Reactivity Selectivity Relationships in Reactions of Carbocations with Nucleophiles

Benzhydrylium ions, which have previously been characterized as reference electrophiles in the Mayr group, have been employed for the construction of general nucleophilicity and electrophilicity scales. The kinetics of the reactions of benzhydrylium ions with 15 n-nucleophiles in water and DMSO were measured to yield the N- and s-parameters. Most of the nucleophiles have closely similar slope parameters indicating that the reactions of most n-nucleophiles approximately follow Ritchie's constant selectivity relationship. The different slope parameter for water is recognized as the main reason for deviations from the Ritchie relationship reported in 1986. The rates of the reactions of benzhydrylium ions with solvent mixtures of variable composition have been determined. From plots of the first-order rate constants (log k) versus E of benzydrylium ions, the solvent nucleophilicity parameters are derived. This allow the systematic design of Friedel-Crafts reactions with solvolytically generated carbocations. Rate constants for the reactions of laser flash photolytically generated benzhydrylium ions with chloride and bromide anions have been determined in various solvents and compared with literature data. The rate constants for the ionization of benzhydryl halides and for the reactions of benzhydrylium ions with halide anions and with solvent are combined to give complete free energy profiles for solvolysis reactions. The first SN1 reaction, where ionization and trapping of the carbocation by the solvent could directly be observed, is reported

Self-regulated left-right asymmetric expression of Pitx2c in the developing mouse limb

AbstractThe transcription factor Pitx2c is expressed in primordial visceral organs in a left-right (L-R) asymmetric manner and executes situs-specific morphogenesis. Here we show that Pitx2c is also L-R asymmetrically expressed in the developing mouse limb. Human PITX2c exhibits the same transcriptional activity in the mouse limb. The asymmetric expression of Pitx2c in the limb also exhibits dorsal-ventral and anterior-posterior polarities, being confined to the posterior-dorsal region of the left limb. Left-sided Pitx2c expression in the limb is regulated by Nodal signaling through a Nodal-responsive enhancer. Pitx2c is expressed in lateral plate mesoderm (LPM)–derived cells in the left limb that contribute to various limb connective tissues. The number of Pitx2c+ cells in the left limb was found to be negatively regulated by Pitx2c itself. Although obvious defects were not apparent in the limb of mice lacking asymmetric Pitx2c expression, Pitx2c may regulate functional L-R asymmetry of the limb

Competitiveness of credit associations and credit cooperatives in Japan

This paper investigates how the consolidation process has affected the degree of competition within the segment of Credit Associations (CA) and Credit Cooperatives (CC) in Japan By applying our restricted model we find that Credit Association and Credit Cooperatives operate in monopolistic markets. The results correspond to research findings by Tsutsui and Kamesaka (2005), and Uchida and Tsutsui (2005). Our estimate indicates that size of mutual financial institution has a positive impact on revenue. The same may be seen for the number of branches. In fact, it means that the growth of banks activities is reflected in higher revenues

Research on the mutual financial institutions : comparative study

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