2922-51-2Relevant articles and documents
Surface and interlayer base-characters in lepidocrocite titanate: The adsorption and intercalation of fatty acid
Maluangnont, Tosapol,Arsa, Pornanan,Limsakul, Kanokporn,Juntarachairot, Songsit,Sangsan, Saithong,Gotoh, Kazuma,Sooknoi, Tawan
, p. 175 - 181 (2016/03/30)
While layered double hydroxides (LDHs) with positively-charged sheets are well known as basic materials, layered metal oxides having negatively-charged sheets are not generally recognized so. In this article, the surface and interlayer base-characters of O2- sites in layered metal oxides have been demonstrated, taking lepidocrocite titanate K0.8Zn0.4Ti1.6O4 as an example. The low basicity (0.04 mmol CO2/g) and low desorption temperature (50-300 °C) shown by CO2- TPD suggests that O2- sites at the external surfaces is weakly basic, while those at the interlayer space are mostly inaccessible to CO2. The liquid-phase adsorption study, however, revealed the uptake as much as 37% by mass of the bulky palmitic acid (C16 acid). The accompanying expansion of the interlayer space by ~0.1 nm was detected by PXRD and TEM. In an opposite manner to the external surfaces, the interlayer O2- sites can deprotonate palmitic acid, forming the salt (i.e., potassium palmitate) occluded between the sheets. Two types of basic sites are proposed based on ultrafast 1H MAS NMR and FTIR results. The interlayer basic sites in lepidocrocite titanate leads to an application of this material as a selective and stable two-dimensional (2D) basic catalyst, as demonstrated by the ketonization of palmitic acid into palmitone (C31 ketone). Tuning of the catalytic activity by varying the type of metal (Zn, Mg, and Li) substituting at TiIV sites was also illustrated.
Investigation of the modes of solubilization and norrish II photoreactivity of 2- and sym-n-alkanones in the solid phases of n-heneicosane and two homologues
Nu?ez, Alberto,Hammond, George S.,Weiss, Richard G.
, p. 10258 - 10271 (2007/10/02)
The nature of the solubilization sites and the solubility limits of a homologous series of 2- and sym-n-alkanones (2-N and m-N, respectively) have been investigated in the hexagonally and orthorhombically packed layered solid phases of heneicosane (C21) by differential scanning calorimetry, deuterium magnetic resonance, and optical microscopy. The photoselectivity and relative quantum efficiencies of product formation from the alkanones in the same solid phases were determined. Results from experiments employing the solid phases of eicosane (C20) and hexacosane (C26) were also obtained. The data show that the solid phases of n-alkanes impose severe restrictions on the motions of the alkanones and their photochemically-generated hydroxy-1,4-biradical intermediates only when the solutes fit well within a solvent layer. In those cases, extremely large photoselectivities, larger than those from analogous smectic liquid-crystalline phases, can be achieved. However, the ability of a solid n-alkane phase to incorporate an alkanone of a different length is much more limited than in the smectic phases. Eutectic mixtures and phase-separated alkanone crystals are obtained in many of the systems investigated.
Asymmetric Reduction of Aliphatic Short- to Long-Chain β-Keto Acids by Use of Fermenting Bakers' Yeast
Utaka, Masanori,Watabu, Hisashi,Higashi, Hiroshi,Sakai, Takashi,Tsuboi, Sadao,Torii, Sigeru
, p. 3917 - 3921 (2007/10/02)
Eleven β-keto acids, ranging from 3-oxobutanoic to 3-oxooctanoic acids, were reduced with fermenting bakers' yeast to the corresponding optically active β-hydroxy acids, which were isolated as the methyl esters.In all cases, the (R)-hydroxy acids were obtained in >/=98percent ee, except for 3-oxobutanoic acid, which afforded the (S)-hydroxy acid in 86percent ee.Inhibition of fermentation was observed for 3-oxoundecanoic to 3-oxotetradecanoic acids, leading to no reduction.Lowering of the substrate concentration was found to be appreciably effective in avoiding inhibition.
LIQUID-CRYSTALLINE SOLVENTS AS MECHANISTIC PROBES. 23. NORRISH II REACTIONS OF 2- AND SYM-ALKANONES IN THE ISOTROPIC, SMECTIC B, AND CRYSTALLINE PHASES OF n-BUTYL STEARATE.
Treanor, Richard L.,Weiss, Richard G.
, p. 1371 - 1392 (2007/10/02)
n-Alkanones with the carbonyl group at the 2 or central positions (1 and 2, respectively) have been irradiated in the isotropic, smectic B, and two solid phases of n-butyl stearate (BS).The lengths of the ketones were varied from 11 to 31 carbons.The ratios of elimination/cyclization products and diastereomeric cyclobutanol products were measured for each as a function of temperature and BS phase.The effect of 1 and 2 on the phase transition temperatures of BS has been correlated with changes in the product ratios.The experiments demonstrate that a very sensitive cooperative relationship exists between the ease with which 1 and 2 fit into the ordered phases of BS and the degree to which the solvent matrices influence ketone photochemistry.The influence of solvent order on the product ratios is distinctly different for 1 and 2, and for the two product ratios from one ketone.
