Estimation of degree of counterion binding and thermodynamic parameters of ionic surfactants from cloud point measurements by using triblock polymer as probe

Cloud point (C(P)) was measured for ternary mixtures of different ionic surfactants such as sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB), and dimethylene bis(dodecyldimethylammonium bromide) (12-2-12) plus triblock polymer (TBP) ((PEO)(2)(PPO)(15.5)(PEO)(2)) plus water, keeping the concentration of TBP constant and varying the surfactant concentration from pre- to postmicellar regions. These experiments were also performed in the presence of different fixed amounts of NaBr to evaluate the salt effect on the clouding behavior of these ternary mixtures. The C(P) value of TBP exhibits a drastic change at the cmc of each surfactant. The cmc values thus obtained both in the absence and in the presence of NaBr were used to evaluate counterion binding (beta) with the Corrin-Harkins method. beta values were also used to evaluate the thermodynamic parameters of these ionic surfactants. The results suggest that the beta values evaluated using this method, especially at low [TBP], are in good agreement with those reported in the literature.     

Surfactant tail length-dependent lipase activity profile in cationic water-in-oil microemulsions

The catalytic activity of Chromobacterium viscosum lipase (CV-lipase) was estimated across varying surfactant tail lengths (C-10-C-18) in water-in-oil (w/o) microemulsions of cationic surfactants containing four different hydroxyethyl-substituted head groups. An attempt to find a correlation, if any, between the activity of interfacially solubilized lipase and the varying surfactant tails was made for the first time in micellar enzymology. The second-order rate constant, k2, in lipase-catalyzed hydrolysis of p-nitrophenyl-n-hexanoate at pH 6.0 and 25 degrees C shows an improvement in enzyme activity (approximately 30-140%) across different head groups of amphiphiles with increasing tail lengths in varying solution compositions. Improvement of enzyme activity is prominent in ascending from C-10 to C-14/C-16, depending on the nature of polar head group. The hydrolytic activity of lipase in different surfactant (50 mM)/water/isooctane/n-hexanol with varying z= [alcohol]/[surfactant] (6.4 or 4.8) was amplified by 25-250% with increment in surfactant tail length in comparison with widely used cationic w/o microemulsions having solution compositions (z=16). As a notable outcome of this research, we found w/o microemulsions of 25 mM tetradecyltrimethylammonium bromide/water/isooctane/n-hexanol (z=8) producing the highest ever activity of lipase in any w/o microemulsions.     

High-speed microwave-promoted hetero-Diels-Alder reactions of 2(1H)-pyrazinones in ionic liquid doped solvents

Inter- and intramolecular hetero-Diels-Alder reactions in a series of functionalized 2(1H)-pyrazinones were investigated under controlled microwave irradiation. The cycloaddition reactions were efficiently performed in sealed tubes, utilizing either a combination of 1,2-dichloroethane and a thermally stable ionic liquid, or 1,2-dichlorobenzene as reaction medium. In all cases, a significant rate-enhancement using microwave flash heating as compared to thermal heating was observed.     

Binding studies of sodium dodecyl benzene sulphonate with poly(N-vinyl-2-pyrrolidone)

The binding of sodium dodecyl benzene sulphonate (SDBS) with poly(N-vinyl-2-pyrrolidone) (PVP) has been investigated at 303.15 and 313.15 K using equilibrium dialysis, surface tension, viscosity, ultrasound velocity and ultrasound absorption techniques. From each of these studies four distinct regions of SDBS-PVP interactions were observed. Interaction of SDBS with PVP was found to involve the binding of surfactant dimers with the polymer molecule followed by usual micellization. The binding data has been analyzed in terms of various models of polymer-surfactant interaction.     

Isoperthiocyanic acid (3-amino-5-thione-l, 2, 4-dithiazole) as a new reagent for the selective detection of nitrite ion

Summary A new, simple, and selective test is described for the detection of nitrite ion with isoperthiocyanic acid (I) as the reagent. The test is based on the reaction of a 5% solution ofI with the nitrite ion solution, a deep orange precipitate being formed. Conversely, the test can be used in the identification ofI itself. Presumably, the coloured product is 3-hydroxy-5-thione-1, 2, 4-dithiazole, formed by the action of nitrous acid (producedin situ by the action of sulphuric acid and nitrite) on the 3-amino group ofI. The limit of detection is 300g of NO₂ ^– in a drop (0.05 ml). Most anions (including IO₃ ^–) do not interfere. Only I^–, thiourea, and hydrogen peroxide interfere; S₂O₃ ^2– interferes only when present in large amounts.

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Zusammenfassung Ein neuer, einfacher und selektiver Nachweis von Nitrit mit Isoperthio cyansäure (I) wurde beschrieben. Er beruht auf der Umsetzung einer 5% igen Lösung von I mit Nitritlösung, wobei ein tief orange gefärbter Niederschlag entsteht. Umgekehrt kann die Reaktion auch zum Nachweis von I dienen. Vermutlich handelt es sich bei dem gefarbten Produkt um 3-Hydroxy-5-thion-1, 2, 4-dithiazol, das durch Einwirkung der salpetrigen Säure auf die 3-Aminogruppe von I entsteht. Die Erfassungsgrenze betragt 300g NO₂ ^–im Tropfen (0,05 ml). Die meisten Anionen (inklusive JO₃ ^–) stören nicht. Nur J^–, Thioharnstoff und H₂O₂ stören; Thiosulfat stört nur in großen Mengen.

     

Organotellurium derivatives : IV. Synthesis of some diaryltellurium dihalides and pseudohalides

Iodine monohalides (ICl, IBr), cyanogen halides (CNBr, CNI) and thiocyanogen (SCN)₂ add oxidatively to diaryltellurium(II), R₂Te (R = Ph, p-Ch₃OC₆H₄) under mild conditions ( °C). The resulting organotellurium(IV) derivatives react metathetically with silver pseudohalides to yield several new diaryltellurium(IV) pseudohalide derivatives.     

Sign ambiguity in dipole moment derivatives of Br2CO

Signs of the dipole moment derivatives, ?p_x/?S₄ and ?p_x/?S₅ where p_x is the dipole moment vector along an axis perpendicular to the CO bond in the plane of the molecule and S_j are the symmetry coordinates for the B₁ vibrations of Br₂CO have been re-evaluated from the reported ?p/?Q_i values (p being the dipole moment of the molecule and Q_i the normal coordinates) and the L matrix elements. The new set of dipole moment derivatives fits well with similar parameters for Cl₂CO and F₂CO.     

Complexing behaviour ofN-phenylcarbamoylpyrrole-2-thiocarboxamide

Summary The complexes Pd(PTH)₂Cl₂ · 3.5 H₂O, Pd(PTH)₃(PPh₃), Ru(PTH)₂(PPh₃)Cl₂, Ru(PTH)₂(PPh₃)Cl₃, Rh(PTH)₂(PPh₃)Cl and Rh(PT)Cl₂ · 0.5 H₂O, where PTH isN-phenylcarbamoylpyrrole-2-thiocarboxamide, have been prepared and characterised by magnetic and spectral (i.r., u.v. and visible) studies.     

An average fock operator technique of approximate open-shell LCAO-MO-SCF calculation

The exchange part of the usual Hartree-Fock potential in the unrestricted Hartree-Fock (UHF) theory is suitablyaveraged to construct an, average one-electron model Hamiltonian which generates a set of spin-restricted one-electron orbitals in a self-consistent manner. These orbitals are then used to calculate the electronic energy of the open-shell system by using the proper functional form for the energy which handles the exchange terms correctly. The eigenvalues ofF ^av can be used for calculating either the spin-polarised or spin-averaged ionisation potentials of different orbitals at theKoopmans’ theorem level of approximation. Comparison ofE ^ac with the UHF-energy shows thatE _UHF<E ^ac in each case revealing some kind of an upper bound nature ofE ^ac. An approximate variational argument is given. Relationship of our model with the hyper-Hartree-Fock theory of slater is explored and the general problem of eliminating ‘self-interaction’ terms in average Fock-operator based theories is discussed.     

The structure,absolute configuration and biosynthesis of nortiliacorinine a

The incorporation of (±)-norcoclaurine, (±)-coclaurine, (±)-N-methylcoclaurine and dehydro-N-methylcoclaurine into nortiliacorinine A in Tiliacora racemosa colebr has been studied and specific utilisation of the (±)-coclaurine demonstrated. The evidence supports oxidative dimerization of two coclaurine units to give nortiliacorinine A. Experiments with (±)-N-methylcoclaurine and (±)-[1-³H, N-¹⁴CH₃]N-methylcoclaurine established that only one N-methylcoclaurine unit is specifically utilised to constitute that “half” of the base which had phenolic OH group in the benzylic portion and further demonstrated that the H atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion into nortiliacorinine A. Double labelling experiment with (±)-[1-³H, 6,0-¹⁴CH₃]N-methylcoclaurine showed that O-Me function of the precursor is lost in the bioconversion into nortiliacorinine A. Parallel feedings of (+)-(S)- and (-)-(R)-N-methyl-coclaurines and (-)-(S)-, and ( + )-(R)-coclaurines revealed that the stereo-specificity is maintained in the biosynthesis of nortiliacorinine A from 1-benzylisoquinoline precursors and established ‘S,S’-configuration at the two asymmetric centres in nortiliacorinine A.