Studies of divalent metal soaps
This thesis contributes towards work whose long term aim is to comprehensively
study organic solutions of metallic soaps.
The thesis begins with an introduction in which the aggregation behaviour
of heavy metal soaps in nonaqueous media is compared and contrasted with
the behaviour of alkali metal soaps in an aqueous medium.
Gravimetry and atomic absorption spectrophotometry are employed to
measure the solubility of the zinc and copper II n-alkanoates in a number
of organic solvents. In most cases the solubility is seen to rise sharply
when a critical solution temperature (eST) is reached.
VPO studies of copper soap solutions indicate the presence of aggregates
of low aggregation number at concentrations close to the concentration
at the eST, and above this concentration the aggregation number increases
over a wide concentration range.
It is concluded that the solutions do not show Krafft behaviour and it
is proposed that formation of a lyotropic liquid crystalline soap phase
is responsible for the eST behaviour.
Up to 4000-fold solubility enhancements of copper II n-alkanoates in
binary hydrocarbon/alcohol solvent systems are observed. Where the
alcohol is of low chainlength, however, a secondary process causes
massive reprecipitation with time; it is proposed that soap/alcohol
complex formation is ultimately responsible.
VPO studies show that copper alkanoates do not aggregate in pyridine;
their high solubility in pyridine is due to complex formation in
solution. A wide survey of complex formation by metal soaps has been
undertaken using the technique of TGA.
TGA shows that alkali and alkaline earth metal soaps can complex with
parent acid. Chromium III n-alkanoates are observed to complex with
parent acid, long chain alcohols and &mines but not esters.
copper 11 soaps are shown to form isolatable pyridine co-ordinate
complexes. The copper 11 dodecanoate dipyridine complex has not been
previously reported. TGA indicates that copper soaps may also complex
with long chain amines.
It is concluded that future solution studies of these metal soap
complexes will prove interesting.