Chemistry Reference
In-Depth Information
Tutorial examples
Q
1 Ephedrine is a naturally occurring drug useful in the
treatment of asthma. Its structure is shown in Figure 1.5.
(a) Classify ephedrine as acidic, basic or neutral.
(b) Using your answer to part (a) as a guide suggest a
simple way in which the water solubility of the drug could be
increased.
OH
H
CH
3
N
CH
3
H
H
Figure 1.5
The structure of ephedrine, pK
a
9.6.
A
1(a) Ephedrine is an alkaloid produced by Ephedra (the
Ma
huang
plant). It was widely used for the relief of bronchospasm
associated with an attack of asthma. The drug has been super-
seded in recent years by safer, more effective bronchodilators such
as salbutamol and terbutaline. The diastereoisomer of ephedrine,
pseudoephedrine, is widely used in cough mixtures as a decon-
gestant. Ephedrine is a secondary amine and, because the lone pair
of electrons on the nitrogen can react with H
ions, is basic in
solution (Figure 1.6).
OH
OH
H
H
CH
3
CH
3
+ OH
-
+ H
2
O
N
+
N
CH
3
H
H
CH
3
H
H
H
Figure 1.6
Reaction of ephedrine with water.
(b) The water solubility of the drug could be increased by
forming a salt with a mineral acid such as hydrochloric acid to give
ephedrine hydrochloride (Figure 1.7).
