(394b) Effect of Fatty Acids On Cooling Crystallization of Glycine From Neutral Aqueous Solution

Polymorph control is significant process because different polymorphs induce different properties. In case of crystallization of glycine, it has been well known that α-glycine was crystallized from neutral aqueous solution. In the present work, it was found that γ-glycine could be obtained at neutral aqueous solution/fatty acid interface. γ-Glycine crystal was hanging at the neutral aqueous solution/fatty acid interface with a growth direction along [00-1]. It indicates that the –COOH head groups of fatty acid at the interface influenced the nucleation of γ-glycine because of interaction with NH3+-rich (001) face of γ-glycine. Furthermore, the variation of molecular arrangement of fatty acids with different hydrocarbon length was found to affect significantly the polymorphic selection of glycine. As a result, γ-glycine crystals were obtained from the hexanoic acid and octanoic acid, whereas α-glycine was induced from the fatty acid of which number of carbon is larger than 12 due to extension of molecular surface area at the interface (saturation temperature and cooling rate were 85 ¢ªC and 0.5 ¢ªC/min, respectively).