Page 15 - Encyclopedia of Chemical Compounds 3 Vols

Reader’sGuide

compounds, they usually use only the official IUPAC name
for a compound since that name leaves no doubt as to the
substance about which they are talking. In some cases, a
compound may have more than one official name, depending
on the set of rules used in the naming process. For example,
0
1,1 -thiobis[2-chloroethane] is also an acceptable name for
mustard gas. The ‘‘Other Names’’ section of each entry
lists both the systematic (IUPAC) and common names for a
compound.
Many compounds also have another kind of name, a
brand name or trade name given to them by their manufac-
turers. For example, some trade names for the pain killer
acetaminophen are Panadol TM , Tylenol TM , Aceta TM , Gena-
TM TM TM
pap , Tempra , and Depacin . The symbol next to each
name means that the name is registered to the company that
makes the compound. Trades names may be mentioned in the
Overview or Uses sections of the entry for each compound.

Chemical Formula: A chemical formula is a set of sym-
bols that tells the elements present in a compound and the
relative numbers of each element. For example, the chemical
formula for the compound carbon dioxide is CO 2 . That for-
mula tells that for every one carbon atom (C) in carbon
dioxide there are two atoms of oxygen (O).

Chemists use different kinds of formulas to describe a
compound. The simplest formula is a molecular formula.
A molecular formula like CO 2 tells the kind and relative
number of elements present in the compound. Another kind
of formula is a structural formula. A structural formula
provides one additional piece of information: The arrange-
ment of elements in a compound. The structural formula for
methanol (wood alcohol), for example, is CH 3 OH. That for-
mula shows that methanol consists of a carbon atom (C) to
which are attached three hydrogen (H) atoms (CH 3 ). The
carbon atom is also joined to an oxygen atom (O) which, in
turn, is attached to a hydrogen atom (H).
Structural formulas can be written in a variety of ways.
Another way to draw the structural formula for methanol, for
example, is to show where individual bonds between atoms
branch off other atoms in different directions. These struc-
tural formulas can be seen on the first page of nearly
all entries in Chemical Compounds. In a third type of struc-
tural formula, the ball-and-stick formula, each element is

xiv CHEMICAL COMPOUNDS