The Chemistry of Thujone. Part XIV.. Synthesis of biologically active aryl terpenoid analogues

Employing thujone-derived intermediates, a series of achiral ( 9a–d ; Scheme 1) and chiral ( 11b and 11d; Scheme 2) terpene analogues related to the biologically active ‘terpenoid’ hybrids have been prepared. The stereochemistry of the key epoxidation reaction was established by correlation of the product 11b with the previously reported alcohol (R)- 20 of known absolute configuration (Scheme 3).     

Aromatic Nucleophilic Substitution. Part 1. Regiospecific Substitution of the Nitro Groups in 3,5-Dinitrophthalic-Acid Derivatives

The regioselectivity of nucleophilic substitution of the nitro groups in 3,5-dinitrophthalic anhydrides and 3,5-dinitrophthalimides (Scheme) with a variety of nucleophiles (Nu^?) was studied. In all cases, the 3-nitro group was selectively substituted. With excess of the same nucleophilic reagent or with other nucleophiles, the 5-nitro group could subsequently be replaced.     

Dediazoniations of Arenediazonium Ions in Homogeneous Solution. Part XIV. 15N-CIDNP. Investigation of the reactions of diazonium ions in weakly alkaline aqueous solutions

¹⁵N-CIDNP. spectra recorded during the reaction of diazonium cations with OH^? in weakly alkaline aqueous solutions show that the dediazoniation is at least partially homolytic. The polarizations observed for the diazonium and trans-diazotate ions can be explained by reaction proceeding via a cage involving diazenyl and diazotate radicals using Kaptein's rules and simple intensity considerations.     

Investigations on the Reactivity of Fascaplysin,Part I,Aromatic Electrophilic Substitutions Occur at Position 9

Electrophilic aromatic substitutions, such as halogenation and sulfonation, occur primarily para to the indole N‐atom at C(9) of the unique 12H‐pyrido[1,2‐a:3,4‐b′]diindole ring system of fascaplysin.     

Nucleophilic displacement of aromatic fluorine. Part V. Use of nitrogen heterocycles as nucleophiles

The scope of the nucleophilic displacement of aromatic halogens on 1,4-benzodiazepine precursors by the anions of pyrroles, pyrazoles and imidazoles was studied both with and without electron-withdrawing substitutents on the heterocyclic nucleophiles. Some of the products proved to be useful intermediates for the synthesis of novel fused 1,4-benzodiazepines.     

Protein fouling in microfiltration: deposition mechanism as a function of pressure for different pH

The influence of applied pressure on the fouling mechanism during bovine serum albumin (BSA) dead-end microfiltration (MF) has been investigated for a polyethersulfone acidic negatively charged membrane (ICE-450) from Pall Co. BSA solutions at pH values of 4, 5 (almost equal to the protein isoelectric point, IEP), and 6 were microfiltered through the membrane at different applied transmembrane pressures. Results have been analyzed in terms of the usual blocking filtration laws and a substantial change in the fouling mechanism was observed as the pressure was increased, this change can be related to the specific membrane-protein and protein-protein interactions.     

Nucleophilic Addition to Acetylenes in Superbasic Catalytic Systems: XIV. Vinilation of Diols in a System CsF-NaOH

A new catalytic system CsF-NaOH was developed for the synthesis of mono- and divinyl ethers of alkanediols exceeding in efficiency KOH. The nucleophilic addition of diols to acetylene in the presence of this system occurs both at enhance pressure (without solvent, 140–160°C) and atmospheric pressure (in DMSO medium, 100°C) of acetylene. Conditions were established of a selective preparation in a high yield of divinyl ethers from diols.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 677–683.Original Russian Text Copyright © 2005 by Oparina, Khil’ko, Chernyshova, Shaikhudinova, Parshina, Preiss, Henkelmann, Trofimov.     

Computer simulation for the prediction of separation as a function of pH for reversed-phase high-performance liquid chromatography. II. Resolution as a function of simultaneous change in pH and solvent strength.

The optimization of reversed-phase high-performance liquid chromatographic separation by the simultaneous variation of pH and solvent strength (%B) was studied for acidic (substituted benzoic acids) and basic samples (substituted anilines). The combination of these two variables was expected to be more useful than either variable alone. This proved to be the case for the benzoic acid sample, but not for the aniline sample. Column plate numbers were also studied for each sample and as a function of pH. With the exception of one compound (3,5-dimethylaniline) in one particular pH range (3.0-4.5), plate numbers of 12,000-20,000 were observed for each sample.     

Degradation of floor adhesives as a function of pH

Floor adhesives on cement-based substrates may degrade if the pH is high enough and this has in many cases led to emissions of odorous substances and deteriorated indoor air quality. We have used isothermal calorimetry to assess the degradation rate of two floor adhesives as a function of pH. The rate of heat production measured by the calorimeter is proportional to the reaction rate. The degradation rate was similar for a “standard” and a “low emitting” adhesive, but the low emitting adhesive did not release volatile reaction products. The results show that adhesive degradation is strongly pH dependent. A model of alkaline hydrolysis based on two reaction sites is discussed.     

Kinetics of polydopamine film deposition as a function of pH and dopamine concentration: Insights in the polydopamine deposition mechanism

Highly ordered mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles has been successfully synthesized. By oxidative treatment using (NH(4))(2)S(2)O(8) and H(2)SO(4) mixed solution, numerous hydrophilic groups were created in the mesopores without destroying the ordered mesostructure of CMK-3. Through the in situ reduction in Fe(3+), magnetic nanoparticles were successfully introduced into the mesopores, resulting in the multifunctional mesoporous carbon Fe-CMK-3. The obtained hybrid carbon material possesses ordered mesostructure, high Brunauer-Emmett-Teller (BET) surface area up to 1013 m(2)/g, large pore volume of about 1.16 cm(3)/g, carboxylic surface, and excellent magnetic property. When used as an adsorbent, Fe-CMK-3 exhibits excellent performances for removing toxic organic compounds from waster-water, with a high adsorption capacity, an extremely rapid adsorption rate, and an easy magnetically separable process. In the case of requiring emergency removal of large amount of organic pollutants in aqueous, the hybrid carbon adsorbent would be an ideal choice.     

Cuprous Complexes and Dioxygen. Part 12.. Rate law and mechanism of the copper-catalyzed oxidation of ascorbic acid in aqueous acetonitrile

The copper-catalyzed oxidation of ascorbic acid (AscH₂) has been studied with a Clark electrode in aqueous MeCN. Cu^I or Cu^II may be equally used as the source of metal ion, without influence on the rate law. At sufficiently high [MeCN], the rate of the overall reaction is essentially given by the rate of Cu^I autoxidation: the reaction is of first order with respect to [Cu] and [O₂] and shows an inverse-square dependence on [MeCN] as observed for the autoxidation of Cu. The pH dependence is complicated by the combination of the intrinsic pH effect on autoxidation with an additional term in the rate law which is directly proportional to [AscH^?]. The latter term is explained by direct oxidation of the organic substrate by the primary dioxygen adduct of Cu^I, CuO. For [MeCN] < 0.7M , a gradual and pH-dependent transformation of this rate law and deviation from the first-order dependence on [O₂] is indicated.     

Kinetics and mechanism of oxidations by metal ions. Part 16. Oxidation of 4-oxopentanoic acid by aquomanganese(III) ions

Summary The outer-sphere oxidation of 4-oxopentanoic acid (4-OPA) to MeCO₂H by aquomanganese(III) ions exhibits a first-order dependence on [4-OPA] and [Mn(III)](aq). The observed pseudo first-order rate constant k _obs ([4-OPA] [Mn^III](aq)) is independent of [Mn^II] but decreases with increasing [H⁺]. The retarding effect of [H⁺] on the observed rate could be explained by considering either the reaction between MnOH⁺(aq) and MeCOCH₂— CH₂CO₂H or between Mn³⁺(aq) and MeCOCH₂CH₂-COO^– ions. The rate constant for the latter pair of reactants is much higher than the rate constant for the reaction between the first pair. Since the activation enthalpy for the first pair is about 14 kJ mol^–1 less than that of the second pair, it is concluded that the reactive species are MnOH²⁺(aq) and MeCOCH₂CH₂CO₂H or that the preferred oxidant is MnOH²⁺(aq) ion.     

Doublet-quartet conversion in negative ions as a possible mechanism of the electron autodetachment delay

Molecular negative ions with abnormally high lifetimes (20 micros) relative to electron autodetachment were registered at 1.65 eV electron energy in pyromellitic acid imide by means of negative ion mass spectrometry with resonant electron capture. Using quantum-chemical calculations, it was shown that the delay of the electron autodetachment may be caused by the conversion of an originally generated molecular ion-doublet into a molecular ion-quartet, as a result of intersystem crossing of the potential energy surfaces of these ions. It was noticed that the ion-quartet cannot decay rapidly into the molecule of the ground state because of the prohibition of the spin flip, which is similar to that for phosphorescence. It can also not decay into the parent triplets, because these triplets are higher in energy than the ion. As a whole, both prohibitions provide the observed effect of the high lifetime of the ions.     

J-aggregation of a sulfonated amphiphilic porphyrin at the air-water interface as a function of pH

π-A isotherms, ellipsometric measurements, Brewster angle microscopy (BAM) and reflection spectroscopy have been utilized to characterize the films of an amphiphilic porphyrin ((OD)(3)TPPS(3)) at the air-water interface as a function of pH. This porphyrin forms stable mono-molecular layers at such interfaces, and exhibits different J-aggregation as a function of pH. The J-aggregation of (OD)(3)TPPS(3) on neutral pH subphases is notable considering that the nitrogen atoms at the central macrocycle have a pK(a)≈4.9. The type of aggregates at neutral pH is like those detected at pH<4, because the central porphyrin ring is already protonated. However at basic pH the aggregation happens without protonation of the central ring but can be instead controlled by application of the surface pressure. At the air-water interface, (OD)(3)TPPS(3) shows two bands, a red component and a blue component, which have characteristics of non-degenerate linear oscillators being perpendicularly polarized between each other. The spectral behavior observed on subphases at different pHs is qualitatively interpreted by means of exciton coupling theory, assuming that the degenerate transitions attributed to the Soret band are split. Additionally, highly oriented molecular films of these J-aggregates were deposited onto transparent quartz slides.     

Polymerization of cyclic ethers in the presence of maleic anhydride. Part II. Investigation of the polymerization mechanism

In order to elucidate the reaction mechanism of both the radiation-induced and benzoyl peroxide-catalyzed polymerizations of cyclic ethers in the presence of maleic anhydride, the development of color during reaction and copolymerization of oxetane derivatives were investigated. Upon addition of a small amount of the γ-ray or ultraviolet-irradiated equimolar solution of a cyclic ether and maleic anhydride to isobutyl vinyl ether, a rapid polymerization took place, and the resulting polymer was confirmed to be a homopolymer of isobutyl vinyl ether. A heated solution of dioxane, maleic anhydride, and a small amount of benzoyl peroxide can initiate the polymerization of isobutyl vinyl ether in the same manner. The electrical conductivity of a 1:1 mixture of maleic anhydride and dioxane is increased by about a factor of ten after ultraviolet irradiation. These results indicate that some cationic species are actually formed in the system by irradiation or the decomposition of added benzoyl peroxide. The mechanism of formation of the cationic species responsible for the initiation may be explained as follows. A free radical of an ether is formed by abstraction of a hydrogen atom attached to the carbon adjacent to oxygen atom, followed by a one-electron transfer from the resulting radical to maleic anhydride, an electron acceptor, to yield the cationic species of the ether and the anion-radical of maleic anhydride, respectively. The resulting cationic species as well as the counteranion-radical are resonance-stabilized. Therefore, the present polymerization may be designated a radical-induced cationic polymerization.