- The Collisionally Induced Dissociation of Allyl and 2-Propenyl Cations
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Pure (1+) and CH3C(1+)=CH2 ions are generated only in metastable fragmentations of 1+., X=Cl, Br, I, and 1+., X=Br, I, respectively.For ion source generated (1+) ions there is some structural interconversion.The structure characteristic feature of their collisional activation mass spectra is the ratio m/z 27 (1+):m/z 26 (1+.).For CH3C(1+)=CH2 the ratio is only weakly dependent upon the translational energy of the ion.For (1+), the ratio rises sharply as translational energy is reduced, from 0.9 at 8 kV to c. 3 at 1 kV. (1+) ions generated by charge reversal of (1-) show higher ratios, resulting from their lower average internal energy content.It must therefore be emphasized that (1+) ion structure assignments should only be made using reference data which apply to specific experimental conditions. (1+) daughter ion structures for a number of well-known fragmentations have been established.The heat of formation of the 2-propenyl cation was measured to be 969+/-5 kJ mol-1.Labelling experiments show that at low internal energies, allyl cations do not undergo atom randomization in c. 1-2 μs; high internal energy ions of longer lifetime (c. 8 μs) show complete atom randomization.H1+ atom loss from +. has been shown to generate (1+) and 13CH2=C(1+)-CH3 without any skeletal rearrangement.
- Burgers, Peter C.,Holmes, John L.,Mommers, Alexander A.,Szulejko, Jan E.
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- SYNTHESIS OF TRIFLUOROMETHYL- AND PENTAFLUOROPHENYLALKENYNES
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A four-stage method was developed for the production of conjugated trifluoromethyl- and pentafluorophenylalkenynes containing a perfluorinated substituent at the triple bond and also the structurally analogous hydrocarbons from the corresponding acetylenic compounds with protection of the triple bond by a dicobalt hexacarbonyl fragment.The method includes the production of trifluoromethyl- and pentafluorophenylalkynyl alcohols and their dicobalt hexacarbonyl complexes, dehydration of the latter, and oxidative demetallation of the obtained complexes of trifluoromethyl- and pentafluorophenylalkenynes by cerium ammonium nitrate.It was shown that trifluoromethylalkenynes can be synthesized by Pd(0)-catalyzed cross coupling of trifluoromethylethynylzinc and 2-iodopropene.
- Bobrovnikov, M. N.,Turbanova, E. S.,Petrov, A. A.
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p. 1445 - 1449
(2007/10/02)
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