640-21-1Relevant articles and documents
Solvent-free phase-vanishing reactions with PTFE (Teflon) as a phase screen
Pels, Kevin,Dragojlovic, Veljko
scheme or table, (2010/04/22)
In a solvent-free phase-vanishing reaction with PTFE (polytetrafluoroethylene, Teflon) tape as the phase screen, a thermometer adapter is utilized to insert a PTFE-sealed tube into the vapor phase above the substrate. Besides avoiding use of solvents, the experimental design is not dependent upon the densities of the reactants and the procedure generates little or no waste while providing the reaction products in high yield and in high purity.
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.
Manganese-medium Novel Debromination of Olefins with Tetradecyltrimethylammonium Permanganate and Trimethylbromosilane
Hazra, Braja G.,Chordia, Mahendra D.,Bahule, Bharat B.,Pore, Vandana S.,Basu, Sourav
, p. 1667 - 1670 (2007/10/02)
The synthetic utility of tetradecylammonium permanganate-trimethylbromosilane as an excellent new reagent for the stereo- and chemo-selective trans-dibromination of alkenes is reported.
Imidyl Radicals. The Chemistries of 1,8-Naphthalenedicarboximidyl and Phthalimidyl Radicals
Day, J. C.,Govindaraj, N.,McBain, D. S.,Skell, P. S.,Tanko, J. M.
, p. 4959 - 4963 (2007/10/02)
The chemistries of 1,8-naphthalenedicarboximidyl (N.) and phthalimidyl (P.) radicals are described.Hydrogen abstractions from alkanes and additions to olefins and benzene proceed in high yield.The low cost of phthalimide, coupled with the absence of a parasitic ring-opening reaction for P., makes N-bromophthalimide an economical reagent for low-selectivity brominations.The chemistry of N. resembles that of other imidyl radicals (succinimidyl, glutarimidyl) with respect to selectivities.Conversely, P. is somewhat of a maverick among imidyl radicals, being slightly more selective in its reactions, but still 102-103 less selective than Br..
Bromochlorination of Alkenes with Dichlorobromate (1-) ion. IV. Regiochemistry of Bromochlorinations of Alkenes with Molecular Bromine Chloride and Dichlorobromate (1-) Ion
Negoro, Takeshi,Ikeda, Yoshitsugu
, p. 2547 - 2552 (2007/10/02)
The regioselectivity of the addition of molecular bromine chloride to alkenes is dependent on both the steric and electronic effects of the alkyl substituent.In contrast, the regioselectivity of the addition of dichlorobromate (1-) ion to alkenes is controlled mainly by the steric effect of the substituent.
THE ELECTRON SPIN RESONANCE SPECTRA OF THE ANNULENE (CYCLOBUTADIENE) RADICAL CATIONS, R4C4+.
Courtneidge, John L.,Davies, Alwyn G.,Lusztyk, Ewa,Lusztyk, Janusz
, p. 155 - 164 (2007/10/02)
A series of simple (R=R') and mixed (RR') cyclobutadiene radical cations, R2R'2C4+., have been prepared by photolysis of the alkynes, RCCR' or of mixtures of the alkynes RCCR and R'CCR', in dichloromethane in the presence of aluminium chloride, and the e.s.r. spectra have been recorded.The magnitude of the 13C hyperfine coupling in Et4C4+. confirms that it is a ?-radical, with no evidence for out-of-plane or in-plane (Jahn-Teller) distortion.The values of a(Hβ) for the radicals (RCH2)4C4+. and (RCH2)2R'2C4+. indicate that, as the bulk of the alkyl substituents increases, the group R is pushed out of the plane of the ring.Some unusual temperature effects on a(Hβ) are ascribed to interaction of the radical cation with the solvent or with the counterion.As the bulk of the alkyl groups increases, the g-value decreases from 2.0030 to about 2.0022. cis- and trans-Isomers of the radicals Me2tBu2C4+., Et2tBu2C4+., iBu2tBu2C4+., and propably Me2Et2C4+. have been identified, and the spectra of cis- and trans-Me2tBu2C+. are analysed in terms of breaking of the degeneracy of the molecular orbitals of the cyclobutadiene system by differential electron release by the alkyl groups (tBu > Me).
Reactions of a Graded Set of Radicals with N-Bromosuccinimide; Two Transition States
Tlumak, Robert L.,Skell Philip S.
, p. 7267 - 7274 (2007/10/02)
The reactions of N-bromosuccinimide with a series of radicals have been studied.These reactions fall into two categories, the more reactive radicals producing ?-succinimidyl and the less reactive radicals producing ?-succinimidyl.The threshold for the changeover from one reaction domain to the other occurs with radicals less reactive than secondary alkyls.These results are interpreted with two transition states, an in-line transition state for the more reactive radicals and an out-of-plane transition state for the less reactive radicals. An upper limit of 18 kcal/mol is established for the enthalpy difference, HS? - HS?.Two new methods for generating S? radicals are indicated.
