Cyril Norman Hinshelwood – pioneer in physical chemistry worked on Chemical reaction rates, reaction mechanisms.

Cyril Norman Hinshelwood – pioneer in physical chemistry

Article on Cyril Norman Hinshelwood

Biography & contributions

Cyril Norman Hinshelwood, an English physical chemist and Nobel laureate born on June 19, 1897 – October 09, 1967. Norman worked on explosive reaction between hydrogen and oxygen, chemical reaction rates and reaction mechanisms.

In 1956 Norman was awarded with Nobel Prize in chemistry for his work on mechanism of chemical reactions.

While working on the combination of hydrogen and oxygen he described phenomenon of chain reaction.

Norman subsequent work on chemical changes in the bacterial cell proved to be of great importance in later research work on antibiotics and therapeutic agents.

Chain Reactions

A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. Chain reactions are one way in which systems which are in thermodynamic non-equilibrium can release energy or increase entropy in order to reach a state of higher entropy.

In 1913 the German chemist Max Bodenstein first put forth the idea of chemical chain reactions. In 1923, Danish and Dutch scientists Christian Christiansen and Hendrik Anthony Kramers, in an analysis of formation of polymers, pointed out that such a chain reaction need not start with a molecule excited by light, but could also start with two molecules colliding violently in the traditional way.

A chemical chain reaction proceeds by a sequence generally subdivided into three stages

(1) Initiation, in which a reactive intermediate, which may be an atom, an ion, or a neutral molecular fragment, is formed, usually through the action of an agent such as light, heat, or a catalyst.

(2) Propagation, whereby the intermediate reacts with the original reactants, producing stable products and another intermediate, whether of the same or different kind; the new intermediate reacts as before, so a repetitive cycle begins.

(3) Termination, which may be natural, as when all the reactants have been consumed or the containing vessel causes the chain carriers to recombine as fast as they are formed, but more often is induced intentionally by introduction of substances called inhibitors or antioxidants.

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