complexity than molecules themselves. Just how far should this complexity go? Can one make functioning devices in which the parts are molecules? Many scientists in the world are working on the answer to this question. Devices on the molecular scale would be of sizes that are in the nanometer range (10 Angstrom is 1000 pm or 1 nm). Hence, the quest for molecular scale devices is the domain of what has become known as "nanotechnology". Check out NanoTechnology Magazine for many interesting articles. Keep your eyes open for articles on advances in nanotechnology, that is where much of the innovation in future will be coming from!Questions
Question 1:
Take look a your Swatch. A
fine piece of Swiss watch making. Let's use this example to gt an idea of
scale. A swatch is a fine machine and contains parts as small as 0.1 mm.
How many magnitudes of scale are there between this technology and
nanotechnology?
Answer 1:
0.1 mm = 10-4 m. 1 nm = 10-9 m. 5 magnitudes or a
factor of 10,000.
Question 2:
What kinds of wires are discussed in the article and what bonding
characteristic do they all have in common?
Answer 2:
The simplest wires are those containing alternating single and double
bonds (=CH-CH=CH-CH=CH-) and alternating single and triple bonds
(-CC-CC-CC-). Some of the more complicated wires also contained benzene
or thiophene. The one bonding characteristic that all the wires
have in common: Conjugated multiple bonds!
Question 3:
Would it be possible, at least in principle, to make wires that are
cumulenes (=C=C=C=C=) or
contain segments of cumulenes (=C=C=CH-CH=C=C=C=)?
Answer 3:
Yes, it should be possible to use cumulenes as molecular wires. For a
molecule to function as a wire, the necessary condition lies with the
potential for conjugation along the entire wire. Note that in extended
cumulenes, every double bond conjugates with every double bond that is one
double bond away! An extended cumulene contains two (red and blue)
conjugated systems: ...C=C=C=C=C=C=...
Question 4:
In the article, dimensions are discussed in nanometers. It is said, for
example, that 300 nanometers is the limit to the size of structures that
can be generated with the principles of current chip fabrication
technology. How many -HC=CH- does one need to make a wire that is about
300 nm long? (Note: 1 Angstrom = 100 pm; 1 nm = 1000 pm)
Answer 4:
Based on the dimensions of ethene, one can estimate that each -HC=CH- unit
takes up about 2.25 Angstrom or 225 pm. Since 300 nm equals 300,000 pm,
we would need a wire that contains 1333 units.
Chemistry
& Society.
Question 5:
The Office of the President of the United States published a report in
the first quarter of 2000 asking for a
National Nanotechnology Initiative: Leading
to the Next Industrial Revolution (NNI). President Clinton stressed
that "some of our research goals may take 20 or more years to achieve,
but that is precisely why there is an important role for the federal
government." Discuss the significance of NNI and argue whether and why
such efforts warrant taxpayer support.