Fall-off from extrapolated values of all chemical reactions at very high temperatures.
At high temperatures the breaking of chemical bonds becomes relatively easy and the slow step in a chemical reaction shifts to the rate at which energy can seep into the bond that is to break. This has been observed by various investigators. A new general theory of reactions is developed here to explain this limiting rate at high temperatures. In the case of cyclopropane and cyclobutane the theory leads to the conclusion that 20 degrees of freedom form a heat reservoir which feeds the energy into the carbon bond that is to break and that this rate becomes controlling above about 1200 degrees K. This would correspond to 20 of the 21 vibrational bonds of cyclopropane feeding energy into the carbon bond that is to break, and there would be no noticeable rise in the number of bonds for cyclobutane. This theory is especially important for shock tubes and detonations, where this falling-off from the extrapolated low temperature rate becomes glaringly obvious.
Eyring
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The University of Utah, Chemistry Department, Salt Lake City, Utah 84112.
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