 |
Geoffrey's Project Page - RISE Summer 2006 |
 |
Intern: Geoffrey Leonard, Chemical Engineering,
University of Virginia
Mentor: Ryan Snyder
Faculty Supervisor: Michael Doherty
Department: Chemical Engineering |
AN INVESTIGATION INTO THE SOLUBILITY, ENTHALPIC, AND METASTABLE ZONE WIDTH, ALTERNATIONS FOR _,_-ALKANEDICARBOXYLIC ACIDS
In many molecular systems with carbon chains, physical properties alternate,
namely the melting point, density, solubility, and enthalpies of solution, based
upon whether the molecule has an even or odd number of carbon atoms. For the
_,_-Alkanedicarboxylic acid series, the even numbered species have
characteristically greater melting points and densities; this alternation
results from a consonance between torsional straining and non-ideal packing
effects when the odd numbered species crystallise. The objective of this study
was to investigation whether alternation developed in the phase transition
properties of solubilities (in water and in amphiphilic solvents), enthalpies
of solution, and meta-stable zone widths. The solvophobic effects of water
produced the lowest solubilities, and the solvent molecules capable of multi-
faceted H-bonding yielded the greatest solubilities. In all solvents the
solubilities displayed two dominant trends: the odd acids solvated more readily
and both the even and odd acids’ solubilities monatomically decreased as the
chain length increased. Enthalpies of solutions were determined from the
solubility data, and this property too displayed an alternative trend that
reconciled with known enthalpies of fusion. Metastable zone width measurements
(using the polythermal method) characterised the thermodynamic driving force
for nucleation, the _-factor, and across the series, the _-values increased and
displayed an alternation – odd species had systematically lower values.
Return to the RISE 2006 project list
