Perrin mechanism

For a complete static quenching following the Perrin mechanism, Eq. (19.9) is derived, where r0 (nm) is the electron transfer distance between donor and acceptor molecules (molecular center to center). 

Nemst, for example, argued that physics forms the theoretical basis of all sciences, including chemistry. 18 A statement by Emile Dubois-Reymond to the effect that there was a need for a physical chemistry to create a "mathematical mechanics of knowledge" and a "complete picture of molecular processes" 19 was used to preface the first issue of the Zeitschrift fur physikalische Chemie. For van t Hoff, this was to be achieved through "the application of physical expedients, methods, and instruments to chemical problems" in establishing "comprehensive principles."20 Less concretely, Jean Perrin wrote that "really, there is no particular method proper to chemical physics [but] rather a physicochemical esprit."21 Perrin s successors at the Universite de Paris understood this remark to mean that physical chemistry at the turn of the century was "whatever interested Jean Perrin, just as physical chemistry at Berkeley was whatever interested Gilbert N. Lewis. "22... 

Among French physical chemists, Perrin and his immediate circle of colleagues were unique in interesting themselves in kinetics and activation mechanisms. The other best-known practitioners of physical chemistry in France, Henry LeChatelier and Pierre Duhem, concentrated on studies of chemical equilibria and thermodynamic potential. 

At the Faraday meeting, Langmuir had emphasized the necessity for chemists to explain phenomena in terms of quantum relationships, insisting "A molecule cannot dissociate by a continuous process.. . . We ought to consider these phenomena frankly as quantum phenomena." For Langmuir, it made no sense to talk of a series of frequencies "It is very difficult to get a physical conception of a mechanism which involves the product of several intensities."93 To this, Perrin replied that he meant that the reaction takes place in "steps" in response to different radiation frequencies. 94 Langmuir remained unconvinced in 1929, when he wrote in an article, "Modern Concepts in Physics and Their Relation to Chemistry,"... 

A good deal of this work had no impact in the development of models of molecular structure and the elucidation of reaction mechanisms one reason was Perrin s own coolness to quantum wave mechanics. 108 Another, according to Oxford s Harold Thompson, who studied with Nernst and Fritz Haber, was that researchers like Lecomte "did not know enough chemistry he was a physicist." 109 Perrin, too, approached physical chemistry as a physicist, not as a chemist. He had little real interest or knowledge of organic chemistry. But what made his radiation hypothesis attractive to many chemists was his concern with transition states and the search for a scheme of pathways defining chemical kinetics. 

See C. K. Ingold, I. Dostrovsky, and E. D. Hughes, "Mechanisms of Substitution," JCS 149 (1946) 173194 and esp. Ingold, "Les reactions de la chimie organique (quatre conferences), Actualites Scientifiques et Industrielles, no. 1037 (Paris Hermann, 1948), 3238. These lectures were given at the Faculty of Sciences in Paris in May 1946 on the invitation of Edmond Bauer, Jean Perrin s successor at the Sorbonne and the Laboratoire de Chimie Physique. 

Participants in the second conference (April 1925) of the Institut International de Chimie Solvay in Brussels. The topic was "Structure and Activity," and four papers were devoted to activation or mechanism in chemical reactions. Henry Armstrong and Jean Perrin are seated at the center section of the adjoining tables. Andre Job and Thomas Martin Lowry are to Perrin s left. Courtesy of the Instituts Intemationaux de Physique et Chimie (Solvay), Brussels. 

F. Perrin Quantum mechanical theory of long-range energy transfer between atoms... 

The only apparently viable alternative mechanism to explain the observed unimolecular behavior is one that was originally proposed in 1919 by Perrin and became known as the radiation hypothesis. In the absence of any significant body of kinetic data, Perrin proposed that reactant molecules obtain the energy required... 

Jean Perrin (1870-1942) pursued the nature of atoms his whole career (8). When the eyes of quantum mechanics were just developing in the 20 century, Perrin reasoned that the missing rotational heat capacity was due to a very small moment of inertia for atoms. This could only occur if the mass was concentrated in a very small volume. He saw atoms as spherical, but not as uniformly distributed masses. But, if most of the mass was concentrated in a veiy small volume, what determined the colhsion diameter measured from the gas viscosity ... 

Perrin,78 and subsequently Eberson79 and Kochi80 81 and others82-85 carried out extensive studies to probe this mechanism and its scope. Whereas its importance... 

The reason for our reservation in the definition of unimolecular reactions is now clear. Lindemann s mechanism would account for the independence over large ranges— and this corresponds to our experimental criterion of unimolecularity. Perrin seeks to extrapolate the experimental observations to infinite dilution, which may not be permissible. 

B. Perrin, Dust Generation from a Heated Bulk Solid, BE Honours Thesis, Mechanical Engineering, University of Wollongong, 1999. 

The cleavage of the C-halogen bond has been most extensively studied. A fair amount of experiments have been designed to elucidate the reaction mechanism. For details the reader is referred to reviews by Elving 470 Elving and Pullmann Perrin 15 and Brown and Harrison 12K... 

In such a case, no conclusion about the mechanisms can be reached from the form of 4(t) and the observed rate will be determined primarily by the fastest process. By extension of the argument, one easily sees that marked deviation of any of the parallel processes from exponential decay will be reflected in the overall rate with possible change in the functional form. Thus, if the rotation is described by exp(-2D t) as in Debye-Perrin theory, and the ion displacements by a non-exponential V(t), one finds from eq 5 that 4(t) = exp(-2D t)V(t) and the frequency response function c(iw) = L4(t) = (iai + 2D ) where iKiw) = LV(t). This kind of argument can be developed further, but suffices to show the difficulties in unambiguous interpretation of observed relaxation processes. Unfortunately, our present knowledge of counterion mobilities and our ability to assess cooperative aspects of their motion are both too meagre to permit any very definitive conclusions for DNA and polypeptides. 

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