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MARKUS Rudolph

( Chemist, Nobel Prize in Chemistry 1992)

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Biography MARKUS Rudolph
MARCUS, RUDOLPH (Marcus, Rudolph) (p. 1923) (USA). Nobel Prize in Chemistry 1992.

Born July 21, 1923 in Montreal. He was the only child of a Jewish family. His parents, Marcus and Esther Meir Cohen, had no higher education, knowledge and interest aroused in him by his uncle. Marcus willingly attend school, and at first keen on mathematics, and later, thanks to home chemistry sets - chemistry.

Higher education began to receive in Baron Byng High School, and then continued in Makgillskom University in Montreal. One of his mentors was an expert on the mechanisms of chemical reactions K. Winkler, a disciple of Nobel Laureate S. Hinshelwood.

During his studies he completed several courses specifically mathematics. After receiving his doctorate in 1946 for experimental work on the kinetics of nitration in solution, Marcus joined a new research program at the National Research Council of Canada in Ottawa. The program later became famous, but at the time she only began its existence.

In this council photochemical group headed by E. W. R. STIS, the figure of international scale in the field of free radical reactions. He taught Marcus experimental studies of reaction rates in the gas phase. In 1948, Marcus and his young colleague Walter Trost, organized a seminar to explore the theory of his experimental work. This led him to an extension of postdoctoral fellowships, now in the theoretical field

. Thus, . Marcus purposefully prepared for independent scientific work in theoretical chemistry: mastered the mathematical apparatus, . allowed him to understand the theory, . received the experimental skills in solution and gas phase,
.

In February 1949 he began working at the University of North Carolina at Chapel Hill, a well-known specialist in the field of kinetics of Oscar K. Reiss. Here he formulated a theoretical concept in the transition state, which later became known as the theory of Rice - Ramspregera - Kassel - Marcus (RRKM). The work was published in 1951, and in 1952 he summed up her.

In 1951 went to work in the Brooklyn Polytechnic Institute, where he worked his own program of experimental studies of reaction rates in the gas phase and in solution. His attention was attracted by electrolyte solutions. He wrote the first two articles on this subject in 1954-1955, and in a series of articles published between 1956 and 1965, he investigated the role of solvent molecules in determining the rates of redox reactions in solution

. He gave an explanation of the phenomenon of transfer of one electron, . which there is no new connections and do not break down old, . but there is only a change in the energies and lengths of chemical bonds, . and in the process involved and the solvent molecules, has made the calculation of the energy of such a reorganization in the process of structural change, . caused by single electron transfer,
. He defined the relationship between the driving force (the difference in the energies of reactants and products) of redox reactions and their rate. They found that the relationship between the energy characteristics of the system and its velocity has a parabolic dependence. Rate does not change gradually, and passes through a maximum (region inversion). The more attached a driving force in such processes, the greater their speed first increases and then decreases.

Marcus has identified subtle changes that occur in the structure of a reactant molecules such transformations, and the solvent molecules surrounding them. These changes affect the mobility of electrons, which are known to be the main actors in these reactions. He found that the value of reorganization energy for electron transport depends on the nature of the solvent. The higher the dielectric constant of the solvent, the greater the energy of reorganization. In particular, the water with its high dielectric constant - a bad solvent for the process of rapid electron transfer.

Of the theory of Marcus initially greeted with considerable skepticism, but in the 80's have been confirmed experimentally.

The theory sheds light on the phenomena associated with electron transfer, photosynthesis, cell metabolism, the electrical conductivity of polymers, chemiluminescence and corrosion.

Model Marcus explains the behavior of the electron in the process of photosynthetic reactions. Their ultimate objective - transfer of an electron in a relatively stable state in which he, however, still has enough energy to perform work necessary for the living organism.

The processes of electron transfer are important in living systems. These electron goes from metal ions to organic molecules, and vice versa. Using the theory of Marcus it becomes clear why, for example, iron cations in aqueous medium exchanges electrons slow. By Marcus driving force behind this process is high. To expedite the electronic transfer, the nature of extracted metal cations from water and placed them in a protein shell.

In 1960, completed the experiments in this field, and then spent a half years (1960-1961) at the Mathematical Institute at New York University, listening to the numerous special courses.

In 1964 he joined the University of Illinois at Champaign-Urbain, and no longer engaged in experimental work. In the 1975-1976 academic year was in Europe, . first as a visiting professor at Oxford University, . then, . as laureate Humboldt, . - Technical University of Munich, . where interested in the problem of electron transfer in photosynthesis,
.

In 1978 moved to the California Institute of Technology, where he continues to work.

Marcus received the Nobel Prize in 1992 'for his contribution to the theory of electron transfer reactions in chemical systems. "


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