The gas phase reactions of singlet methylene with cyclohexene and cyclopentene over a wide pressure range gave the expected products from C-H insertion and C=C addition; no subsequent decomposition or rearrangement was observed. The product ratios gave intramolecular, per bond, relative insertion rates into the vinylic, allylic, and nonallylic C-H bonds which are the same as for acyclic olefins. Competition reactions with isobutene, however, revealed that the absolute magnitude of these rates is about 50-80% higher than that of the previously studied olefins. The C=C addition rate, on the other hand, is in the same range as that observed for straight chain 1-alkenes. A dynamic effect is proposed to account for the selectivity of both the interand intramolecular effects in C-H insertion.The question of selectivity in the reactions of methylene has been a topic of interest ever since 1956 when Doering et al. reported a study of methylene reactions with liquid hydrocarbons and commented that "Methylene must be classified as the most indiscriminate reagent known in organic chemistry."2 In the work that followed, the importance of phase effects, singlet and triplet methylene reactivity, and methylene precursors were elucidated. In the gas phase, singlet methylene reacts with primary, secondary, and tertiary C-H bonds in the ratio of 1:1.3:1.4. This selectivity is less pronounced in the liquid phase.3 For acyclic alkenes, the insertion rate into vinylic C-H bonds is about 65% as fast as into allylic and paraffinic bonds.3•4 The per bond methylene addition to the C=C bond is about eight to ten times as fast as C-H insertion.Cyclopentene and cyclohexene are ideal systems to measure the selectivity of methylene reactions. They contain three types of C-H bonds as well as the C=C. They are large enough that subsequent reactions of the bicyclic compounds or the methylcycloalkenes formed can be stabilized at easily accessible pressures. Methylene reactions in liquid cyclohexene were studied in Doering's early work2 and later by Kopecky, Hammond, and Leermakers.5 This liquid work showed general agreement with the acyclic alkenes for C-H insertion and a slightly reduced (=¿50%) reactivity at the C=C. Our work represents the first study in the gas phase of cycloalkene systems.6 In order to compare the reactivity of the cyclic and acyclic alkenes, competition studies with isobutene were done as well.
Die Reaktion der Fluoraniline (I) mit Trifluornitrosomethan (II) liefert die Trifluormethylazobenzole (III), dabei entstehen überwiegend die trans‐Isomeren.
Molecules of two related 1,2-amino alcohols are linked via N—H⋯O=S hydrogen bonds, forming chains along [100] for the first compound and along [010] for the second compound.
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