Continuous-flow catalytic esterification of free fatty acids (FFA) with methanol in the presence of sulfonated hydrothermal carbon (SHTC) as catalyst was studied. Using a Box-Behnken experimental design protocol, the effects of residence time, methanol:acid molar ratio, and water concentration on the conversion of oleic acid into methyl oleate were investigated. The optimum conditions for achieving esterification greater than 90 % at 100 degrees C were determined to be 11-minute residence time, a MeOH:FFA molar ratio >14.6 and up to 14.9 % water. The SHTC was used continuously for 4.5 days without a significant decrease in catalytic performance. The results confirmed that SHTC is an effective solid acid catalyst in a continuous flow system for the esterification of FFA.

Solid acid carbon catalysts were prepared by activating hydrothermal carbon with potassium hydroxide (KOH) to form high surface area carbon and using an environmentally benign L-cysteine method for subsequent sulfonation. The textural and physical properties of the solid acid catalysts were characterized by different techniques including Powder X-ray diffraction (PXRD), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, Scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) in order to understand the functionalization of sulfonic acids on the carbon support. The catalytic activity of the carbon-based materials towards biofuel production was studied by using the esterification of oleic acid as a prime example. A quantitative yield of 95 % fatty acid methyl ester was achieved using the high surface area sulfonated catalyst (HSC-SO3H with SA=1751 m(2)/g) at 80 degrees C for 4 hours at 1 atm with 10 wt. % of catalyst loading and at a 10 : 1 molar ratio of methanol/oleic acid. Sulfonation of carbon with L-cysteine represents a promising technique to obtain solid acid catalysts, which are expected to be useful for other applications in Lewis-acid catalysis, separations, and beyond.

The Riemann hypothesis is arguably the most important unsolved problem in mathematics. It is even difficult to state to beginning students since it requires a knowledge of the zeta function for complex values of the argument. However, there are at least 23 equivalent statements of this hypothesis that are much easier to state. In this paper we examine one such idea called the Landau hypothesis. This Landau hypothesis has a very simple interpretation in terms of the prime factorization of integers. Surprisingly this hypothesis also has a useful description in terms of a one dimensional random walk. We show by means of a known, but not often seen, integral representation for any Dirichlet series that the Landau hypothesis implies the Riemann hypothesis.

In the colloidal synthesis of inorganic perovskite materials, cesium oleate (CsOL) is the most commonly used Cs precursor. Yet, despite its ubiquitous use in literature, CsOL has been observed to be insoluble at room temperature and leads to surprisingly inconsistent results in CsPbX3 nanocrystal synthesis, depending on the Cs salt from which the precursor is derived. We show that under the conditions used in most reports, the amount of oleic acid (OA) added, while stoichiometrically sufficient, still leads to incomplete conversion of the Cs salts to CsOL. This results in a mixture of Cs sources being present during the reaction, causing decreased homogeneity and reproducibility. When a 1:5 Cs:OA ratio is used, complete conversion is readily obtained, even under mild conditions, resulting in a precursor solution that is soluble at room temperature and yields identical synthetic results, regardless of the initial Cs source. Furthermore, H-1 nuclear magnetic resonance (NMR) of solutions prepared using varying Cs:OA ratios shows that the maximum ratio of Cs:OA obtainable in solution is 1:5, with any excess Cs present in the precipitate. We believe the use of a soluble, fully converted CsOL reagent will improve reproducibility for Cs-based perovskite synthesis and directly benefit synthetic methods based on microfluidics.

Here, we report two methods that chemically modify alginate to achieve neutral-basic pH sensitivity of the resultant hydrogel. The first method involves direct amide bond formation between alginate and 4-(2-aminoethyl)benzoic acid. The second method that arose out of the desire to achieve better control of the degradation rate of the alginate hydrogel involves reductive amination of oxidized alginate. The products of both methods result in a hydrogel vehicle for targeted delivery of encapsulated payload under physiological conditions in the gastrointestinal tract. Two-dimensional diffusion-ordered spectroscopy and internal and coaxial external nuclear magnetic resonance standards were used to establish chemical bonding and percent incorporation of the modifying groups into the alginate polymer. The hydrogel made with alginate modified by each method was found to be completely stable under acidic pH conditions while disintegrating within minutes to hours in neutral-basic pH conditions. We found that, while alginate oxidation did not affect the β-d-mannuronate/α-l-guluronate ratio of alginate, the rate of disintegration of the hydrogel made with oxidized alginate was dependent upon the degree of oxidation.

Many inexpensive biofuel feedstocks, including those containing free fatty acids (FFAs) in high concentrations, are typically disposed of as waste due to our inability to efficiently convert them into usable biofuels. Here we demonstrate that carbon derived from waste tires could be functionalized with sulfonic acid (-SO3H) to effectively catalyze the esterification of oleic acid or a mixture of fatty acids to usable biofuels. Waste tires were converted to hard carbon, then functionalized with catalytically active -SO3H groups on the surface through an environmentally benign process that involved the sequential treatment with L-cysteine, dithiothreitol, and H2O2. When benchmarked against the same waste-tire derived carbon material treated with concentrated sulfuric acid at 150 degrees C, similar catalytic activity was observed. Both catalysts could also effectively convert oleic acid or a mixture of fatty acids and soybean oil to usable biofuels at 65 degrees C and 1 atm without leaching of the catalytic sites.

89Zr–Tetraazamacrocycle complexes display extraordinary stability.

We describe herein a general and efficient synthetic approach toward substituted pyridines from functionalized N-acy1-2,3-dihydropyridones in two steps; 1,2-addition with organocerium reagents and subsequent oxidative aromatization with chloranil. This strategy allows the generation of pyridines with various substitution patterns and introduces a variety of substituents including aryl, alkyl, alkynyl, alkenyl, and heteroaryl groups at the desired positions. Published by Elsevier Ltd.

We describe herein a general and efficient synthetic approach toward substituted pyridines from functionalized N-acyl-2,3-dihydropyridones in two steps; 1,2-addition with organocerium reagents and subsequent oxidative aromatization with chloranil. This strategy allows the generation of pyridines with various substitution patterns and introduces a variety of substituents including aryl, alkyl, alkynyl, alkenyl, and heteroaryl groups at the desired positions.

The preparation of a variety of sulfonated carbons and their use in the esterification of oleic acid is reported. All sulfonated materials show some loss in activity associated with the leaching of active sites. Exhaustive leaching shows that a finite amount of activity is lost from the carbons in the form of colloids. Fully leached catalysts show no loss in activity upon recycling. The best catalysts; 1, 3, and 6; show initial TOFs of 0.07 s(-1), 0.05 s(-1), and 0.14 s(-1), respectively. These compare favorably with literature values. Significantly, the leachate solutions obtained from catalysts 1, 3, and 6, also show excellent esterification activity. The results of TEM and catalyst poisoning experiments on the leachate solutions associate the catalytic activity of these solutions with carbon colloids. This mechanism for leaching active sites from sulfonated carbons is previously unrecognized. (C) 2013 Elsevier Ltd. All rights reserved.

Nitroxyl (HNO) has gained interest as a potential treatment of congestive heart failure through the ability of the HNO donor, Angeli's salt (AS), to evoke positive inotropic effects in canine cardiac muscle. The release of nitrite during decomposition limits the use of AS requiring other HNO sources. Acyloxy nitroso compounds liberate HNO and small amounts of nitrite upon hydrolysis and the synthesis of the water-soluble 4-nitrosotetrahydro-2H-pyran-4-yl acetate and pivalate allows for pig liver esterase (PLE)-catalysis increasing the rate of decomposition and HNO release. The pivalate derivative does not release HNO, but the addition of PLE catalyzes hydrolysis (t1/2=39min) and HNO formation (65% after 30min). In the presence of PLE, this compound converts metmyoglobin (MetMb) to iron nitrosyl Mb and oxyMb to metMb indicating that these compounds only react with heme proteins as HNO donors. The pivalate in the presence and the absence of PLE inhibits aldehyde dehydrogenase (ALDH) with IC50 values of 3.5 and 3.3μM, respectively, in a time-dependent manner. Reversibility assays reveal reversible inhibition of ALDH in the absence of PLE and partially irreversible inhibition with PLE. Liquid chromatography–mass spectrometry (LC–MS) reveals formation of a disulfide upon incubation of an ALDH peptide without PLE and a mixture of disulfide and sulfinamide in the presence of PLE. A dehydroalanine residue forms upon incubation of this peptide with excess AS. These results identify acyloxy nitroso compounds as unique HNO donors capable of thiol modification through direct electrophilic reaction or HNO release.

High-performance liquid chromatography in conjunction with electrospray mass spectrometry (LC-ESMS) was used to structurally characterize the adducts formed by the platinum-acridine agent [PtCl(en)(N-(2-(acridin-9-ylamino)ethyl)-N-methylpropionimidamide)](NO(3))(2) (compound 1) in cell-free DNA. Compound 1 forms monofunctional adducts exclusively with guanine, based on the fragments identified in enzymatic digests (dG*, dGMP*, dApG*, and dTpG*, where the asterisk denotes bound drug). The time course of accumulation and DNA adduct formation of compound 1 and the clinical drug cisplatin in NCI-H460 lung cancer cells at physiologically relevant drug concentrations (0.1 μM) was studied by inductively-coupled plasma mass spectrometry (ICP-MS). Compound 1 accumulates rapidly in cells and reaches intracellular levels of up to 60-fold higher than those determined for cisplatin. The hybrid agent shows unusually high DNA binding levels: while cisplatin adducts form at a maximum frequency of 5 adducts per 10(6) nucleotides, compound 1 produces 25 adducts per 10(6) nucleotides after only 3 h of continuous incubation with the lung cancer cells. The high overall levels of compound 1 in the cells and in cellular DNA over the entire 12-h treatment period translate into a rapid decrease in cell viability. Possible implications of these findings for the mechanism of action of compound 1 and the agent's potential to overcome tumor resistance to cisplatin are discussed.

2 1(e2Y +2 e_ e +2 e-) Isin (x + iY)1 -----e + e-w eiw + e-iw and recalling that cosh w = 2 and cos w = 2 we see that the first equation in (2) has been proved. Replacing x by (x + in) and using the fact that cosx = sin (x + in) we get the second equation in (2) immediately. MARCUS WRIGHT and THOMAS J. OSLER Mathematics Department, Rowan University, Glassboro, NJ 08028 USA e-mails: Wright@rowan.edu and Osler@rowan.edu

Substituted Internal Alkene Complex Kerry A. Pickin, Cynthia S. Day, Marcus W. Wright, and Mark E. Welker* Department of Chemistry, Wake Forest University, P.O. Box 7486, Winston-Salem, NC 27109 An unusual cobaloxime substituted terminal alkene has been isolated and characterized by X-ray crystallography. The double bond in the alkene readily isomerizes but the title compound could be isolated and structurally characterized at low temperature. Comment We have been interested in the preparation of cobaloxime complexes (cobaloxime = (pyridine)(dimethylglyoxime)2cobalt) which contain cobalt-sp 2 carbon bonds and the use of these complexes in cycloaddition chemistry (Welker, 2001). In 2000, we reported a new method for the preparation of cobalt-sp 2 carbon bonds which involved a zinc mediated coupling of alkenyl halides and triflates (II) to (pyr)2(dmg)2Co (Pickin and Welker, 2000). One of the coupling products prepared, a 2-cobaloxime substituted 1hexene (III) isomerized readily to (E)-2-cobaloxime-2-hexene (IV). The 2-cobaloxime 1hexenyl complex (III) has now been crystallized at low temperature and its structure is reported here.

Facile, two-step synthesis and kinetic characterization of new chemical probes for selective labeling of sulfenic acid (-SOH) in proteins are presented. The synthesis route relies on the simple and highly efficient Michael addition of thiol containing tags or linkers to 4-cyclopentene-1,3-dione, the unsaturated derivative of 1,3-cyclopentanedione.

S-Nitrosothiols (RSNOs) represent an important class of post-translational modifications that preserve and amplify the actions of nitric oxide and regulate enzyme activity. Several regulatory proteins are now verified targets of cellular S-nitrosation, and the direct detection of S-nitrosated residues in proteins has become essential to better understand RSNO-mediated signaling. Current RSNO detection depends on indirect assays that limit their overall specificity and reliability. Herein, we report the reaction of S-nitrosated cysteine, glutathione, and a mutated C165S alkyl hydroperoxide reductase with the water-soluble phosphine tris(4,6-dimethyl-3-sulfonatophenyl)phosphine trisodium salt hydrate (TXPTS). A combination of NMR and MS techniques reveals that these reactions produce covalent S-alkylphosphonium ion adducts (with S-P(+) connectivity), TXPTS oxide, and a TXPTS-derived aza-ylide. Mechanistically, this reaction may proceed through an S-substituted aza-ylide or the direct displacement of nitroxyl from the RSNO group. This work provides a new means for detecting and quantifying S-nitrosated species in solution and suggests that phosphines may be useful tools for understanding the complex physiological roles of S-nitrosation and its implications in cell signaling and homeostasis.