Effects Of Different Functional Groups Research Articles

Experimental correlation between the p Ka value of sulfonphthaleins with the nature of the substituents groups

This work presents the results obtained from a spectrophotometry study performed on some indicators of the sulfonphtaleins like phenol red (PR), thymol blue (TB), bromothymol blue (BTB), xylenol orange (XO) and methylthymol blue (MTB). During the first stage the acidity constants of some of the indicators were determined using the data from spectrophotometry, potentiometry and with the use of the software SQUAD. These were as follows: for the equilibrium 2H + BTB ↔ H 2BTB, log β 2 = 15.069 ± 0.046 and for H + BTB ↔ HBTB, log β 1 = 8.311 ± 0.044. For the XO and the MTB five values were calculated for each, namely, for MTB: log β 5 = 42.035, log β 4 = 38.567 ± 0.058, log β 3 = 32.257 ± 0.057, log β 2 = 23.785 ± 0.057, and log β 1 = 12.974 ± 0.045 while for XO: log β 5 = 40.120 ± 0.102, log β 4 = 35.158 ± 0.062, log β 3 = 29.102 ± 0.053, log β 2 = 21.237 ± 0.044, and log β 1 = 11.682 ± 0.044. During the second stage, a study was conducted on the effect of the substituents present in the indicators to determine the effect of different functional groups on the p K a value corresponding to the last indicator's dissociation.

Comonomer effects on binding performances and morphology of acrylate-based imprinted polymers

The objective of this study was to investigate the effect of different functional groups of molecularly imprinted polymers (MIPs) on the binding characteristics towards a specific template molecule by examining selectivity and recognition processes. Several non-covalent theophylline imprinted polymers (TIPs) were prepared by using only methacrylic acid (MAA), or MAA and 2-hydroxyethyl methacrylate (HEMA) comonomer, or MAA and acrylamide (ACM) comonomer. In all cases, a high amount of ethylene glycol dimethacrylate (EDMA) as crosslinker existed in the medium. The highest selective theophylline binding of TIPs was found to be 61%, 41% and 40% for MAA/EDMA, MAA/HEMA/EDMA and MAA/ACM/EDMA systems, respectively. The use of a comonomer (ACM or HEMA) reduced the binding performance of the MAA/EDMA polymer matrix, probably due to the monomer–monomer association and morphological differences. Results obtained from the batch binding experiments demonstrated that all of the TIPs have sites that have selective binding ability for theophylline, but not to another structurally similar molecule, caffeine. According to the Langmuir isotherm model, a heterogeneous distribution of binding sites was observed in the polymers. The maximum association constant and binding site density were computed as 2.3 × 10 2 mM −1 and 8.6 μmol/g, respectively, for copolymer of MAA/EDMA under the examined concentration range.

Slow-binding inhibitors of prolyl oligopeptidase with different functional groups at the P1 site.

POP (prolyl oligopeptidase) specifically hydrolyses a number of small proline-containing peptides at the carboxy end of the proline residue and POP inhibitors have been shown to have cognition-enhancing properties. It has been noted that certain functional groups at the P1 site of the inhibitor, which correspond to the substrate residue on the N-terminal side of the bond to be cleaved, increase the inhibitory potency. However, detailed mechanistic and kinetic analysis of the inhibition has not been studied. In the present study, we examined the effect of different functional groups at the P1 site of the parent inhibitor isophthalic acid bis-(L-prolylpyrrolidine) amide on the binding kinetics to POP. Addition of CHO, CN or COCH(2)OH groups to the P1 site increased the inhibitory potency by two orders of magnitude (K(i)=11.8-0.1 nM) and caused a clear slow-binding inhibition. The inhibitor containing a CHO group had the lowest association rate constant, k(on)=(2.43+/-0.12) x 10(5) M(-1) x s(-1), whereas the inhibitor with a CN group exhibited the fastest binding, k(on)=(12.0+/-0.08)x10(5) M(-1) x s(-1). In addition, the dissociation rate was found to be crucially dependent on the type of the functional group. Compounds with COCH(2)OH and CHO groups had much longer half-lives of dissociation (over 5 h) compared with the compound with the CN group (25 min), although the K(i) values of the compounds were relatively similar. A possibility to optimize the duration of inhibition by changing the functional group at the P1 site is important when planning therapeutically useful POP inhibitors.

Synthetic paths towards scalaranes: Assembling the scalaranic skeleton and further transformations

The family of scalaranic sesterterpenoids has been known since the early 70s, but they have attracted the attention of synthetic organic chemists only in the last decade. These marine natural products are considered secondary metabolites of marine organisms and have shown promising biological properties. Synthetic approaches towards scalaranes are discussed in the present review. Scalaranes are quite complex compounds, with many chiral centers and their transformations are strongly directed by steric effects of different functional groups attached to the tetracyclic framework. Therefore, methods of assembling the scalaranic skeleton are examined first, followed by the synthesis of natural products or their analogues on the basis of the available tetracyclic template.

Active testing of ruthenium porphyrins as mimic of enzyme

Three ruthenium(Ⅱ) porphyrin complexes [Ru Ⅱ(4-Cl-TPP)(CO)](1),[Ru Ⅱ(4-MeO-TPP)(CO)](2), [Ru Ⅱ(3,4,5-MeO-TPP)(CO)](3) and three ruthenium(Ⅵ) porphyrin complexes[Ru Ⅵ(4-Cl-TPP)(O) 2](4), [Ru Ⅵ(4-MeO-TPP)(O) 2 ](5),[Ru Ⅵ(3,4,5-MeO-TPP)(O) 2](6) were synthesized and their biological activities as bifunctional mimic of superoxide dismutase (SOD) and catalase (CAT) were tested. Their catalytic effects on depleting O -· 2 and decomposing H 2O 2 have been measured by riboflavin-methionine photoreduction method and spectrophotometry method respectively. The antioxidative activities of them were also studied, and the results showed these porphyrin complexes can indeed restraint the lipid peroxidation. The possible mechanism of ruthenium porphyrins catalyzing dismutation of superoxide radical and decomposition of hydrogen peroxide was put forward. In addition, the catalytic effects of different functional groups on the porphyrin rings were discussed.

Synthesis and characterization of end-capped polyimides and their gas permeability properties

Polyimides (PIs) based on 3,3′,4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-oxydianiline (ODA) end capped with two new monoamines and other four different monoamines have been synthesized with a view to study the effect of different functional groups at the end of polymer chain on solubility, gas permeability, and thermal properties. The new monoamines have been synthesized from 3-pentadecylphenol, obtained by hydrogenation of cardanol, a major constituent of cashew-nut shell liquid. Introduction of different functional groups at the end of polyimide (PI) based on ODPA and ODA, by end capping with different monoamines, alters oxygen and nitrogen gas permeability, solubility, and thermal properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 627–635, 2000

Enzymatic synthesis of multi-component copolymers and their structural characterization.

The use of enzymes in synthetic applications has increased dramatically in the recent years and the field of polymer science is part of this trend. Synthesis of a variety of polymers using lipase catalyzed (Candida antarctica) polymerization reactions has led to a variety of new materials with interesting properties in our laboratories. This paper describes the synthesis of multi-component polyesters and mixed polymers having polyester and polyamide linkages under solvent-less conditions using Candida antarctica lipase B. The effect of a third component, i.e. a series of 1,omega-alkanediols (1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol and 1,16-hexadecanediol) on the copolymerization reaction of dimethyl 5-hydroxyisophthalate with poly(ethylene glycol 600) has been studied and the mechanism for the incorporation of the third component is proposed. We have also studied the effect of different functional groups during terpolymerization reaction of dimethyl 5-hydroxyisophthalate with poly(ethylene glycol) by adding a third component having different functionalities (1,6-hexanediol, 1,6-hexanediamine or 1,6-hexanedithiol) and compared the effect of hydroxyl, amine and thiol groups on the polymerization reactions.

Crystal Design of Calcium Carbonate Microparticles Using Double-Hydrophilic Block Copolymers

Small block copolymers, consisting of a hydrophilic poly(ethylene glycol) block and a second hydrophilic moiety which strongly interacts with alkaline earth ions, were employed to template the precipitation of calcium carbonate from aqueous solution. Depending on the type of polymeric functionalization pattern used, it was possible to grow two of the three different crystal modifications of CaCO3 (vaterite and calcite) under similar conditions. Vaterite could be successfully stabilized for more than 1 year by the polymer under conditions where it would normally transform into calcite within 80 h. Also the crystal size and shape respond to the polymeric template; for example, it was possible to grow monodisperse spherical particles with a diameter of ca. 2 μm or hollow spheres both consisting of aggregated nanocrystallites. The effect of different functional groups and of variable block length on the size, shape, and morphology of CaCO3 is discussed. It must be emphasized that these particles sediment, but...

The effect of different functional groups on the ligand-promoted dissolution of NiO and other oxide minerals

Sets of homologous ligands were used to probe the dissolution of oxide minerals through experiments on bunsenite (NiO). The ligand sets have primary amine, hydroxyl, and carboxyl functional groups and form five-membered, bidentate, ring complexes at the mineral surface. A set of ligands that has only two metal-coordinating functional groups ( ox, en, gly) was compared with a set of larger, but similar, ligands ( nta, tren) that link three sets of functional groups with a tertiary amine. Experiments were also conducted with hydroxyl ligands ( tea), ammonia (NH 3), and ligands containing ring nitrogen ( pic). The dissolution rates of NiO(s) in the presence of these ligands established close consistency between metal detachment from a dissolving surface and the mechanisms of ligand exchange around dissolved Ni(II)-ligand complexes. The solution pH, however, is an important complicating factor. Metals compete with protons for ligand sites and this protonation changes the ligand structure and reactivity. Several types of protonation lead to different species at the mineral surface and this greatly complicates the rate laws for dissolution. The speciation will be particularly complicated for large-molecular-weight ligands with functional groups that protonate over a wide pH range. In terms of a rate law, protonation of ligand functional groups at the surface is distinct from protonation of structural oxygens at the mineral surface. These are different surface complexes (species) for the purpose of the rate law.

Amphiphilic dyes for nonlinear optics: Dependence of second harmonic generation on functional group substitution

Communication: Orientation of chromophores by using the Langmuir‐Blodgett film‐prepration procedure, to a degree practically impossible to achieve by poling in polymer matrices in an electric field, has held to materials exhibiting the highest values of the second order susceptibility (χ(2)) yet known. The effect of different functional groups in both phenylhydrazone and stryrylpyridinium compounds on both molecular nonlinearity and order in the films the factors which most strongly influence (χ(2)) has been investigated and a thioether substituent is found to increas (χ(2)) significantly.

MNDO calculations on tetrathiafulvalenes

The effects of different functional groups on tetrathiafulvalenes (TTF) are examined by semi-empirical MNDO calculations. The calculated ionization potentials correlate reasonably well with experimental oxidation potentials measured in solution. The shape of the highest occupied molecular orbital is insensitive to the nature of the substituents, although the calculated ionization potentials differ by up to 2 eV. The relaxation energy upon formation of the radical cation, defined as the difference between vertical and adiabatical ionization potentials, is calculated to be 0.09 – 0.26 eV, depending on the substituents. Extending the conjugation of the TTF molecule by additional vinylenedithia units makes the systems progressively poorer electron donors and the effects of functional groups are less than for TTF itself.

Functional group efficiency in adhesion between polyethylene and aluminum

AbstractThe effect of different functional groups on the adhesion between polyethylene and aluminum has been studied. Poly(ethylene‐co‐butyl acrylate) (EBA) and poly(ethylene‐co‐vinyl acetate) (EVA) were used as such and provided polyethylene surfaces with two different kinds of ester groups, butyl ester and acetate, respectively. By alkaline hydrolysis in an organic solvent the surface functionality could be changed to carboxylate and hydroxyl, respectively. Finally, acid washing converted the carboxylate groups into carboxylic acid. The effect of the surface treatments were followed by reflection IR. T‐peel tests of laminates made of the original, as well as the surface‐treated polymers, and aluminum allowed an evaluation of the specific contribution to the adhesion for the groups in question. The peel strength increased linearily with the bulk concentration of comonomer in the original EBA and EVA samples. The values increased from about 100 N/m for polyethylene up to 2500 N/m in the case of 3.7 mol % of carboxylic acid. The efficiency of the investigated functional groups increased in the following order: H<OCOCH3 <COOC4H9 <COONa∼OH<COOH.

High-performance liquid chromatographic elution behaviour of alcohols, aldehydes, ketones, organic acids and carbohydrates on a strong cation-exchange stationary phase

The high-performance liquid chromatographic separation of alcohols, aldehydes, ketones, carboxylic acids and carbohydrates on a polystyrene-based strong cation-exchange resin is described. The column temperature was found to be a very important parameter for optimizing separations of these substances. The effect of different functional groups on the elution behaviour is discussed.

Investigation of a microwave plasma emission spectrometer as a quantitative detector for glass capillary gas chromatography

The properties of various detectors for quantitative gas chromatographic analysis are briefly reviewed. Two equations formulated for calculating quantitative results obtained by microwave plasma emission spectrometry (MES) were applied in this study. The validity of this calculation method without calibration has been examined by employing seven known mixtures consisting of hetero-atomic organic compounds. Matrix effects of different functional groups and hetero-atoms of organic compounds on MES and flame ionization detector (FID) responses were investigated, and an approximately linear relationship between the peak area of each component determined by MES and the elemental content of the respective component was found. FID responses were significantly affected by the hetero-atomic compounds.