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1.
Dr. Agnes Kütt Prof. Dr. Gunnar Jeschke Dr. Lauri Toom Dr. Jaak Nerut Prof. Christopher A. Reed 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8871-8874
Hydride abstraction from diarylamines with the trityl ion is explored in an attempt to generate a stable diarylnitrenium ion, Ar2N+. Sequential H-atom abstraction reactions ensue. The first H-atom abstraction leads to intensely colored aminium radical cations, Ar2NH.+, some of which are quite stable. However, most undergo a second H-atom abstraction leading to ammonium ions, Ar2NH2+. In the absence of a ready source of H-atoms, a unique self-abstraction reaction occurs when Ar=Me5C6, leading to a novel iminium radical cation, Ar=N.+Ar, which decays via a second self H-atom abstraction reaction to give a stable iminium ion, Ar=N+HAr. These products differ substantially from those derived via photochemically produced diarylnitrenium ions. 相似文献
2.
We consider site percolation on Z
d, directed edges going from any sZ
d to s+A
1,..., s+A
n, where A
1,..., A
n are the same for all sites and at least two of them are noncollinear. A site is closed if it belongs to p+Block, where p is a point in a Poisson distribution in R
dZ
d with a density and Block={sL: |s|M}+{sR
d: |s|}, where L is a linear subspace of R
d, |·| is the Euclidean norm, =max(|A
1|,..., |A
n|) and M is a parameter. We study the behavior of *, the critical value, and P
closed*, corresponding critical percentage of closed sites, when M. Denote R
d/L the factor space. Call two nonzero vectors U, V codirected if U=kV, where k>0. Theorem. If there are A
i and A
j whose projections to R
d/L are not codirected, then *1/M
dim(L) and P
closed* remains separated both from 0 and 1 when M. If projections of all A
1,..., A
n to R
d/L are codirected, then *1/M
dim(L)+1 and P
closed*1/M when M. 相似文献
3.
André Toom 《Journal of statistical physics》2007,129(3):555-566
We prove the existence of an invariant measure for a large class of random processes with discrete time without assuming their
linearity. Our main examples are “processes with variable length”, in which components may appear and disappear in the course
of functioning. One of these examples displays non-uniqueness of invariant measure in a 1-D process. 相似文献
4.
An efficient and general approach for the synthesis of amphiphilic 1,2-amino alcohols is reported. The use of N-benzyl protecting groups is essential for obtaining good yields when opening a long-chain terminal epoxide with an amine. 相似文献
5.
André Toom 《Bulletin of the Brazilian Mathematical Society》2002,33(3):419-425
We present a new class of one-dimensional particle systems, in which the number of components may change in the process of
interaction. We suggest that some of these systems display spontaneous symmetry breaking.
Received: 16 August 2002 相似文献
6.
7.
Kütt A Movchun V Rodima T Dansauer T Rusanov EB Leito I Kaljurand I Koppel J Pihl V Koppel I Ovsjannikov G Toom L Mishima M Medebielle M Lork E Röschenthaler GV Koppel IA Kolomeitsev AA 《The Journal of organic chemistry》2008,73(7):2607-2620
A general route to functionalized pentakis(trifluoromethyl)phenyl (C6(CF3)5) derivatives, promising building blocks for designing novel stable carbenes, radical species, superacids, weakly coordinating anions and other practically and theoretically useful species, is presented. This pertrifluoromethylation route proceeds via conveniently pregenerated (trifluoromethyl)copper (CF3Cu) species in DMF, stabilized by addition of 1,3-dimethyl-2-imidazolidinone (DMI). These species react with hexaiodobenzene at ambient temperature to give the potassium pentakis(trifluoromethyl)phenoxide along with hexakis(trifluoromethyl)benzene and pentakis(trifluoromethyl)benzene in a combined yield of 80%. A possible reaction pathway explaining the formation of pentakis(trifluoromethyl)phenoxide is proposed. Pentakis(trifluoromethyl)phenol gives rise to easily functionalized pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)aniline. Pertrifluoromethylation of pentaiodochlorobenzene and pentaiodotoluene allows straightforward access to pentakis(trifluoromethyl)chlorobenzene and pentakis(trifluoromethyl)toluene, respectively. XRD structures of several C6(CF3)5 derivatives were determined and compared with the calculated structures. Due to the steric crowding the aromatic rings in all C6(CF3)5 derivatives are significantly distorted. The gas-phase acidities (Delta Gacid) and pKa values in different solvents (acetonitrile (AN), DMSO, water) for the title compounds and a number of related compounds have been measured. The origin of the acidifying effect of the C6(CF3)5 group has been explored using the isodesmic reactions approach. 相似文献
8.
Toom L Kütt A Kaljurand I Leito I Ottosson H Grennberg H Gogoll A 《The Journal of organic chemistry》2006,71(19):7155-7164
Basicity constants for a series of 3,7-diazabicyclo[3.3.1]nonane derivatives in acetonitrile with a variation over 13 orders of magnitude have been determined using a spectrophotometric titration technique. An excellent correlation between basicity and calculated proton affinities obtained at PCM-B3LYP/6-31+G(d)//B3LYP/6-31G(d) level was found. The results are discussed in terms of substituent effects and compared to (15)N NMR chemical shifts. 相似文献
9.
Effect of strain on gas‐phase basicity of (E)‐1‐methyl‐2‐(1‐methyl‐2‐adamantylidene)adamantane 下载免费PDF全文
Ott Kekišev Ivari Kaljurand Lauri Toom Dieter Lenoir Peeter Burk Jaak Järv 《Journal of Physical Organic Chemistry》2015,28(7):447-451
Steric strain, caused by forced deformation of double bond geometry, has significant impact on alkene reactivity, as was shown by a study of the gas‐phase basicity of (E)‐1‐methyl‐2‐(1‐methyl‐2‐adamantylidene)adamantane. The Gibbs free energy of the strain effect in this compound was 42 kJ/mol. This analysis was made based on adamantylideneadamantane as a congeneric reference compound with a planar double bond. It was concluded that gas‐phase basicity could serve as a valuable alternative indicator for quantification of steric strain in alkenes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
T. Kaljuvee M. Toom A. Trikkel R. Kuusik 《Journal of Thermal Analysis and Calorimetry》2007,88(1):51-58
The extensive use of fossil fuels in energy production causes serious
pollution of atmosphere with SO2, CO2,
NOx, etc. In Estonia the electricity production is
based mainly on the pulverized firing (PF) of low-grade local fuel –
Estonian oil shale (EOS) which is characterized by a low calorific value (~9
MJ kg–1) and a high content of mineral matter
(65–70%) from which approximately 50% are carbonates. Since 2004, also
two boilers based on circulating fluidized bed combustion (CFBC) of EOS are
in exploitation.
The present study is focused on the comparative
investigation of the efficiency of different ashes collected from different
technological points of CFB and PF boilers as sorbents for SO2.
The influence of experimental temperature on the SO2-binding
characteristics of ashes as well as the possibilities of activation of ashes
(grinding, hydration) were investigated. It was shown that the SO2-binding
capacity of initial ashes at 700°C and p(SO2)=190
mm Hg was for CFBC ashes 24–30 mg and for PF ashes 10–23 mg SO2
per 100 mg sample, the best binding capacities belonging to economizer ash
(ECOA) and electrostatic precipitator ash from the 1st field (PESPA1f), respectively.
However, during initial stage of binding the best results were obtained with
air pre-heater ash (PHAA) and ESPA1f (both CFBC ashes). Grinding improved
the SO2-binding ability, being the most effective in
the case of bottom ash (BA) from CFBC and cyclone ash (PCA) from PF –
increase in binding capacity 2 and 2.3 times, respectively. As compared to
initial CFBC ashes, the binding characteristics of PF ashes remained lower
even after grinding. Hydration and previous calcination improved the binding
characteristics only of PF ashes. Hereby, the SO2-binding
ability of CFBC ashes is better than of PF ashes and they are more promising
sorbents for acidic gases, for example, for sulphur dioxide. 相似文献