Chemistry Reference
In-Depth Information
5.2.3 Synthesis of Zwitterionic Surfactants
When a single surfactant molecule exhibits both anionic and cationic dissociations
it is called zwitterionic [42]. The main characteristic of zwitterionic surfactants is
their dependence on the pH value of the solution in which they are dissolved. In
acid solutions, the molecule acquires a positive charge and behaves like a cationic
surfactant, whereas in alkaline solutions it becomes negatively-charged and behaves
like an anionic one [43].
The majority of rosin-based zwitterionic surfactants are amino acids, including
amino carboxylic acids, amino sulfonatic acids and amino phosphonic acids.
Cui and co-workers reported three new betaine-type amphoteric surfactants,
N
-(2-dehydroabietyloxy)ethyl-
N
,
N
-dimethyl carboxymethyl betaine,
N
-
(2-dehydroabietyloxy)ethyl-
N,N
-dimethyl sulfoxypropyl betaine and
N
-
(2-dehydroabietyloxy) ethyl-
N
,
N
-dimethyl phosphate betaine (Z01-Z03), which were
synthesised using DAA as starting material (
Scheme 5.25
) [44].
Scheme 5.25
Synthesis of betaine-type amphoteric surfactants (Z01-Z03)
Rosin-based amino acids are widely investigated zwitterionic surfactants. Rosin acid
and dehydroabietylamine can be used as raw materials for the synthesis (
Scheme 5.26
)
of this kind of surfactant (Z04-Z08). Rosin acid chloride can react with an amino
acid to form zwitterionic surfactants. This reaction can take place with different
kind of amino acids to form different kinds of zwitterionic surfactants. Liu and co-
workers reported that abietinylglycine was synthesised by the reaction of glycine
and abietic chloride in a water/acetone system and the reaction was accelerated by
a phase transfer catalyst. Benzyl trimethylammonium bromide was a good catalyst
and pyridine was a good base for the reaction [45]. Fang and co-workers reported
using disproportionated rosin and sarcosine as the main starting materials to prepare
disproportionated rosinoyl sarcosine through a chloride intermediate in the same
way [46, 47].
