Alpha-cleavage

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IUPAC RECOMMENDATIONS 2013

K. K. Murray, R. K. Boyd, M. N. Eberlin, G. J. Langley, L. Li and Y. Naito, Pure Appl. Chem., 2013, 85, 1515-1609, 10.1351/PAC-REC-06-04-06.

Alpha-cleavage
α-cleavage

Homolytic cleavage where the bond fission occurs between the atom adjacent to the atom at the apparent charge site and an atom removed from the apparent charge site by two bonds.

Note: In the case of a distonic ion, it is important to distinguish between fragmentation adjacent to the charge site and fragmentation adjacent to the radical site.
Related Term(s): β-cleavage
Reference(s):

IUPAC. Analytical Division. Compendium of Analytical Nomenclature (the “Orange Book”). Definitive Rules, 1979. Compiled by J. Inczédy, T. Lengyel, A. M. Ure. Blackwell Scientific Publications, Oxford (1997). On-line corrected version: http://www.iupac.org /publications/analytical compendium (2000).

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: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins.

Definitions of Terms Relating to Mass Spectrometry (IUPAC Recommendations 2013); DOI: 10.1351/PAC-REC-06-04-06 © IUPAC 2013.


Index of Terms

 




Orange Book

ORANGE BOOK DEFINITION

IUPAC. Analytical Division. Compendium of Analytical Nomenclature (the “Orange Book”). Definitive Rules, 1979.

Alpha-cleavage

Fission of a bond originating at an atom which is adjacent to the one assumed to bear the charge; the definition of β - cleavage etc follows automatically.

IUPAC Orange Book Chapter 12
Index of Orange Book Terms


Gold Book

GOLD BOOK DEFINITION

IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997).

Alpha-cleavage

(in mass spectrometry) The fission of a bond originating at an atom which is adjacent to one assumed to bear the charge; the definition of ?-, ?-, cleavage then follows automatically. The process:

would thus be described as ?-fission of a ketone with expulsion of a radical R1. . The carbon atoms of the radical R1. are called the ?-, ?-, ?-carbons, starting with the atom nearest the functional group.

Source:

PAC, 1991, 63, 1541 (Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)) on page 1558

(in photochemistry) Homolytic cleavage of a bond connecting an atom or group to an excited chromophore. Often applied to a bond connected to a carbonyl group, in which case it is called a Norrish type I photoreaction.

Note: This reaction should be distinguished from an alpha-(?-)elimination.

Source: PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 302

IUPAC Gold Book
Index of Gold Book Terms