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Several amino acids were tested to catalyze the transition-metal-free direct C-H arylation of unactivated benzene derivatives. Among them, proline was found to be an excellent catalyst for the cross-coupling between aryl halides and unactivated arenes. The reaction presumably involves an aryl radical anion as the intermediate based on several experiments. The reaction using this catalyst system offers an option toward establishing an environmentally benign and cost-effective route to biaryls.

SummarySurface and micellar properties of a homologous series of Octaethylene glycol-n-alkyl ethers (C,~Es; n = 9 to 15) have been studied in aqueous solutions by the surface tension measurements. The effects of the alkyl chain length comprising even and carbon numbers have been examined in order to evaluate the surface free energy A G A_ w and the standard free energy AG~ for the micellization obtained from their surface tension data. The areas per molecule and the equilibrium surface tension values at the CMC decreased with an increasing carbon number and they showed zigzag curves by the difference in even and odd carbon numbers.These findings may be attributed to the differences in the molecular orientation between the molecules with even carbon number and ones with odd carbon number on the air-water interface at CMC. A GA_w values decreased linearly with an increasing alkyl chain length but did not show a zigzag line by the differences in even and odd carbon numbers. This suggests that the molecular orientation is not influenced by the difference between their even and odd carbon numbers in the alkyl chain on the surface of the very diluted solution, and their molecules form some stable adsorbed films with an increase of the alkyl chain length. A division of A GA_ w into the contribution made both by the hydrophilic group AG~_w (-W) and by the hydrophobic group A GA-w ( -CH2 -) was attempted as follows; A GA-w (-CH2-) = -0.80 kcal/mol and AGa_w(-W) = + 0A5 kcat/mol. The free energy changes AG m of micellization were discussed on the basis of the CMC data obtained from the surface tension measurements by treating the formation of micelles as analogous to phase separation, and the contribution from the each moieties in the molecule were calculated as follows; AG m (-CH2-) =-0.68 kcal/mol and AGm(-W) = + 1.54 kcal/mol. The difference between AG~_w and AG,~ is discussed using their data. Key wordsNonionic surfactants with even and odd carton atoms, contribution of two moieties.

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The micellar properties of aqueous binary mixed solutions of sodium glycocholate, NaGC, and octa-oxyethylene glycol mono-n-decyl ether, C10Es, have been studied on the basis of surface tensions, the mean aggregation number and the polarity of the interior of the micelles. The mean aggregation number, measured by steady state quenching method, decreased with the increase of the mole fraction of NaGC in the mixed system. The polarity of the interior, estimated by the ratio of first and third vibronic peak in a monomeric pyrene fluorescence emission spectrum, suggested that the hydrophobicity ofintramicelles increased with the increase of the mole fraction of NaGCin the mixed system. These are considered to be caused by the differences in the chemical structure and the hydrophobic nature between NaGC and C10Es. The mean aggregation number and the polarity of the interior for each micelle near the CMC in lower total concentration of surfactants showed the tendency approaching those of pure micelle of the nonionic surfactant. This suggests that the ratio of NaGC in the initial micelles in the range of lower total concentration near the CMC is lower than that of the corresponding prepared mole fraction in the mixed system. This lower value was confirmed also from theoretical calculation of the ratio of NaGC at the CMC in the mixed micelle by regular solution treatment of Rubingh in the solution.