Chemistry Reference
In-Depth Information
FORMULAE
Empirical formula — simplest ratio of atoms in a molecule
Molecular formula — actual number of atoms in a molecule
Structural formula — shows the order of atom linkage
Example: The compound “adipic acid” is used to make nylon and as an
acidulant in “Jello”
Empirical formula: C
3
H
5
O
2
Molecular formula: C
6
H
10
O
4
Structural formula:
H
H
H
H
O
O
HO
C
C
C
C
C
C
OH
HO
2
CCH
2
CH
2
CH
2
CH
2
CO
2
H
H
H
H
H
O
O
HO
2
C(CH
2
)
4
CO
2
H
HO
C
CH
2
CH
2
CH
2
CH
2
COH
COOH
HOOC
The intersection of lines in the above structural formula is understood to
represent a
−
CH
2
−
There are so many isomers possible in organic chemistry that molecular
formulae alone are essentially useless. Structural formulae are the most
useful, but, for ease in printing or writing, generally every bond is not shown.
For example, the butanes can be written as CH
3
(CH
2
)
2
CH
3
for n-butane and
CH
3
CH(CH
3
)CH
3
for isobutane. Various ways of depicting the structural for-
mula of adipic acid are shown above. Although these formulae may appear to
differ, careful study shows that they all represent the same compound.
