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ion pair return

Also contains definitions of: external ion-pair return, hidden return, internal return

The recombination of a pair of ions R+ and Z formed from ionization of RZ. If the ions are paired as a tight ion pair and recombine without prior separation into a loose ion pair this is called 'internal ion-pair return':
It is a special case of 'primary geminate recombination'. If the ions are paired as a loose ion pair and form the covalent chemical species via a tight ion pair, this is called 'external ion-pair return':
It is a special case of 'secondary geminate recombination'. When the covalent molecule RZ is reformed without direct evidence of prior partial racemization or without other direct evidence of prior formation of a tight ion pair, (e.g. without partial racemization if the group R is suitably chiral) the internal ion-pair return is sometimes called a 'hidden return'. External (unimolecular) ion-pair return is to be distinguished from 'external (bimolecular) ion return', the (reversible) process whereby dissociated ions are converted into loose ion pairs:
PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1127
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IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
Last update: 2014-02-24; version: 2.3.3.
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