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| Odd-even alternations in thermodynamic properties (melting point, solubility enthalpy, sublimation, etc.) are well-known in the alkyl derivatives. But few attentions are focused on kinetics, which is essential for the design of manufacture process. In this work, the nucleation kinetics of a series of dicarboxylic acids (HOOC-(CH2) n-2-COOH, n=4-12) in ethanol were determined based on induction time measurement at constant supersaturations. The results revealed that the odd-even alternation existed in kinetics as well: odd acids (n=odd) exhibited quicker nucleations compared to the even ones (n=even). We attempted to give insight into the odd-even alternation machenism of nucleation kinetics. Detailed investigations were carried out on molecular arrangements and intermolecular interactions. The energies of intramolecular torsions and intermolecular interacitons were calculated using Materials studio (Accelrys Software Inc.). Relatively higher torsional energy barriers in odd acids crystals and larger interaction energies between odd diacids and ethanol molecules were observed and believed to cause slower nuclei formation of odd acids during solution crystallization compared to even ones. Furthermore, nucleation kinetics is definitely useful for the development of crystallization processes for dicarboxylic acids.this paper. |
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| Keywords:crystallization; nucleation kinetics; dicarboxylic acid; odd-even effect; induction time |
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