Neutral Salt (neutral + salt)

Distribution by Scientific Domains


Selected Abstracts


Mannich-Type Reactions Catalyzed by Neutral Salts in Water

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11 2003
Catherine Loncaric
Abstract Mannich-type reactions of imines with silicon enolates were found to be catalyzed by neutral salts such as sodium triflate in water as a suspension medium. Unusual kinetic behavior indicates that the presence of the Mannich adduct facilitates the rate of its formation. [source]


Mannich-Type Reactions Catalyzed by Neutral Salts in Water.

CHEMINFORM, Issue 11 2004
Catherine Loncaric
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Cation exchange in forest soils: the need for a new perspective

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2008
D. S. Ross
Summary The long-term sustainability of forest soils may be affected by the retention of exchangeable nutrient cations such as Ca2+ and the availability of potentially toxic cations such as Al3+. Many of our current concepts of cation exchange and base cation saturation are largely unchanged since the beginnings of soil chemistry over a century ago. Many of the same methods are still in use even though they were developed in a period when exchangeable aluminium (Al) and variable charge were not generally recognized. These concepts and methods are not easily applicable to acid, highly organic forest soils. The source of charge in these soils is primarily derived from organic matter (OM) but the retention of cations, especially Al species, cannot be described by simple exchange phenomena. In this review, we trace the development of modern cation exchange definitions and procedures, and focus on how these are challenged by recent research on the behaviour of acid forest soils. Although the effective cation exchange capacity (CECe) in an individual forest soil sample can be easily shown to vary with the addition of strong base or acid, it is difficult to find a pH effect in a population of different acid forest soil samples. In the very acidic pH range below ca 4.5, soils will generally have smaller concentrations of adsorbed Al3+. This can be ascribed to a reduced availability of weatherable Al-containing minerals and a large amount of weak, organic acidity. Base cation saturation calculations in this pH range do not provide a useful metric and, in fact, pH is modelled better if Al3+ is considered to be a base cation. Measurement of exchangeable Al3+ with a neutral salt represents an ill-defined but repeatable portion of organically complexed Al, affected by the pH of the extractant. Cation exchange in these soils can be modelled if assumptions are made as to the proportion of individual cations that are non-specifically bound by soil OM. Future research should recognize these challenges and focus on redefining our concepts of cation retention in these important soils. [source]


Physiological Responses of Krishum (Iris lactea Pall. var. chinensis Koidz) to Neutral and Alkaline Salts

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2008
Y. Wang
Abstract The aims of this study were to compare the physiological responses of krishum (Iris lactea Pall. var. chinensis Koidz) to neutral and alkaline salt stress and identify and examine the mechanisms involved in plant response to salt treatments. In this study, biomass, ion accumulation (Na+, K+, Ca2+, Mg2+), organic solute (proline) concentration, rate of membrane electrolyte leakage (REL) and antioxidase activities including those of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6) and peroxidase (POD, EC 1.11.1.7) were investigated in krishum under different concentrations of NaCl, Na2CO3 and the mixture of the two salts in the same volume. All three treatments caused increases in Na+ concentration, proline content and REL and decreases in root Mg2+ and K+ content. Increased Ca2+ and antioxidase activities were observed at lower external Na+ concentrations. However, at higher external Na+ levels, decreased Ca2+ and antioxidase activities were detected. Alkaline salt resulted in more damage to krishum than neutral salt including lower SOD, POD and CAT activities and decreased proline content, relative to neutral salt. High Na+ and low K+ in krishum intensified ion toxicity under alkaline condition. Alkaline salt caused greater harm to plants than neutral salt, the primary reason of which might be the lower Ca2+ content in the plant under alkaline salt stress. [source]


Cluster ions of diquat and paraquat in electrospray ionization mass spectra and their collision-induced dissociation spectra

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 12 2003
Boris L. Milman
Cluster ions such as [Cat+X+nM]+ (n,=,0,4); [Cat-H+nM]+ (n,=,1,3); and [2(Cat-H)+X+nM]+ (n,=,0,2), where Cat, X, and M are the dication, anion, and neutral salt (CatX2), respectively, are observed in electrospray ionization (ESI) mass spectrometry of relatively concentrated solutions of diquat and paraquat. Collision-induced dissociation (CID) reactions of the clusters were observed by tandem mass spectrometry (MS/MS), including deprotonation to form [Cat-H]+, one-electron reduction of the dication to form Cat+., demethylation of the paraquat cation to form [Cat-CH3]+, and loss of neutral salt to produce smaller clusters. The difference in acidity and reduction power between diquat and paraquat, evaluated by thermodynamical estimates, can rationalize the different fractional yields of even-electron ([Cat-H]+ and its clusters) and odd-electron (mostly Cat+.) ions in ESI mass spectra of these pesticides. The [Cat+n,,Solv]2+ doubly charged cluster ions, where n,,,2 and Solv is the solvent molecule (methanol and/or water), are only observed as very weak peaks in precursor ion CID spectra of the Cat2+ salt cation at low collision energy. The presence of an anion and a solvent molecule in a cluster is assumed to be related to existence of tight and loose ion pairs, respectively, in multiply charged droplets/ions formed by ESI. The results emphasize again the role of solution chemistry concepts such as acidity/basicity, redox power, and ion-pair formation, for ESI. Copyright 2003 John Wiley & Sons, Ltd. [source]


Mannich-Type Reactions Catalyzed by Neutral Salts in Water

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11 2003
Catherine Loncaric
Abstract Mannich-type reactions of imines with silicon enolates were found to be catalyzed by neutral salts such as sodium triflate in water as a suspension medium. Unusual kinetic behavior indicates that the presence of the Mannich adduct facilitates the rate of its formation. [source]


Mechanism of lidocaine release from carbomer,lidocaine hydrogels

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2002
Alvaro Jimenez-Kairuz
Abstract Rheology, acid-base behavior, and kinetics of lidocaine release of carbomer,lidocaine (CL) hydrogels are reported. A series of (CL)x (x,=,mol% of L,=,25, 50, 75, 100) that covers a pH range between 5.33 and 7.96 was used. Concentrations of ion pair ([R-COO,LH+]) and free species (L) and (LH+) were determined by the selective extraction of (L) with cyclohexane (CH) together with pH measurements, i.e., CH in a ratio CH/hydrogel 2:1 extracted 48% of the whole concentration of lidocaine [LT] of a (CL)100, {[LT],=,([R-COO,LH+]),+,(L),+,(LH+)}. The remaining species in the aqueous phase were distributed as: (L) 3.82%, (LH+) 14.5%, and [R-COO, LH+] 81.7%. Rheology and pH as a function of (CL) concentration are also reported. Delivery rates of free base L were measured in a Franz-type bicompartmental device using water and NaCl 0.9% solution as receptor media. (CL) hydrogels behave as a reservoir that releases the drug at a slow rate. pH effects on rate suggest that, under the main conditions assayed, dissociation of [R-COO,LH+] is the slow step that controls releasing rates. Accordingly, release rate was increased upon addition of a second counterion (i.e., Na+), or through the diffusion of neutral salts such as NaCl, into the matrix of the gel. 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:267,272, 2002 [source]