35730-02-0Relevant articles and documents
Unsurpassed cage effect for the photolysis of dibenzyl ketones in water-soluble dendrimers
Yuan, Zhao,Chen, Jinping,Zeng, Yi,Li, Ying-Ying,Han, Yongbin,Li, Yi
experimental part, p. 6256 - 6264 (2011/10/09)
Amphiphilic water-soluble poly(alkyl aryl ether) dendrimers Gn (n = 1-3) with charge-neutral tetraethylene glycol monomethyl ethers at their periphery were synthesized as microreactors to control the photochemical reactions of dibenzyl ketone derivatives in aqueous solutions. Photophysical studies demonstrated that Gn can encapsulate organic molecules and provide a hydrophobic microenvironment. The product distribution of photolysis of dibenzyl ketone derivatives can be successfully controlled by encapsulating the substrates within dendrimers, and an unsurpassed cage effect of 1.00 is reached in high generation dendrimers, revealing that a thick and compact "shell" was formed at the periphery of the dendrimers. The cage effect is also significantly influenced by the substituent at the para-position of the guest molecules. The higher generation dendrimers exhibit a better confined microenvironment and the aggregates possess more compact cavities to "lock" the guests than the corresponding unimolecular dendrimers. After photolysis, the separation of products can be easily achieved by extracting from the dendrimer solutions and the dendrimers are simply recovered and reused.
Photolysis of 5,5-dibenzyl-Δ3-1,3,4-oxadiaiolines
Warkentin, John,Woollard, John McK.R.
, p. 289 - 307 (2007/10/03)
Photolysis of dibenzyl-Δ3-1,3,4-oxadiazolines (3) in the presence of dimethyl acetylenedicarboxylate (DMAD) gives only modest yields of the expected symmetrical 3,3-dibenzylcyclopropenes (4), but these are accompanied by more than six by-products, including unsymmetrical cyclopropenes, methylenecyclopropanes, and various pyrazoles. The origin of this array of products can be explained by a series of steps starting with photolysis of 3 to form a diazoalkane that undergoes 1,3-dipolar cycloaddition to DMAD, generating a 3H-pyrazole as initial product. The latter is further photolyzed to a symmetrical cyclopropene in competition with benzyl group migration by thermal 1,5-sigmatropic or ion-pair rearrangement to afford a 4H-pyrazole. The 4H-pyrazole in turn undergoes photolysis to an unsymmetrical cyclopropene, which rearranges to a methylenecyclopropane. The 4H-pyrazole also undergoes autoxidation, in the presence of air, to afford a benzoyl-4H-pyrazole. Additionally, in competition with rearrangement, the various pyrazoles lose a benzyl group or a methoxycarbonyl group to afford pyrazoles with one less substituent.
ELECTRONIC EFFECTS ON CARBON-CHLORINE BONDS
Warnhoff, E. W.,Nakamura, Akira
, p. 503 - 506 (2007/10/02)
For the first time a reaction has been found to study electronic effects on C-Cl bonds in an equilibrium situation.The reaction, the α α' rearrangement of α-chlorodibenzyl ketones, correlates well with the difference in Taft ? deg values with ρ +0.75.
Micellar Systems as ''Supercages'' for Reactions of Geminate Radical Pairs. Magnetic Effects
Turro, Nicholas J.,Weed, Gregory C.
, p. 1861 - 1868 (2007/10/02)
The photochemistry of dibenzyl ketone (DBK) and other molecules capable of producing benzyl radicals and substituted benzyl radicals has been investigated in micellar systems.The cage effect (percent of unscavengeable radical pairs produced by photolysis) was measured under a variety of conditions, and the results are compared with those obtained in homogeneous organic solvents.For example, parameters such as mean occupancy of ketone, detergent type and concentration, O2 concentration, additives, temperature, applied magnetic field, and pressure have been varied and investigated as to their influence on the magnitude of cage effect.In addition to modifying its environment, structural modification of the DBK by incorporation of 2H and 13C isotopes, hydrophobic groups, and heavy atoms was performed to investigate the impact of these variations on the cage effect in micellar systems.Isotopic substitution of 2H or 13C leads to results on both the quantum yields for reactions and on the percent cage that were consistent with expectations of magnetic isotope effects.Hydrophobic groups substituted in the 4-position of DBK were found to cause a substantial increase in the cage effect and yet retain the magnetic-field-dependent character found in the parent DBK.Incorporation of Br in the 4-position of DBK was found to enhance the cage effect but at the same time cause the cage effect to become magnetic field independent.Substitution of α-naphthyl for phenyl in DBK also produced magnetic-field-independent behavior, in addition to a dramatic decrease in the efficiency of photolysis.
Methods employing magnetic isotope effect
-
, (2008/06/13)
Separation and enrichment of isotopes are effected and rates and products of reactions are controlled by methods employing magnetic isotope effect. By virtue of the invention, when dibenzyl ketone was photolyzed to partial conversion in a dimensionally restricted environment (micelles in soap solution) 13 C enrichment of over 100% was achieved. The 13 C enrichment was found to occur specifically at the carbonyl carbon and to be magnetic field dependent.
