Soddy, Frederick 249wide-ranging applications from anticancer drugs to nan-
otechnology.
Fire was also essential for mankind’s discovery and
exploitation of the elements of copper, gold, silver, tin, lead,
iron, and mercury, and, by trial and error, their alloys such
as bronze (copper and tin), pewter (tin and lead), and steel
(iron and carbon). Since the 18th century, scientists have
discovered more exotic metals and created novel alloys,
some of which are important industrial catalysts—acceler-
ators of chemical reactions. Two of the largest scale uses
of catalysts are petroleum cracking, optimization of fuel
production, and hydrogenation of vegetable oils (hardening)
for oleomargarines. Other alloys act as semiconductors
used in integrated circuits and superconductors such as
those used in magnets for medical magnetic resonance
imaging (MRI).
Oils and fats have been important throughout human
history not only for food, but also as lubricants, polishes,
ointments, and fuel. The reaction of oils and fats with alkali
(saponification) produces soap (salts of fatty acids) and
glycerin. This chemical process was known to the Romans
and continues to be of significant commercial importance.
Today, tens of thousands of tons of soap are produced
annually from tallow and plant oils. Tallow is a by-product of
the meat industry, while the principal plant oils are depen-
dent on extensive plantations—palm and palm kernel oils
from Indonesia, Malaysia, and India, and coconut oil from
the Philippines and Brazil. Twentieth-century chemists
designed more effective synthetic, crude-oil-based surface-
active agents (surfactants, e.g., sodium linearalkylbenzene-
sulfonate or LAS) for fabric, household, and industrial
cleaning applications, and specialty surfactants to meet the
needs of consumer products industry such as milder skin
and hair cleansers.
The surface-active properties of dissolved soaps and
surfactants are attributed to their amphipathic structure,
having both hydrophilic (water liking) and hydrophobic
(water disliking) parts. In solution, surfactants condense
at interphases, with the hydrophilic end in solution and
with their hydrophobic tails aligned away from the solu-
tion. As a result, surfactants change the solution surface
properties, lowering the surface tension and improving
wetting and spreading. Early studies of surfactant mono-
layers provided insights into the surfactant molecule size
and shape and the intermolecular forces that influence
molecular packing. In the bulk solution, surfactants aggre-
gate to form microscopic micelles when the so-called crit-
ical micelle concentration (CMC) is exceeded. Typically,
the micelles initially assume consistent spherical aggre-
gates. As the concentration of surfactants increases, the
micelles may also assume the shape of rods and plates or
disks. Under the proper conditions, some surfactants may
form vesicles, cell-like spherical structures consisting of a
surfactant bilayer “skin” separating an internal phase
from the surrounding bulk solution. Chemists design spe-
cial surfactants and control formulation compositions in
order to exploit these phenomena in a broad range of
novel products and applications.
Scientists have long recognized that specific molecu-
lar interactions and aggregation phenomena are crucial in
biological systems. Lipid bilayers are essential for forming
the complex cell membrane, while hydrogen-bonding
interactions between nucleic-acid base pairs give rise to
the double helical or twisted ladder structure of DNA,
arguably the most important discovery of the 20th century.
More importantly, the specific hydrogen bonding in DNA is
also responsible for the ability of multiplying cells to pre-
cisely reproduce their genetic code. Modern scientists
have learned how to mimic the cell’s ability to replicate
DNA, a technique now commonly used in forensics for
DNA matches. Molecular interactions also determine the
three-dimensional structure of enzymes and other biologi-
cally important proteins and thereby their function. Phar-
maceutical chemists have long designed drugs that target
proteins in disease-causing organisms to cure infections.
Recently, scientists discovered that short-chain proteins,
called prions, can catalyze the protein misfolding that
causes BSE or “mad cow disease.” They now hope that
further research may lead to a cure for BSE and other ail-
ments caused by misfolded proteins such as Alzheimer’s
and Parkinson’s.
Chemists are now venturing to exploit their knowledge
about molecular interactions to design molecules that can
be controlled to self-assemble into novel structures. Some
scientists hope to create a set of molecular building blocks
to construct “molecular machines,” while others are
designing nanostructures with electrical properties useful
for creating the next generation of computer chips. A few
scientists even dare to attempt to create “artificial life.”
The world of chemistry is all around us. Modern sci-
ence has deciphered many of nature’s chemical mysteries,
but there are still many more to be discovered, sometimes
in the most common but overlooked places. These few offer
only a glimpse at the important role chemistry plays in sci-
ence, its contributions to mankind, and the opportunities
available to the curious.—Karl F. Moschner, Ph.D.,is an organic
chemistry and scientific computing
consultant in Troy, New York.