モノグリセリドの多形 (第4報) : 分子鎖長と熱力学量について

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With a total of 10 kinds of synthesized 1-monoglycerides, seven of even-numbered monoglycerides of C10 to C22 (Carbon numbers of fatty acid) and odd-numbered monoglycerides of C15 C17 and C19, examinations were made on the presence of Sub- α2, and their correlation to modification numbers, transition temperature, enthalpy and entropy by difference in length of the molecular chain and even-odd number of carbons. 1) Sub- α2 was observed not only in C18, C20 and C22, but also in C19, but not in those below C17. Comparison of the IR spectrum of Sub- α2 with that of Sub- α1 showed that they are quite similar with the exception of a slight difference in the OH absorption band. Transition from Sub- α2 to Sub- α1 is reversible. 2) Transition temperature (below 310 K, 37°C) of monoglycerides with a short chain of below C15 showed a difference from the values reported in literature when in metastable state (α, Sub α1). Regarding its correlation to the number of carbons, transition temperature of α→ fusion and α → fusion increased β → regulary with increase in the number of carbons, and there was no alternation between even and odd number of carbons. However, such alternation was seen in the transition of Sub- α1 to α and of Sub- α2 to to Sub- α1, and this phenomenon was entirely reverse of that in triglycerides. 3) With respect to the correlation of enthalpy and entropy to the number of carbons, enthalpy and entropy of α → fusion and Sub- α1→α of manoglycerides with above C17 chain showed the same tendency as the transition temperature. Alternation appeared in the case of β→ fusion, differing from the transition temperature. This may be due to the difference in the optically active L and DL compounds of monoglycerides. In the transition of Sub-α to α in monoglycerides of less than C16, transition enthalpy increased in inverse proportion to the decrease in the number of carbons. This may be due to the occurrence of a competitive action between the fatty acid group and glycerol group at the time of transition, resulting in the increasing action of the glycerol group with shortening of the molecular chain and in a metastable state. The enthalpy and entropy per methylene group were R/2 and Rln 3, respectively, agreeing well with theoretical values.

モノグリセリドの多形 (第4報) : 分子鎖長と熱力学量について

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