Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

• Qing Yin,
• Qi Chen,
• Li-Can Lu and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 1212–1221, doi:10.3762/bjoc.13.120

• of 4-NP at time t, and k is the first-order rate constant. Figure 5b shows the ct/c0 and ln(ct/c0) changes with time for the reduction of 4-NP in the presence of NaBH4 with the AgNPs/SugPOP-1 composite as catalyst. By the Beer–Lambert law we find that ct/c0 is proportional to At/A0. At/A0 was

• calculated via the corresponding absorbance ratio of the absorption at 400 nm. There is obviously a linear relationship consistent with the pseudo-first-order kinetics between ln(ct/c0) and reaction time (t). The rate constant k of the reaction in the presences of the AgNPs/SugPOP-1 composite was 0.307 min−1

Membrane properties of hydroxycholesterols related to the brain cholesterol metabolism

• Malte Hilsch,
• Ivan Haralampiev,
• Peter Müller,
• Daniel Huster and
• Holger A. Scheidt

Beilstein J. Org. Chem. 2017, 13, 720–727, doi:10.3762/bjoc.13.71

• hydroxycholesterol also influences their impact on membrane permeability. For cholesterol, the induced membrane condensation causes a decreased penetration of polar molecules, e.g., water, across the membrane. This was proven here by measuring the permeation of dithionite across LUV membranes. The rate constant of

Structure–efficiency relationships of cyclodextrin scavengers in the hydrolytic degradation of organophosphorus compounds

• Sophie Letort,
• Michaël Bosco,
• Benedetta Cornelio,
• Frédérique Brégier,
• Sébastien Daulon,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2017, 13, 417–427, doi:10.3762/bjoc.13.45

• 4. Synthesis of compound 5 (Tr = trityl). Estimated pseudo-first-order rate constant (k) and amount (%) of hydrolyzed methyl paraoxon over the first 4 minutes.a Estimated pseudo-first-order rate constant (k) and amount (%) of hydrolyzed methyl parathion over the first 4 minutes.a Supporting

Synthesis and optical properties of new 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles

• Anastasia S. Kostyuchenko,
• Tatyana Yu. Zheleznova,
• Anton J. Stasyuk,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2017, 13, 313–322, doi:10.3762/bjoc.13.34

• the case of 15f,g (Figure 2). The measured photoluminescence quantum yields decrease in the following order: 15b (0.84) > 15d (0.49) > 15g (0.29) > 15e (0.25) > 15c (0.20) ≈ 15f (0.18), indicating that for larger substituents the non-radiative rate constant increases. Such phenomena are frequently

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• , temperature gradients, starting concentration and residence times, against a reaction conversion model enables the reaction order, rate constant, Arrhenius parameters, pre-exponential factor, and activation energy values to be determined in a rapid manner from one single flow experiment. The two latter

Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications

• Srikala Pangannaya,
• Neethu Padinchare Purayil,
• Shweta Dabhi,
• Venu Mankad,
• Prafulla K. Jha,
• Satyam Shinde and
• Darshak R. Trivedi

Beilstein J. Org. Chem. 2017, 13, 222–238, doi:10.3762/bjoc.13.25

• . Keywords: colorimetric sensor; DFT; molecular logic gates; rate constant; substituent effect; Introduction The development of new organic receptors for the detection of anions is of key interest to supramolecular chemists owing to the biological and environmental importance of anions [1][2][3][4][5][6][7

• min) [40]. The rate constant was calculated for R1 and R2 as a comparison over the reactivity of receptors towards acetate ions. The rate constant was calculated at two different wavelengths corresponding to the original absorption band of the free receptors and the red-shifted bands observed in the

• relative dependence of the anion concentration on the reacting species. Similarly, the rate constants have been calculated for R1 and R2 in the presence of fluoride. The lower order of magnitude of the rate constant in the presence of F− ions could be correlated to the pKa value of 3.2 (F− ion) in

Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy

• Monica Ferro,
• Franca Castiglione,
• Nadia Pastori,
• Carlo Punta,
• Lucio Melone,
• Walter Panzeri,
• Barbara Rossi,
• Francesco Trotta and
• Andrea Mele

Beilstein J. Org. Chem. 2017, 13, 182–194, doi:10.3762/bjoc.13.21

• of the of cross-polarization contact time, t, is expressed as follows (Equation 1): where kIS is the rate constant for the “heat flow” between the I and S spins, and kI, kS are the inverse of the spin-lattice relaxation times in the rotating frame for the spin I (T1ρ(H)) and S (T1ρ(S)), respectively

• . The simplified Equation (2) is obtained assuming that: 1) kS < kIS (kS is negligible), 2) kIS + kS > kI, the system is in the fast CP regime. According to Equation 2, the magnetization of the S spins rises with the CP rate constant kIS, reaches the maximum SCPMAX at time tMAX and, subsequently

Self-optimisation and model-based design of experiments for developing a C–H activation flow process

• Alexander Echtermeyer,
• Yehia Amar,
• Jacek Zakrzewski and
• Alexei Lapkin

Beilstein J. Org. Chem. 2017, 13, 150–163, doi:10.3762/bjoc.13.18

• rate constant k3 in Scheme 2. Empirical information provided constraints of process conditions, such as temperature and concentration ranges, whereas initial values of kinetic parameters were estimated based on a DFT model. Further details can be found in Supporting Information File 1. Here we

• stoichiometric coefficients of a compound i in the reaction j, ci denotes the molar concentration of the compound i, kj represents the reaction rate constant of the reaction j and ni,j gives the order of the reaction. All reaction steps in Scheme 2 were found to be first order with respect of the participating

Diels–Alder reactions of myrcene using intensified continuous-flow reactors

• Christian H. Hornung,
• Miguel Á. Álvarez-Diéguez,
• Thomas M. Kohl and
• John Tsanaktsidis

Beilstein J. Org. Chem. 2017, 13, 120–126, doi:10.3762/bjoc.13.15

• its higher boiling point. Figure 1b shows the influence of temperature and the ratio of starting materials. These experiments also showed trends as were expected. Values for the reaction rate constant, k, calculated from these experiments, are presented in Table 2 and are within expected limits when

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• recognition site is introduced to a reversible addition–fragmentation chain transfer (RAFT) polymerization system [65][66][67][68][69]. We have synthesized a chain transfer agent (CTA) bearing the CD moiety (CD-CTA) and have investigated this agent’s polymerization behavior. The polymerization rate constant

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

• Sonia L. Repetto,
• James F. Costello,
• Craig P. Butts,
• Joseph K. W. Lam and
• Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

• , the complications attending the use of buffered systems (and potential k3 catalysis by A−) are circumvented by using mineral acid (i.e., HCl, where [H+] was confirmed via the measurement of [Cl−] using ion chromatography). The observed rate constant for hydrolysis increases linearly with increasing

Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems

• Fabrizio Palumbo,
• Francisco Bosca,
• Isabel M. Morera,
• Inmaculada Andreu and
• Miguel A. Miranda

Beilstein J. Org. Chem. 2016, 12, 1196–1202, doi:10.3762/bjoc.12.115

• biradical species. Indeed, the coupling rate constant (kd2) should be similar to that of KP-α-Ch and therefore much higher than the hydrogen abstraction rate constant (kH), which is by definition lower than kiq. Consequently, biradicals are not expected to accumulate since their consumption is much faster

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time ¹³C CP-MAS solid-state NMR characterization

• Isabelle Mallard,
• Davy Baudelet,
• Franca Castiglione,
• Monica Ferro,
• Walter Panzeri,
• Enzio Ragg and
• Andrea Mele

Beilstein J. Org. Chem. 2015, 11, 2785–2794, doi:10.3762/bjoc.11.299

• -polarization rate constant, TCH−1. At long contact times, the 13C magnetization follows an exponential decay described by the proton relaxation time in a rotating frame, T1ρ. The combination of these factors leads to the general law for signal intensity reported in Equation 1: Equation 1 describes the time

• of magnitude, it is possible to resolve T1ρ and TCH parameters separately from the logarithmic plot of the CP intensity against the contact time. The CP rate constant TCH−1 can be easily extracted from the build-up curves and contains structural and dynamical information. This parameter mainly

Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors

• A. John Blacker and
• Katherine E. Jolley

Beilstein J. Org. Chem. 2015, 11, 2408–2417, doi:10.3762/bjoc.11.262

• widely studied by both modelling and experiment [28][29]. The rate of reaction of NaOCl and amines at high pH is very fast with a second order rate constant, kobs of 1.52 × 105 L·mol−1·min−1 reported for dimethylamine [30]. In this case it is the rate of mass transfer of the reagents, partitioned between

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• of the kinetic equations for this case is given by the expressions that are similar to Equation 2 up to replacing k1 with k2, k1d with k2d, and c1 with c2, cp = 0.575 mol/L. The rate constant k2 was found by fitting the whole c0(t) curve to the experimental data, whereas for k2d we focused on the

• interacting polymer-bound carbene and the last two indices designate the type of a dyad containing a reacting C=C bond) unknown and only one “new” (t) function available for fitting. Therefore we will search for the highest rate constant k211 that describes the attack of a [Ru]=PNB carbene onto a PCOE chain

• , as discussed above. We also assume that the rate constant k122 responsible for the interaction of a [Ru]=PCOE carbene with a PNB chain is a hundred times smaller than k211, by analogy with ca. hundred times smaller reaction rate of Gr-1 with PNB than that of Gr-1 with PCOE. In this manner we take

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• propagation rate (kp) and the initiation rate constant (ki), provided that no secondary metathesis occurs. In this case, Mn is only dependent on ki, because in all cases the same propagating species occurs and kp is the same. Accordingly, initiator 14 exhibits the highest initiation efficacy and initiator 5a

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• ) and the contribution of side reactions is minimal and can be neglected. For that reason, model 1 enables obtaining the absolute value of inhibition rate constant kA (the key reaction of inhibited oxidation). It is noteworthy that the kA values of dimers 6 and 9 are equal as a result of their similar

Preparation and evaluation of cyclodextrin polypseudorotaxane with PEGylated liposome as a sustained release drug carrier

• Kayoko Hayashida,
• Taishi Higashi,
• Daichi Kono,
• Keiichi Motoyama,
• Koki Wada and
• Hidetoshi Arima

Beilstein J. Org. Chem. 2014, 10, 2756–2764, doi:10.3762/bjoc.10.292

• time t, Q0 is the initial amount of drug in the γ-CD PPRX and k0 is the zero order release rate constant. First order kinetics where Qt is the amount of drug remaining in solid state at time t, Q0 is the initial amount of drug in the γ-CD PPRX and k1 is the first order release rate constant. Higuchi’s

• model where Qt is the amount of drug released in time t and kH is the Higuchi’s (release) rate constant. Hixson–Crowell model where Q0 is the initial amount of drug in the γ-CD PPRX, Qt is the amount of drug remaining in solid state at time t and kS is the Hixson–Crowell (release) rate constant

• . Korsmeyer–Peppas’s model where Mt/M∞ is fraction of drug release at time t, kP is the release rate constant, and n is the release exponent. Data analysis Data were given as the mean ± S.E. The statistical significance of mean coefficients for the studies was performed by analysis of variance followed by

Synthesis of nanodiamond derivatives carrying amino functions and quantification by a modified Kaiser test

• Gerald Jarre,
• Steffen Heyer,
• Elisabeth Memmel,
• Thomas Meinhardt and
• Anke Krueger

Beilstein J. Org. Chem. 2014, 10, 2729–2737, doi:10.3762/bjoc.10.288

• , and the rate constant of the reaction depends on the hydrindantin concentration in a complex manner – emphasizing its role as an important intermediate [26][27]. Moore and coworkers reported that in the event of insufficient amounts of reducing agent the formation of the coloured species is too low

Gold(I)-catalysed synthesis of a furan analogue of thiamine pyrophosphate

• Amjid Iqbal,
• El-Habib Sahraoui and
• Finian J. Leeper

Beilstein J. Org. Chem. 2014, 10, 2580–2585, doi:10.3762/bjoc.10.270

• of these two phases (k1) cannot be measured accurately from this data as it is almost all over within the first minute at all but the lowest concentrations of inhibitor. However, an estimated value of the second order rate constant kon for the initial binding of 17 is ca. 1 µM−1 min−1. The apparent

• equation with an apparent first order rate constant of 0.13 h−1. Using the ratio of recovered activity over unrecovered activity at equilibrium (8.5:91.5), the relative concentrations of ThDP and inhibitor (1000:1) and the previously reported KD value for ThDP (0.35 µM) [39], one can calculate that the Ki

Microsolvation and sp²-stereoinversion of monomeric α-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR

• Rudolf Knorr,
• Monika Knittl and
• Eva C. Rossmann

Beilstein J. Org. Chem. 2014, 10, 2521–2530, doi:10.3762/bjoc.10.263

• THF, so that its pseudo-first-order rate constant kψ in Equation 2 is the product of a second-order rate constant k0 and the constant concentration of free THF. One might be tempted to call on Equation 2 for interpreting the twofold increase of kψ that was observed for 4 in a more concentrated (85% in

Photo, thermal and chemical degradation of riboflavin

• Muhammad Ali Sheraz,
• Sadia Hafeez Kazi,
• Sofia Ahmed,
• Zubair Anwar and
• Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

• formed have been identified [85]. An attempt has been made to correlate the rate constant of anaerobic photolysis of FMF with solvent viscosity. A linear relationship has been observed between the second-order rate constants and inverse of solvent viscosity [32]. The dependence of flavin triplet state

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• and the electron acceptor must be chosen such that is negative enough to obtain a high electron transfer rate constant. The third electron transfer step is the unwanted back electron transfer BET within the contact ion pair (PS•+···A•−) which leads to initial reactants. This one is the more tricky to

• rate constants of singlet and triplet state deactivation to the ground state, respectively; kISC the rate constant of the intersystem crossing from 1PS to 3PS; 1kq/A, 3kq/A, (1kq/D, 3kq/D) the bimolecular electron transfer rate constant of the singlet and triplet excited state of the PS by the acceptor

• . Intersystem crossing rate constant kISC was obtained from the triplet state quantum yield and singlet state lifetime according to [59]: which leads to: and to At this RB concentration, and in the absence of quencher, the triplet state lifetime was measured around 80 µs, leading to kdes3= 1.25·104 M−1s−1

Chromatographically separable rotamers of an unhindered amide

• Mario Geffe,
• Lars Andernach,
• Oliver Trapp and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63

• slope of the linear regression equates the rate constant k1 for a first order interconversion and by using the Eyring equation (with R = gas constant, T = temperature, h = Planck constant, kB = Boltzmann constant) the rotational barrier was calculated to ΔG‡ (293 K) = 92.4 ± 0.1 kJ/mol (Z to E) and ΔG