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Unsaturated ketenes: A study of their formation and rearrangement by tandem mass spectrometry and low‐temperature infrared spectroscopy
Author(s) -
Maquestiau André,
Pauwels Pascal,
Flammang Robert,
Lorenčak Primož,
Wentrup Curt
Publication year - 1986
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210210505
Subject(s) - meldrum's acid , chemistry , ketene , isomerization , mass spectrometry , allene , infrared spectroscopy , pyrolysis , methylene , vinyl chloride , photochemistry , mass spectrum , tandem mass spectrometry , organic chemistry , ion , catalysis , polymer , chromatography , copolymer
A combination of collisional activation mass spectrometry and low‐temperature infrared spectroscopy has been used to monitor the production and isomerization of vinyl‐ and methylene‐ketenes. Vinyl‐ and 2‐propenyl‐ketenes were produced by flash vacuum pyrolysis of β,γ‐unsaturated acid chlorides. Vinyl(carboxyl)ketenes, vinylketenes and methyleneketenes were obtained from Meldrum's acid derivatives (5‐alkylidene‐1,3‐dioxane‐4,6‐diones). The formation of methyleneketenes by pyrolysis of α, β‐unsaturated acid chlorides is only indicated in the mass spectrometry experiments. Carbonylcyclopropane was obtained by pyrolysis of cyclopropylcarbonyl chloride or the corresponding Meldrum's acid derivative. The methyleneketenes isomerize to vinylketenes in the gas phase, particularly under conditions involving long contact times. Carbonylcyclopropane thermally decarbonylates to allene, not methylacetylene. Molecular ions of vinylketenes are obtained via pyrolysis of either acid chlorides or Meldrum's acid derivatives. Molecular ions of alkylmethyleneketenes are obtained pure only by electron impact induced fragmentation of Meldrum's acid derivatives.