Chemistry Reference
In-Depth Information
2
The Organic Chemistry
of Surfactants
In order to understand the relationship between the surface activity of a given
material and its chemical structure, it is useful to have a handle on the chemistry
of the individual molecular components that produce the observed phenomena. The
following discussion introduces the basic chemical principles involved in common
surfactants, ranging from basic raw materials and sources to the chemical group
combinations that result in observed surface activity.
The chemical compositions and synthetic pathways leading to the formation of
surface-active molecules are limited primarily by the creativity and ingenuity of the
synthetic chemist and the production engineer. Therefore, it is practically impos-
sible to discuss all potential chemical classes of surfactants, including their prepa-
rations and subtle variations. However, the majority of surfactants of academic and
technological interest can be grouped into a limited number of basic chemical types
and synthetic processes.
The chemical reactions that produce most surfactants are rather simple and easy
to understand for anyone surviving the first year of organic chemistry. The chal-
lenge to the producer lies in the implementation of those reactions on a scale of
thousands of kilograms, reproducibly, with high yield and high purity (or at least
known levels and types of impurity), and at the lowest cost possible. With few
exceptions, there will always be a necessity to balance the best surfactant activity
in a given application with the cost of the material that can be borne by the value
added to the final product. The challenge to the ultimate user is to understand the
chemical, physical, and biological requirements that a candidate material must meet.
Before discussing specific details of surfactant types and possible synthetic path-
ways, it may be useful to introduce some of the many reactions that can produce
surfactant activity in an organic molecule. In that way, the reader can begin to see
some of the basic simplicity of surfactant science underlying the imposing variety
of structural possibilities.
The chemical structures having suitable solubility properties for surfactant acti-
vity vary with the nature of the solvent system to be employed and the conditions
of use. In ''standard'' surfactant terminology, the ''head'' refers to the solubilizing
