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Reaction of acetylenic gama-glycols. XXXVII. Dehydroxylation and decarbonylation processes in MS-spectra of sym. aromatic diols without and with halogen substituents in para position of phenyl

Jasiobędzki W., Olejnik M.

Bulletin of the Polish Academy of Sciences. Chemistry

2002

Vol. 50, No. 3

323-334

The electron ionization-induced fragmentation patterns of five diols (with H, F, Cl, Br, I substituents in para positions of phenyls) have been studied, especially the title processes. Alternation of dehydroxylation and decarbonylation processes has been found. The elimination of CO causes a rearrangement of the neighbouring aryl and H. The formation of cumulene ions is possible from M(+*)-H(2)O and M(+*)-H(2)O, X* ions. It has been shown that the acetylenic bond has the ability to hold Ph*", PhX* (X=halogen), CeH4, H. The halogen (type), in comparison with the unsubstituted diol, introduces quantitative and not qualitative changes. With a decrease in the induction effect of the halogen, the relative intensity (%) of fragment ions increases, especially of those having small m/z values.

(13)C kinetic isotope effects in the decarboxylation of phenylpropiolic acid (PPA) assisted with formic acid and (13)C KIE in the decarbonylation of formic acid in the presence of PPA

Zieliński M., Zielińska A., Paul H., Papiernik-Zielińska H.

Polish Journal of Chemistry

1998

Vol. 72, nr 12

2551-2555

Carbon-13 kinetic isotope effects, (13)C-KIE, in the decarboxylation of phenylpropiolic acid (carboxyl C-13) in formic acid medium and (13)C KIE in the decarbonylation of liquid formic acid assisted with PPA and acetophenone have been studied in the 70-100 degree C temperature interval. The kinetic and isotope results have been discussed and interpreted as indicating that the formation of C alpha-H bond, preceded by the protonation of acetylenic bond of PPA, is the rate determining step followed by carbon dioxide splitting. The (13)CO-KIE in the carbon monoxide generation assisted with PPA is much larger than the (13)CO-KIE observed in the generation of CO in the presence of phenylacetylene. Thus the decaeboxylation of PPA and decarbonylation of formic acid are interrelated processes proceeding in the reaction cage.