On the entropy of fusion

The asymptotic value of the melting entropy, i.e. ΔS_f = R ln 2 for vanishing relative change of volume on melting, can be derived from the vibrational entropy due to vibrating dislocations, which are introduced into a material on melting.     

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as factor Xa inhibitor

Intravascular clot formation is an important factor in a number of cardiovascular diseases. Therefore, the prevention of blood coagulation has become a major target for new therapeutic agents. One attractive approach is the inhibition of factor Xa (FXa), which is a key enzyme in coagulation cascade responsible for the generation of thrombin by limited proteolysis of its zymogen, prothrombin. We have investigated 1-arylsulfonyl-3-piperazinone derivatives, containing a 4-(piperidino)pyridine group in place of guanidino and/or amidino groups, and discovered compound M55113 (30a: 4-[(6-Chloro-2-naphthalenyl)sulfonyl]-1-[[1-(4-pyridinyl)-4-piperidinyl]methyl]piperazinone), as a potent inhibitor of FXa (IC50=0.06 microM) with high selectivity for FXa over trypsin and thrombin.     

Solvent free synthesis of polyaniline-clay nanocomposites from mechanochemically intercalated anilinium fluoride

Nanocomposites consisting of conducting polyaniline and clay minerals were successfully synthesized from mechanochemically intercalated anilinium fluoride; the nanocomposites prepared by the mechanochemical intercalation method contained much more polyaniline in the clay layers than those prepared by a conventional solution method.     

Effect of 1,10-phenanthroline on the extraction and separation of lithium(I), sodium(I) and potassium(I) with thenoyltrifluoroacetone

The extraction of Li⁺ with thenoyltrifluoroacetone (Htta) in the presence of 1,10-phenanthroline (phen) has been studied in various organic solvents. The remarkable enhancement of the extraction of Li⁺, that is a synergistic effect, was observed by the addition of phen, and the high extractability of Li⁺ was attained in toluene, benzene, chlorobenzene and o-dichlorobenzene. The extraction equilibrium of Li⁺, Na⁺ and K⁺ (denoted as M⁺) in the presence or absence of phen in chlorobenzene and the adduct formation reaction in the organic phase were studied in detail. The adduct of Li⁺ was Li(tta)(phen) in the wide concentration range of phen in the organic phase, while in Na⁺ and K⁺ M(tta)(phen)₂ also exists in the high concentration region. The maximum value of the separation factor between Li⁺ and Na⁺ was observed in the present system and was larger than that in the Htta-trioctylphosphine oxide (TOPO)-benzene system reported previously.     

Extraction equilibrium of palladium(II) with 2-methyl-8-quinolinol into supercritical carbon dioxide fluid

The present study is concerned with the extraction behavior and equilibrium of Pd(II) with 2-methyl-8-quinolinol (HMQ) into supercritical fluid CO(2) (SF-CO(2)). Pd(II)-HMQ complex extracted from a weakly acidic solution (pH 2-3) into SF-CO(2) was determined to be Pd(MQ)(2) on the basis of a slope analysis. The extraction constant K(ex,SF) (=[Pd(MQ)(2)](SF)[H(+)](2)[Cl(-)](4)[PdCl(4)(2-)](-1)[HMQ](-2)) was determined to be 10(4.3+/-0.2) at 8.5 MPa, 45 degrees C and I=0.4 M (H,Na)Cl (1 M=1 mol dm(-3)). The distribution behavior of HMQ between an aqueous and a SF-CO(2) phase was examined so as to discuss quantitatively the extraction equilibrium. The extraction constant (K(ex,Cy)) of Pd(II) with HMQ into cyclohexane with a similar polarity to SF-CO(2) was determined and the K(ex,SF) was compared with the K(ex,Cy). Pd(II) at the concentration range of 10(-5)-10(-4) M in the aqueous solution (pH<3) containing relatively high concentration of chloride ion was found to be extracted efficiently by the SF-CO(2) extraction.