IUPAC > Gold Book > alphabetical index > A > α-cleavage (alpha-cleavage)
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α-cleavage (alpha-cleavage)
  1. (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 β-, γ-, cleavage then follows automatically. The process:
    A00004
    would thus be described as α-fission of a ketone with expulsion of a radical R1. . The carbon atoms of the radical R1. are called the α-, β-, γ-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
  2. (in photochemistry) Homolytic cleavage of a bond connecting an atom or group to a specified group. Often applied to a bond connected to a carbonyl group, in which case it is called a Norrish type I photoreaction. This reaction should be distinguished from an alpha- (α-)expulsion.
    Source:
    PAC, 1996, 68, 2223 (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2228
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Cite as: IUPAC Compendium of Chemical Terminology, Electronic version, http://goldbook.iupac.org/A00004.html.
Transformed and rewritten from PDF version (entry http://www.iupac.org/goldbook/A00004.pdf)
by: Miloslav Nic, Jiri Jirat, Bedrich Kosata, ICT Prague, Czech Republic
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