627-21-4Relevant articles and documents
Removal of water - a factor influencing the synthesis of alkynes in a phase-transfer catalyzed β-elimination reaction
Zakrzewski,Huras,Sas,Zelechowski,Bombinska
, p. 1051 - 1057 (2008/09/21)
Acetylene derivatives 4 were synthesized from the corresponding vicinal bromo compounds 2 in the phase-transfer catalyzed hydrogen bromide β-elimination reaction using solid potassium hydroxide as a base, xylene as a solvent, and a phase-transfer catalyst. The yields of the synthesized acetylene derivatives 4 were substantially improved when water formed in the process had been removed.
Gas-phase kinetic and mechanistic studies of some interconverting alkylcyclopropene pairs: Involvement of dialkylvinylidene intermediates and their quantitative behaviour
Graf Von Der Schulenburg, Wilhelm,Hopf, Henning,Walsh, Robin
, p. 1963 - 1979 (2007/10/03)
The pyrolyses of two isomeric pairs of alkylcyclopropenes, namely 1,3-dimethyl- (15) and 1-ethyl-cyclopropene (16), and 1,3,3-trimethyl- (5) and 1-isopropyl-cyclopropene (17), have been studied in the gas phase. Complete product analyses at various conversions up to 95% were obtained for the decomposition of each compound at five temperatures over a 40°C range. The time-evolution data showed that the isomerisation reactions 15?16 and 5?17 were occurring. Kinetic modelling of each system allowed the determination of rate constants for these and all other decomposition processes. Tests confirmed that all reactions were unimolecular and homogeneous. Arrhenius parameters are reported for overall reactions and individual product pathways. Further kinetic analysis allowed us to extract the propensities (at 500 K) for 1,3-C-H insertion of the dialkylvinylidene intermediates involved in the rearrangements as follows: kprim:ksec: ktert = 1:16.5:46.4. Additional experiments with 13C-labelled cyclopropenes yielded alkyl group migration aptitudes for the dialkylvinylidenes (from the pattern of 13C in the alkyne products) as follows: Me:Et:iPr=1:3.1:1.5. Explanations for these trends are given. Another important finding is that of the dramatic rate enhancements for 1,3-diene product formation from the 1-alkylcyclopropenes; this can be explained by either hyperconjugative stabilisation of the vinylcarbene intermediates involved in this pathway, or their differing propensities to 1,2 H-shift. The observed large variations in product distribution amongst these four cyclopropenes is interpreted in terms of these specific effects on individual pathways.
Kinetic Investigation of the Reactions of Methyl Radicals with But-2-yne
Claus, P.,Marquardt, M.,Trung, Tran Kim,Scherzer, K.
, p. 533 - 539 (2007/10/02)
The reactions of methyl radicals with but-2-yne have been studied in a greaseless static vessel in the temperature range 543...583 K.The methyl radicals were generated by thermolysis of azomethane (initial pressures 2.66 kPa and 3.19 kPa) in mixtures with the alkyne (initial pressures 0...7.8 kPa).The primary steps are H-abstractions producing 3-methylpropargyl radicals and additions to the triple bond forming trimethylvinyl radicals.Both radicals were stabilized by hydrogen abstraction from the parent compounds and by combination processes. The temperature dependence of the rate constant k2 for the addition reactio n can be expressed by the equation k2 = 108.65+/-0.20exp(-40300 +/- 1300)Jmol-1/RT M-1s-1 For the rate constant of hydrogen abstraction a value of k1 = 1.65 . 105 M-1s-1 at 573 K was estimated.Therefore the H-abstraction proceeds about two times faster than the addition reaction.
