scholarly journals Kinetics and Mechanism of Nanoparticles-Catalyzed Piperidinolysis of Anionic Phenyl Salicylate

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Norazizah Abd. Razak ◽  
M. Niyaz Khan
Keyword(s):  
Rate Constants ◽  
Binding Constant ◽  
Cetyltrimethylammonium Bromide ◽  
Catalytic Effect ◽  
Binding Constants ◽  
Bulk Water ◽  
Kinetics And Mechanism ◽  
Water Phase ◽  
Phenyl Salicylate ◽  
Spherical Micelles

The values of the relative counterion (X) binding constantRXBr(=KX/KBr, whereKXandKBrrepresent cetyltrimethylammonium bromide, CTABr, micellar binding constants ofXv-(in non-spherical micelles),v=1,2, and Br−(in spherical micelles)) are 58, 68, 127, and 125 forXv−=1−, 12−, 2−, and22-, respectively. The values of 15 mM CTABr/[NavX] nanoparticles-catalyzed apparent second-order rate constants for piperidinolysis of ionized phenyl salicylate at 35°C are 0.417, 0.488, 0.926, and 0.891 M−1 s−1forNavX= Na1, Na21, Na2, and Na22, respectively. Almost entire catalytic effect of nanoparticles catalyst is due to the ability of nonreactive counterions,Xv-, to expel reactive counterions,3−, from nanoparticles to the bulk water phase.

Spectrophotometric determination of Cationic Micellar Binding Constant of Ionised Phenyl Salicylate in the presence of Inert Salts

2001 ◽  
Vol 2001 (4) ◽  
pp. 143-145 ◽  
Author(s):  
M. Niyaz Khan ◽  
Emran Ismail
Keyword(s):  
Spectrophotometric Determination ◽  
Binding Constant ◽  
Cetyltrimethylammonium Bromide ◽  
Empirical Relationship ◽  
Constant Amount ◽  
Empirical Parameter ◽  
Phenyl Salicylate ◽  
Inert Salt

A spectrophotometric technique has been used to determine the cetyltrimethylammonium bromide (CTABr) micellar binding constant ( KS) of ionised phenyl salicylate (PS-) in the presence of a constant amount of inert salt (MX = NaBr or C6H5COONa). The values of KS at different [MX] follow an empirical relationship: KS = KS0/(1 + KX/S[MX]) where the magnitude of the empirical parameter KX/S is the measure of the ability of X- to expel S- (= PS-) from the CTABr micellar pseudophase to the aqueous pseudophase. The value of KX/S is nearly 13-fold larger for C6H5COO-than for Br-.

Interaction and micellar solubilization of diclofenac with cetyltrimethylammonium bromide: A spectrophotometric study

2009 ◽  
Vol 74 (3) ◽  
pp. 503-513 ◽  
Author(s):  
Reza Hosseinzadeh ◽  
Mohammad Gheshlagi
Keyword(s):  
Partition Coefficient ◽  
Micellar Solution ◽  
Cetyltrimethylammonium Bromide ◽  
Binding Constants ◽  
Spectrophotometric Study ◽  
Bulk Water ◽  
Micellar Solubilization ◽  
Cationic Micelles ◽  
Drug Concentrations ◽  
Aqueous Micellar Solution

In this study, the interaction of diclofenac (Dic) with cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated. The effect of cationic micelles on solubilization of diclofenac in aqueous micellar solution was studied at pH 6.8, 29 °C and various drug concentrations. The binding of diclofenac to CTAB micelles was accompanied by a batochromic shift in the drug absorption spectra. The solubility of diclofenac increased with increasing surfactant concentration as a consequence of the association between the drug and micelles. From the results, the binding constants Kb, was obtained. By using the pseudo-phase model, the partition coefficient between the bulk water and CTAB micelles, Kx, and the Gibbs energy of binding were calculated. The value of binding constant and partition coefficient are increased by increasing of diclofenac concentration.

New Structure of CTAB Templated Silica Films as revealed by GISAXS coupled to HRTEM

2000 ◽  
Vol 628 ◽  
Author(s):  
Sophie Besson ◽  
Catherine Jacquiod ◽  
Thierry Gacoin ◽  
André Naudon ◽  
Christian Ricolleau ◽  
...  
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Grazing Incidence ◽  
Hexagonal Structure ◽  
X Ray Diffraction ◽  
Electronic Microscopy ◽  
Silica Films ◽  
X Ray ◽  
X Ray Scattering ◽  
Hexagonal Arrangement ◽  
Spherical Micelles

ABSTRACTA microstructural study on surfactant templated silica films is performed by coupling traditional X-Ray Diffraction (XRD) and Transmission Electronic Microscopy (TEM) to Grazing Incidence Small Angle X-Ray Scattering (GISAXS). By this method it is shown that spin-coating of silicate solutions with cationic surfactant cetyltrimethylammonium bromide (CTAB) as a templating agent provides 3D hexagonal structure (space group P63/mmc) that is no longer compatible with the often described hexagonal arrangement of tubular micelles but rather with an hexagonal arrangement of spherical micelles. The extent of the hexagonal ordering and the texture can be optimized in films by varying the composition of the solution.

scholarly journals Kinetics and mechanism of cetyltrimethylammonium bromide catalyzed oxidation of diethylene glycol by chloramine-T in acidic medium

2003 ◽  
Vol 68 (7) ◽  
pp. 535-542 ◽  
Author(s):  
V.W. Bhagwat ◽  
J. Tiwari ◽  
A. Choube ◽  
B. Pare
Keyword(s):  
Diethylene Glycol ◽  
Acidic Medium ◽  
Cetyltrimethylammonium Bromide ◽  
Reaction Rate ◽  
Chloride Ions ◽  
Kinetics And Mechanism ◽  
Product Analysis ◽  
Rate Determining Step ◽  
Chloramine T ◽  
Catalyzed Oxidation

The kinetics and mechanism of the C16TABcatalyzed oxidation of diethylene glycol (2,2?-oxydiethanol) by chloramine-T in acidic medium has been studied. The reaction has a first-order dependence on chloramine-T. With excess concentrations of other reactants, the reaction rate follows fractional order kinetics with respect to [diethylene glycol]. The micellar effect due to cetyltrimethylammonium bromide, a cationic surfactant, has been studied. The reaction is catalyzed by chloride ions as well. The small salt effect and increase in the reaction rate with increasing dielectric constant suggest the involvement of neutral molecules in the rate determining step. Addition of p-toluenesulfonamide retards the reaction rate. On the basis of product analysis, a pertinent mechanism is proposed.

scholarly journals Bifunctional intercalation and sequence specificity in the binding of quinomycin and triostin antibiotics to deoxyribonucleic acid

1978 ◽  
Vol 173 (1) ◽  
pp. 115-128 ◽  
Author(s):  
J S Lee ◽  
M J Waring
Keyword(s):  
Binding Constant ◽  
Binding Constants ◽  
Sequence Specificity ◽  
Peptide Antibiotics ◽  
Naturally Occurring ◽  
Binding Isotherms ◽  
Triostin A ◽  
Specificity Pattern ◽  
Intercalating Agents ◽  
Binding Curves

Quinomycin C, triostin A and triostin C are peptide antibiotics of the quinoxaline family, of which echinomycin (quinomycin A) is also a member. They all remove and reverse the supercoiling of closed circular duplex DNA from bacteriophage PM2 in the fashion characteristic of intercalating drugs, and the unwinding angle at I 0.01 is, in all cases, almost twice that of ethidium. Thus, as with echinomycin, they can be characterized as bifunctional intercalating agents. For the triostins this conclusion has been confirmed by measurements of changes in the viscosity of sonicated rod-like DNA fragments; the helix extension was found to be almost double that expected for a simple monofunctional intercalation process. For triostin A, further evidence for bifunctionality was derived from the cross-over point of binding isotherms to nicked circular and closed circular bacteriophage-PM2DNA. Binding curves for the interaction of quinomycin C and triostin A with a variety of synthetic and naturally occurring nucleic acids were determined by solvent-partition analysis, but triostin C was too insoluble in aqueous solution to make this method applicable. For quinomycin C the highest binding constant was found with Micrococcus lysodeikticus DNA, and its pattern of specificity among natural DNA species was broadly similar to that of echinomycin, although the binding constants were 2–6 times as large. For triostin A the highest binding constant was again found for M. lysodeikticus DNA, but the specificity pattern was quite different from that of the quinomycins. In particular, triostin A bound better to poly(dA-dT) than to the poly(dG-dC) whereas this order was reversed for quinomycin C. There was also evidence that the binding to poly(dA-dT) might be co-operative in nature. No significant interaction could be detected with poly(dA).poly(dT) or with RNA from Escherichia coli. Poly(dG).poly(dC) gave variable results, depending on the source of the polymer. The different patterns of specificity displayed by the quinomycins and triostins are tentatively ascribed to differences in their conformations in solution.

Host-guest interactions of cyclodextrins and metalloporphyrins: supramolecular building blocks toward artificial heme proteins

2004 ◽  
Vol 08 (02) ◽  
pp. 125-140 ◽  
Author(s):  
Huchen Zhou ◽  
John T. Groves
Keyword(s):  
Binding Constant ◽  
Molecular Design ◽  
Covalent Binding ◽  
Binding Constants ◽  
Building Blocks ◽  
Binding Pocket ◽  
Axial Ligand ◽  
Pyridyl Nitrogen ◽  
H Nmr ◽  
Self Assembled

Cyclodextrins are versatile building blocks for a variety of macromolecules due to the inclusion complexes that are formed with hydrophobic organic molecules. Cyclodextrin-porphyrin interactions are of particular interest since cyclodextrins can serve as a non-covalent binding pocket while metalloporphyrins could serve as the heme analogs in the construction of heme protein model compounds. Various approaches to the design and assembly of biomimetic porphyrin constructs are compared and contrasted in this minireview with a particular emphasis on self-assembled and porphyrin-cyclodextrin systems. Several recent advances from our laboratories are described in this context. A sensitive fluorescent binding probe, 6A-N-dansyl-permethylated-β-cyclodextrin (Dan-NH-TMCD), was found to form 2:1 complexes with the meso-tetraphenylporphyrins Mn(III)TCPP , Mn(III)TPPS and Mn(III)TF 4 TMAP with high binding constants. A perPEGylated cyclodextrin, heptakis(2,3,6-tri-O-2-(2-(2-methoxyethoxy)ethoxy)ethyl)-β-cyclodextrin (TPCD), has been shown by 1 H NMR spectroscopy to form a 1:1 complex with H 2 TCPP with a binding constant above 108M-1. Such a strong binding constant is the largest found for a 1:1 complex between a monomeric cyclodextrin and a guest. TPCD was also found to bind Mn(III)TCPP with a binding constant of 1.2 × 106 M -1. A novel, self-assembled hemoprotein model, hemodextrin is also described. The molecular design is based on a PEGylated cyclodextrin scaffold that bears both a heme-binding pocket and an axial ligand that binds an iron porphyrin. The binding constant for Fe (III) TPPS (iron(III) meso-tetra(4-sulfonatophenyl)porphyrin) by py-PPCD was determined to be 2 × 106 M -1. The pyridyl nitrogen of py-PPCD was shown to ligate to the iron center by observing signal changes in the Fe(II) -porphyrin 1 H NMR spectrum. This hemodextrin ensemble, a minimalist myoglobin, was shown to bind dioxygen reversibly and to form a stable ferryl species.

Binding constants for tetramethylammonium ion determined with irreversible inhibitors of acetylcholinesterase

1976 ◽  
Vol 54 (10) ◽  
pp. 918-920 ◽  
Author(s):  
F. Iverson
Keyword(s):  
Rate Constant ◽  
Binding Constant ◽  
Binding Constants ◽  
Single Site ◽  
Reversible Binding ◽  
Bimolecular Rate Constant ◽  
Irreversible Inhibitors ◽  
Carbamate Inhibitors

The reversible binding constant (Ki) for tetramethylammonium ion (TMA) was determined from the decrease in the bimolecular rate constant (ki) observed with each of 21 organophosphate or carbamate inhibitors of acetylcholinesterase (EC 3.1.1.7). The Ki values obtained were reasonably constant (5.8 × 10−4 ± 0.38 M), and this is consistent with reports indicating that TMA binds to a single site on the enzyme.

The use of β-cyclodextrins to enhance the aqueous solubility of trichloroethylene and perchloroethylene and their removal from soil organic matter: Effect of substituents

2003 ◽  
Vol 81 (1) ◽  
pp. 45-52 ◽  
Author(s):  
Salma Shirin ◽  
Erwin Buncel ◽  
Gary W vanLoon
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Binding Constant ◽  
Binding Constants ◽  
Aqueous Solubility ◽  
Solubility Enhancement ◽  
Degree Of Substitution ◽  
Water Remediation ◽  
Effective Removal ◽  
Matter Effect

This paper describes a systematic study for the evaluation of different substituted β-cyclodextrins (β-CDs), as agents for the enhancement of the aqueous solubility of two major organic pollutants, trichloroethylene (TCE) and perchloroethylene (PCE). The aqueous solubility enhancement occurs through the formation of host–guest inclusion complexes between the CD molecule (host) and the polychloroethylene (guest) and is driven primarily by hydrophobic forces. The CDs evaluated are: methyl-β-CD (Mβ-CD), hydroxypropyl-β-CD (HPβ-CD), carboxymethyl-β-CD (CMβ-CD1, CMβ-CD2), and sulfated-β-CD (Sβ-CD1, Sβ-CD2); the degree of substitution was also varied. Using a 5% (w/v) aqueous CD solution, solubility enhancement factors (St/So) up to 5.5 and 14 were determined for TCE and PCE, respectively. Binding constants (K11) for TCE with the substituted CDs were evaluated using an 1H NMR technique; these were found to range from 3 to 120 M–1. It was shown that solubility enhancement, as well as the binding constant, is dependent on the type and degree of substitution of the β-CD molecule; the determining factors are discussed. The CDs are also capable of effective removal of PCE and TCE retained by soil organic matter. Thus, a suitably substituted β-CD may be a valuable additive in pump-and-treat protocols for site remediation of polychlorinated organics. Key words: Cyclodextrin, trichloroethylene, perchloroethylene, solubility enhancement, binding constant, soil and water remediation.

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