Chemistry Reference
In-Depth Information
a very large library, such as the Biblioth
`
que Nationale de France, contain all
together about 10
13
letters, whereas in the body of a man there are about 10
28
atoms: one million billion times more!
Atoms, like letters, are indispensable, but they do not have much meaning by
themselves. As in a language, words are the smallest units with a meaning; in
chemistry, molecules are the smallest entities that can play a function: they are
indeed the smallest entities of matter that have distinct shapes, sizes and properties.
Therefore, like words, molecules contain specific pieces of information that can be
seen as “the meaning” of a molecule.
Both words and molecules can have a strong impact on our life. Both the word
“rose” and the molecule responsible for the perfume of a rose give us a pleasant
sensation. Words and molecules can be sweet, bitter, light, heavy, sour, cutting.
There are words and molecules that can save or kill a life.
There is another important analogy between language and chemistry. The mean-
ing of a word depends not only on the number and types of letters by which it is
formed, but also on the order of the letters. For example, in Italian by using 2a, 1g, 1i,
1l, 1o, 1r, 1t, 1v we can write two words with very different meanings,
giravolta
(complete turn) and
travaglio
(torment). Analogously, the same atoms, namely 2C,
6H, 1O, constitute the molecules of methyl alcohol and dimethyl ether that have the
same formula, C
2
H
6
O, but very different properties because of the different order in
which the atoms are linked together. Both words and molecules can be disassembled
and then reassembled to give rise to other words or molecules. The Latin poet
Lucretius was a master in doing that with words [
2
]. But Nature is much better.
Our body is a book in which some molecules are continuously erased and others
written: our skin is fully replaced in a month, our liver is renewed every 6 weeks.
The field of chemistry is much broader than the field of any language. In Italian
we have about 160,000 words, whereas at least 5 million types of molecules can be
found in Nature and about 15 million types of artificial molecules have been
synthesized by chemists. Leonardo da Vinci did not know chemistry; nevertheless,
his sentence “Where nature finishes producing its species, there man begins with
natural things to make with the aid of this nature an infinite number of species” [
3
]
is quite appropriate to comment the outstanding development of chemistry.
Chemists, indeed, started as explorers of Nature, but very soon they also became
inventors and today they continue to play such dual role. As a consequence,
chemistry is at the same time a book that we can read and a collection of white
sheets that we can write on. A large part of the book has not yet been read
(undiscovered natural molecules and processes) and the number of white sheets
to be written on (artificial molecules and processes) is endless.
3 Beautiful Molecules
Molecules of nearly any shape have been synthesized in recent years. Instead of
using conventional chemical names, chemists often call these molecules by
names derived from the similarity of the molecular shapes to those of objects
