Showing papers by "George M. Whitesides published in 1979"
58 citations
TL;DR: In this article, the authors report the development of coupling reactions which permit the facile conversion of (bis(2-diphenylphosphinoeth-yl)amine (l lz's) to a wide variety of water-soluble diphosphines.
Abstract: Sir: The low solubility of common phosphine-transition metal complexes in water has inhibited their application to catalytic transformations in aqueous solutions. Recent experiments have established that complexes derived from Ph2P(m-C6Ha-SO3Na)2 are catalytically active in homogeneous olefin hy-drogenation and hydroformylation reactions in water.3 s Complexes derived from bidentate ligands can have useful differences in chemical stability and catalytic activity from analogous complexes containing only monodentate ligands.6 Here we report the development of coupling reactions which permit the facile conversion of (bis(2-diphenylphosphinoeth-yl)amine (l lz's to a wide variety of water-soluble diphosphines
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TL;DR: In this article, the influence of molecular symmetry on reaction rates is examined with an approach in which reactions are viewed as electronic transitions between states of reacants and products (described, in turn by quasiadiabatic potential surface).
Abstract: The influence of molecular symmetry on reaction rates is examined with an approach in which reactions are viewed as electronic transitions between states of reacants and products (described, in turn by quasiadiabatic potential surface). The moleculer Hamiltonian is used to derive selection rules for these transitions. The complete Hamilatonian has no useful symmetery. Neglect of non-Born-Oppenheimer and spin-orbit terms (and of other angular momentum coupling terms) leads to an apporixmate Hamiltonian and to selection rules which from the basis of the Woodward-Hoffmann rules. This apporch provides an alternative to the adiabatic potantial surfaces, reaction coordinates, and transition state theory used in more familiar discussions of the Woodward-Hoffmann rules. Further, it provides a particulary clear method for discussing violations of these symmetry rules, and for differentiating concerted and nonconcerted reactions.
34 citations
TL;DR: To facilitate separation of these enzyme-containing gels from suspension, a ferrofluid — a surfactant-stabilized magnetite colloid — has been entrapped in them and suggests that acylation and polyacrylamide gel formation are concurrent in the experiment procedures used.
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TL;DR: Experimental procedures that allow cross-linked polyacrylamide gels to be formed by free-radical polymerization in solutions containing adenylate kinase with preservation of 50 – 90% of the activity of the enzyme are designed.
8 citations
TL;DR: In this article, a Molekulsymmetrie auf die Reaktionsgeschwindigkeit wird mit einem Verfahren untersucht, das chemische Reaktionen als elektronische Ubergange zwischen Edukt- und Produktzustanden betrachtet, wobei diese Zustande durch quasiadiabatische Potentialflachen beschrieben werden.
Abstract: Der Einflus der Molekulsymmetrie auf die Reaktionsgeschwindigkeit wird mit einem Verfahren untersucht, das chemische Reaktionen als elektronische Ubergange zwischen Edukt- und Produktzustanden betrachtet, wobei diese Zustande durch quasiadiabatische Potentialflachen beschrieben werden. Fur diese Ubergange werden unter Verwendung des molekularen Hamilton-Operators Auswahlregeln hergeleitet. Der vollstandige Hamilton-Operator weist keine brauchbare Symmetrie auf; die Vernachlassigung von Nicht-Born-Oppenheimer-Termen, von Spin-Bahn-Kopplungstermen und anderen Drehimpulskopplungstermen ergibt einen approximierten Hamilton-Operator und fuhrt zu Auswahlregeln, welche die Basis der Woodward-Hoffmann-Regeln bilden. Dieser Ansatz bietet eine Alternative zu den adiabatischen Potentialflachen, den Reaktionskoordinaten und der Theorie des Ubergangszustandes, die bei der Diskussion der Woodward-Hoffmann-Regeln ublicherweise zugrunde gelegt werden. Daruber hinaus lassen sich mit diesem Ansatz Verletzungen der Symmetrieregeln besonders gut diskutieren und konzertierte von nichtkonzentrierten Reaktionen unterscheiden.