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Search for "lifetime" in Full Text gives 161 result(s) in Beilstein Journal of Organic Chemistry.
Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes
Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78
- diradical intermediate of type 17, its lifetime is evidently too short to allow ring-expansion as depicted in Scheme 7. Whether this process might be induced thermally (vinylcyclopropane→cyclopentene rearrangement; [23]) is an open question. Conclusion Although the detailed mechanisms of the
The arene–alkene photocycloaddition
Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61
- intersystem crossing by the heavy-atom effect, and thus decreases the singlet excited-state lifetime of the arene. Mattay considered this as direct proof that the addition of benzene to 1,3-dioxoles takes place primarily via the singlet excited-state of benzene. Ferree et al. had earlier provided evidence
Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor
Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34
- %), τ2 = 7.76 ns (87.78%). The faster decay component (3.42 ns) is due to the anthracene moiety [47] and the relatively stable component with longer lifetime (7.76 ns) is attributed to the benzimidazolium motif of 1. However, in the presence of 1 equiv of H2PO4−, the lifetime of both the components
- marginally decreases (Table 2). In the presence of 2 equiv of H2PO4−, the lifetime of the anthracene component increases without showing any marked change in the pre-exponential factor. This was also true for the benzimidazolium component. Figure 13 shows the decay profiles. The change in the lifetimes of
Ene–yne cross-metathesis with ruthenium carbene catalysts
Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22
- . On the other hand, no improvement of stereoselectivity was obtained under these experimental conditions. It was shown that ethylene increased the lifetime of the Fischer carbene intermediate. Moreover, its role might consist in supporting the methylene transfer, thereby enhancing catalyst turnover
Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones
Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16
- triplet excited state is very fast, 1011 s−1 for benzophenones, and not affected by heavy atoms, but the ISC process of triplet benzophenones to singlet ground state would be accelerated, reducing lifetime of triplet benzophenones. Finally, triplet benzophenones with a short lifetime would give rise to a
Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers
Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130
- particles displayed an excitation lifetime 17 times longer than pyrene dissolved in THF. Metal-catalyzed polymerizations At the end of the last century, many groups focused their research on the production of polyolefins in aqueous media. Ethylene as one of the most industrially relevant monomers was
Solvent-free phase-vanishing reactions with PTFE (Teflon®) as a phase screen
Beilstein J. Org. Chem. 2009, 5, No. 75, doi:10.3762/bjoc.5.75
- (C6F14), has a high global warming potential (GWP ~10,000) and atmospheric lifetime of 3200 years [17]. In addition, some solvents, reagents and reaction products are partially soluble in FC-72 [13][14][15][16][18], which limits our ability to either reuse or recycle it. Ryu and Curran have reported
Gold film- catalysed benzannulation by Microwave- Assisted, Continuous Flow Organic Synthesis (MACOS)
Beilstein J. Org. Chem. 2009, 5, No. 35, doi:10.3762/bjoc.5.35
- lifetime and durability of the film under the optimized reaction conditions was examined. The transformation in Table 2, entry a was followed over the course of 2 h; reaction performance is optimal at the beginning and slowly, but steadily erodes. Visibly, the film darkens over time, which we attribute to
From discovery to production: Scale- out of continuous flow meso reactors
Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29
- catalyst was detected over the course of the cycles and ICP-ES studies showed the nickel content in the resin was the same as when the catalyst was initially prepared. An important point of concern when using heterogeneous catalyst is its lifetime, particularly for industrial and pharmaceutical
- carried out in a parallel channel meso reactor at a flow rate of 95 ml h−1. Kumada reaction carried out in a parallel channel meso reactor over a 31-hour period at a flow rate of 95 ml h−1 to show catalyst stability and lifetime. Kumada reaction carried out in a parallel channel meso reactor at a flow
The development and evaluation of a continuous flow process for the lipase- mediated oxidation of alkenes
Beilstein J. Org. Chem. 2009, 5, No. 27, doi:10.3762/bjoc.5.27
- activity, again illustrating that careful dosage of H2O2 (2) increased the operational lifetime of the biocatalyst. The authors also noted that the presence of EtOH and urea resulted in moderate deactivation of the enzyme. In 2006, Olivo and co-workers [21] reported an environmentally benign method for
- synthetically useful alkenes, whilst increasing the biocatalyst’s lifetime. With this in mind, our initial investigation into the development of a continuous process for the synthesis of epoxides focussed on the incorporation of immobilised Candida antarctica lipase B, Novozym® 435 (4), into a flow reactor and
Reversible intramolecular photocycloaddition of a bis(9-anthrylbutadienyl)paracyclophane – an inverse photochromic system. (Photoactive cyclophanes 5)
Beilstein J. Org. Chem. 2009, 5, No. 20, doi:10.3762/bjoc.5.20
- complete extinction (see Supporting Information p S2). The dissociation kinetics were found to be first order with a half-life of ca 3.8 h. This suggests a much longer lifetime at ambient temperature, as observed experimentally. 4 Structure of the photoproduct Preparative irradiation of a solution of 2 in
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