135733-75-4Relevant academic research and scientific papers
Preassociation, free-ion, and ion-pair pathways in the electrophilic bromination of substituted cis- and trans-stilbenes in protic solvents
Ruasse, Marie-Fran?oise,Lo Moro, Giacomo,Galland, Bernard,Bianchini, Roberto,Chiappe, Cinzia,Bellucci, Giuseppe
, p. 12492 - 12502 (2007/10/03)
Rates and products of electrophilic bromination of ring-substituted cis- and trans-stilbenes have been investigated in acetic acid, trifluoroethanol, ethanol, methanol, and water-methanol mixtures. The mY(Br) relationships (linear for nucleophilic solvent
Different Reversibility of Bromonium vs β-Bromocarbonium Ions Formed during the Electrophilic Bromination of Substituted Stilbenes. Evidence for Rate Determination during the Product-Forming Step
Bellucci, Giuseppe,Bianchini, Roberto,Chiappe, Cinzia,Brown, Robert Stanley,Slebocka-Tilk, Henryka
, p. 8012 - 8016 (2007/10/02)
In order to check the relative reversibility of brominium and β-bromocarbonium ion formation, the product distributions of the reactions of Br2 with cis- and trans-stilbene (1b and 2b) and with their p-methyl (1a and 2a), p-(trifluoromethyl) (1c and 2c). and p,p′-bis(trifluoromethyl) derivatives (1d and 2d) in 1,2-dichloroethane have been determined in the 10-1-10-4 M concentration range. The rate constants (k3) for the bromination of these stilbenes at 25 °C spanned 7 orders of magnitude. The observed dibromide ratios showed that an open β-bromocarbonium ion was the intermediate of the bromination of 1a and 2a, whereas bridged or partially bridged ions were involved with all other olefins. In these cases, the extent of bridging increased, and equilibration to the more stable trans bromonium ion occurred at the lowest reagent concentrations to give the erythro (or meso) dibromide 3 as the main product. The increase in 3 was always accompanied by an increase in cis-trans olefin isomerization during the bromination of the cis olefin. This is attributed to a return of the trans bromonium ion to the corresponding olefin. This process was maximum with 1d, and minimum with 1a. It is concluded that, whereas the formation of the β-bromocarbonium ion intermediate is completely rate-determining in the case of 2a, both the formation of the trans bromonium ion and the following dibromide formation are partially rate-determining in the case of 2d.
Photolytic Dehydrochlorination of N-Chloro-N-alkyl Amides: Formaton of N-(α-Methoxyalkyl) Amides
Phan, Xuan T.,Shannon, Paul J.
, p. 5164 - 5170 (2007/10/02)
The photoinduced dehydrochlorination, in methanol, of N-chloro-N-alkyl amides with one substitient at the α position to nitrogen gave good yields of N-(α-methoxyalkyl) amides and the parent amides as secondary products.N-Chloro amides disubstituted at the α position gave mostly parent amides.In most cases no products resulting from 1,5 hydrogen transfer of amidyl radicals were observed.The quantum yields of decomposition of N-chloro-N-methylpentanamide (1a) were significantly greater than unity, indicative of a chain process for dehydrochlorination.The reaction was affected by the solvent, addition of base or radical inhibitors, concentration of N-chloro amide, light intensity, and irradiation wavelenght.
