physical chemistry Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mecha ...

, the McConnell equation gives the probability of an unpaired electron in an in aromatic radical compound (such as

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

C_6H_6^-

) being on a particular atom. It relates this probability, known as the "spin density", to its proportional dependence on the hyperfine splitting constant. The equation is

a = Q \rho,

where

a

is the hyperfine splitting constant,

\rho

is the spin density, and

Q

is an empirical constant that can range from 2.0 to 2.5 mT.

History

The equation is named after

Harden M. McConnell Harden M. McConnell (July 18, 1927 – October 8, 2014) was an American physical chemist. His many awards included the National Medal of Science and the Wolf Prize, and he was elected to the National Academy of Science." Education and career Hard ...

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider ...

, who first presented it in 1956.

References

* {{cite book , last1 = Atkins , first1 = Peter , authorlink1 = Peter Atkins , last2 = de Paula , first2 = Julio , title = ''Atkins' Physical Chemistry'' , edition = 9th , publisher = Oxford University Press Chemical physics