(initial version published Aug 20, 2008)
Once you get used to them, you may find that the problems
in your textbook have a game-like quality. If you make the right mental
“moves”, you will nearly always solve the problem. It’s a nice way to
get started thinking about organic chemistry, but not terribly realistic.
Modern organic chemists spend most of their time working on problems that can’t
be solved just by making the right moves. These problems are both scientific
and technological and if we ever solve them, we will change how the entire world thinks and lives.
The following unsolved problems (more realistically, “unfinished
tasks”) happen to be four items that strike me as really important. Other chemists are
sure to both agree and disagree, and if you would like to have some fun
tweaking a chemist (and also learn something in the process), ask him/her what the four
most important unsolved problems are. Maybe you already have some ideas of your
own? If you do, post them as a comment.
1. Discover new molecules. Every living organism is a
chemical factory, churning out compounds for fuel, construction, waste,
communication, you name it. “Natural products” is the branch of organic
chemistry that is devoted to the discovery of new naturally occurring
compounds. There have been many headlines about the accelerating loss of
biodiversity, but there’s a second point that’s just as important: every time
we lose an organism, we lose the entire ensemble of chemicals unique to that organism.
Some lucky chemist may accidentally make one or two of these compounds in a lab
somewhere, but the opportunity to see what these compounds do in their natural
habitat will be lost.
2. Make new molecules. “Synthetic” chemists have
made over 10 million organic compounds in the past century. As impressive as
that number is, it is just a tiny fraction of what is possible. The only way to
really know what is possible (and what it might be like) is to make something
new and study it. The 1964 edition of Cram and Hammond, a popular textbook of
that period, displayed 29 drawings of unknown organic molecules in its inside
cover. Six years later, the next edition divided these into “synthesized
after 1964” (15 molecules) and “not yet synthesized” (14 molecules).
Of course, making new compounds is more than an intellectual exercise.
Synthetic chemists are also trying to discover compounds that can solve genuine
problems: medicines, lightweight electronic devices, solar energy converters,
and so on.
3. Learn to make molecules that are ‘benign by design’.
These words describe one of the fundamental goals of “green” chemistry:
making compounds that are inherently safe to use and throw away. Biological
organisms are experts at green chemistry. They rely on biodegradable substances
called enzymes to accelerate and control chemical reactions, they do their work
at or near room temperature, and they rely on readily available raw materials:
sunlight, carbon dioxide, water, and some other items. Traditional synthetic
chemists, on the other hand, have mostly been interested in the final compound,
with safety, especially ‘downstream’ safety, taking a back seat. Another
important goal of green chemistry is sustainable chemical manufacture. Biological
organisms rely on renewable resources. Chemical manufacturers have mainly
relied on petroleum. As we learn more about the importance of chemical hazards
and limited resources, we need chemists to redesign chemical technology from
top to bottom, and new technologies require new scientific discoveries.
4. Develop a reliable molecule-based theory of chemical and physical
phenomena, especially molecular structure-property relationships. As you study organic
chemistry, you will find that chemists (especially chemistry teachers) are more than ready to provide
explanations for all sorts of chemical phenomena. However, if you dig just a
little deeper, you will find that many of our standard explanations turn out to
be “Just So” stories, a comfortable way to fit some facts together, and are neither
complete nor even true. We rely on very “immature” theories to explain chemical
and physical phenomena.
One easy way to
highlight these weaknesses is to ask a chemist to design a substance with a
particular desired property or that can perform a particular function. You might, say, ask a chemist to design a
biodegradable organic compound that conducts electricity as efficiently as
copper. The chemist will tell you that is impossible, i.e., it isn’t impossible
that such a compound exists, it is simply impossible to design one given our
current understanding. OK, let’s aim for something simpler. How about a solid organic
compound that melts at 88 oC and is blue. That’s “impossible” too.
Clearly we don’t really understand how the world works. We know that a molecule’s
structure determines its properties, but we usually can’t predict what those
properties will be. To put it another way, we don’t have a sophisticated or
deep grasp of structure-property or structure-function relationships.