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The triacylglycerols (TAGs) containing saturated (Sat)‐unsaturated (U) fatty acid moieties (Sat‐U mixed acid TAGs) are widely present in most natural fats and employed in many industrial applications. The mixing behavior of different Sat‐U mixed acid TAGs acts important roles in the physicochemical properties TAG‐based materials. Among the three main mixing states of miscible, eutectic and molecular compound (MC) forming mixtures, fundamental research has been conducted on the MC crystals formed by different Sat‐U mixed acid TAGs to understand the structures, phase behavior and crystallization properties. This article reviews studies to date on the complex thermodynamic, kinetic and structural factors that affect the formation of MC crystals in binary and ternary mixtures of Sat‐U mixed acid TAGs (SatUSat, SatSatU, USatU and UUSat) through specific molecular interactions among the component TAGs. Furthermore, the application of the MC‐forming mixtures containing cacao butter to new types of cocoa butter alternative is reviewed. [ABSTRACT FROM AUTHOR]

We introduce the photoacoustic educational system (PAES), by which we can identify which gas causes the greenhouse effect in a classroom (Kaneko "et al" 2010 "J. Chem. Educ." 87 202-4). PAES is an experimental system in which a pulse of infrared (IR) is absorbed into gas as internal energy, an oscillation of pressure (sound) appears, and then we can measure the absorptance of IR by the strength of sound. In this paper, we construct a simple mathematical model for PAES which is equivalent to the CR circuit. The energy absorption of an IR pulse into gas corresponds to the charge of a condenser and the heat diffusion to the outside corresponds to the energy dissipation by electric resistance. We analyse the experimental results by using this simple model, and check its validity. Although the model is simple, it explains phenomena occurring in PAES and can be a good educational resource. (Contains 4 footnotes and 10 figures.)

An experimental system for detecting infrared absorption using the photoacoustic (PA) effect is described. It is aimed for use at high-school level to illustrate the difference in infrared (IR) absorption among the gases contained in the atmosphere in connection with the greenhouse effect. The experimental system can be built with readily available components and is suitable for small-group experiments. The PA signal from a greenhouse gas (GHG), such as CO[subscript 2], H[subscript 2]O, and CH[subscript 4], can be detected down to a concentration of 0.1%. Since the basic theory of the PA effect in gases due to IR absorption is straightforward, the experiments with this PA system are accessible to students. It can be shown that there is a significant difference in IR absorption between GHGs and the major components of the atmosphere, N[subscript 2], O[subscript 2], and Ar, which helps students understand that the minor components, that is, the GHGs, determine the IR absorptivity of the atmosphere. (Contains 4 figures.)

A study was conducted to analyze a rapid reversible solid-state transition in the A'form of pentadecanoic acid. The acid samples were made using a combination of urea adducts, acid soap and fractional distillation techniques. A stereomicroscope was then utilized to examine single-crystal specimens. Experimental results indicated that the energy barriers among polymorphs supported the conversion transition of B' to A in two steps.

Solid-state phase transitions of pentadecanoic acid were investigated using microscopic observation and micro-Fourier transform infrared spectroscopy. Two martensitic transitions were found in the opposite directions in pentadecanoic acid, between which the starting and resulting polymorphs interchange. The martensitic transitions were induced by a mechanical stress and are dependent on temperature. In addition, the product phases grow in a definite direction and are highly oriented.

The solution-crystallization mechanism was investigated for two polytypes in the M011 modification of n-hexatriacontane (n-C36H74), single-layered structure Mon, and double-layered one Orth II. The crystal growth under controlled supersaturation was followed with a micro- Fourier-transform-infrared spectrometer equipped with an optical system for oblique transmission measurements. Supersaturation dependence of growth behavior was significantly different between Mon and Orth II. Although the Mon crystal continued growing at a supersaturation of 0.27, the overgrowth of Orth II on the (001) face of the Mon crystal was confirmed at supersaturations below 0.21. Such a polytypic transformation was not observed for the Orth II crystal at any supersaturation below 0.30. The growth rate of Mon showed a quadratic dependence on supersaturation, while that of Orth II was approximately linear, suggesting spiral growth and two-dimensional-nucleation mechanisms for Mon and Orth II, respectively. [ABSTRACT FROM AUTHOR]

The solution-crystallization mechanism was investigated for two polytypes in the M011 modification of n-hexatriacontane (n-C36H74), single-layered structure Mon, and double-layered one Orth II. The crystal growth under controlled supersaturation was followed with a micro- Fourier-transform-infrared spectrometer equipped with an optical system for oblique transmission measurements. Supersaturation dependence of growth behavior was significantly different between Mon and Orth II. Although the Mon crystal continued growing at a supersaturation of 0.27, the overgrowth of Orth II on the (001) face of the Mon crystal was confirmed at supersaturations below 0.21. Such a polytypic transformation was not observed for the Orth II crystal at any supersaturation below 0.30. The growth rate of Mon showed a quadratic dependence on supersaturation, while that of Orth II was approximately linear, suggesting spiral growth and two-dimensional-nucleation mechanisms for Mon and Orth II, respectively. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of the two polytypes of n-hexatriacontane (n-C36H74), single-layered structure Mon and double-layered structure Orth II have been investigated by means of solubility measurements and incoherent inelastic neutron scattering. The solubility measurements reveal that Orth II is more stable than Mon by 1.2 kJ/mol because of the advantage of larger entropy. The neutron scattering measurements show that the vibrational modes of Orth II shift to the lower frequencies compared with those of Mon in the frequency region below 120 cm-1. The advantage of Orth II in vibrational entropy due to the low-frequency shifts is estimated to be 9.6 J K-1/mol at 288 K under the harmonic approximation, which nearly agrees with the entropy difference of 6.8 J K-1/mol between Mon and Orth II determined by solubility measurements. These results suggest that the difference in vibrational entropy due to low-frequency modes mainly contributes to the relative thermodynamic stabilities of polytypic structures of long-chain compounds. From the frequency of methyl torsional mode, it is suggested that the cohesive force at the lamellar interface is stronger in Mon than in Orth II. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The molecular displacements on the M011→M101 phase transition of n-hexatriacontane (n-C36H74) have been investigated with an IR microscope designed for the oblique infrared transmission method. It has been clarified that two polytypic structures of the M011 modification, single-layered structure (Mon) and double-layered one (Orth II), both transform to the M101 modification of single-layered structure with their respective mechanisms. On the M011(Mon)→M101 transition, the inclination direction of molecular axis is changed by 90° through an intermediate state in which the molecular chain is set perpendicular to the basal plane of the single crystal. On the other hand, a polymorphic-polytypic composite structural change on the M011(Orth II)→M101 transition is accomplished through two kinds of molecular displacements occurring alternately along the stacking direction of molecular layers. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An experimental system for studying the infrared absorbing properties of greenhouse gases that can be built inexpensively with readily available components is presented. The system is based on an Fourier-transform infrared spectrometer and the activity is suitable for high school students.

The attenuated total reflection (ATR)-FTIR spectroscopic studies of backbone conformation of antifreeze glycoprotein (AFGP) molecules adsorbed at the ice/water interface is presented. The results indicate a clear increase in the [alpha]-helical fraction of AFGP at the ice/water interface in the frozen solution.

Incoherent quasielastic neutron scattering (IQNS) is used for studying the dynamic properties of acyl chains in the three polymorphic phases [alpha], [beta]' and [beta] of tristearin [(C.sub.3][H.sub.5][(OCO[C.sub.17][H.sub.35]).sub.3]]. The studies have shown that the dynamics of acyl chains have depended on their lateral packing and temperature, featuring the characteristics of the [alpha] phase whose acyl chains are most mobile.

The reversible solid-state phase transition between the gamma and alpha phases of oleic acid was followed by 13C solid-state NMR spectroscopy. The factors that have a significant influence on the spectra of cis-monosaturated acyl chains are discussed.