4-Aminophthalimide Derivatives as Environment-Sensitive Probes

The potential of 4-aminophthalimide (AP) and its derivatives as fluorescence probes for organized media is highlighted. The fluorescence response of AP, as measured from the position of the fluorescence maximum, fluorescence intensity and lifetime, is highly sensitive to the polarity of the medium. The sensitivity of the fluorescence parameters is further enhanced due to the involvement of the emitting intramolecular charge transfer state in hydrogen bonding interaction with the solvent molecules containing hydroxyl groups. It is shown that the microheterogeneous environments of organized media such as cyclodextrins and micelles can be very conveniently monitored using this probe. The results of the investigations carried out employing AP and its derivatives as fluorescence probe molecules in these media clearly suggest that a combination of the hydrophobic interaction with the host media and hydrogen bonding interaction with the solvent molecules determine the location of the fluorophore, which in all cases is found to be the interfacial region separating the nonpolar core of the micelle or the cyclodextrin cavity and the polar aqueous environment. Guidelines for the design of probes of this class of systems for the nonpolar core region of the micelles are provided and possible ways to increase the sensitivity of the fluorescence response of the systems are suggested.     

Vapor phase acylation of phenol over Hβ, CeHβ and SO42-/ZrO2a

Phenol acylation on Hβ, CeHβ and SO₄ ^2-/ZrO₂ using acetic acid and acetic anhydride as acylating agents is compared in the temperature range 250-400°C. Acetic acid formed phenyl acetate (PA) and o-hydroxy acetophenone (o-HAP) and acetic anhydride formed p-hydroxyacetophenone (p-HAP ) along with PA and o-HAP. The formation of o-HAP and p-HAP, the products of C-acylation of phenol using acetic acid is proposed by studying phenyl acetate conversion on Hb, CeHβ and SO₄ ^2-/ZrO₂. Our studies show that for phenol acylation the most suitable acid site is available on CeHβ. This revised version was published online in June 2006 with corrections to the Cover Date.     

Kinetics and mechanism of electron transfer reactions involving pyridinium chlorochromate and α-hydroxy acids in acid medium catalysed by ruthenium(III)

Summary The oxidation of -hydroxy acids (HA), viz. glycolic acid (GA), mandelic acid (MA) and lactic acid (LA), by pyridinium chlorochromate (PCC) in aqueous ethanoic acid solution was investigated in the presence and absence of Ru^IIICl₃. The order in [HA] and [PCC] was found to be unity, with or without ruthenium(III) catalyst, and the order in [Ru^III] was found also to be unity. The reaction was acid catalysed also in the presence and absence of ruthenium(III) catalyst, and hence the protonated form of PCC, was assumed to be the active species of oxidant. Added salts, and the change in dielectric constant of the medium, did not affect the oxidation rate. No induced polymerization occurred when acrylamide monomer was added to the reaction mixture. The pseudo-first order rate constants (k the formation constants (K _f) of the substrate-catalyst complexes, activation and thermodynamic parameters have been evaluated. Suitable mechanisms in conformity with the experimental observations have been proposed for the uncatalysed and catalysed reactions.     

Photophysical behaviour of some pyrenylethylene derivatives and its implication on trans → cis photoisomerisation reactions

The fluorescence properties of some pyrenylethylene derivatives capable of exhibiting twisted intramolecular charge transfer phenomenon havebeen studied as a function of solvent polarity. The solvent polarity dependent change in the fluorescence quantum yield has been interpreted in terms of intramolecular retational relaxations. The trans → cis photoisomerization data of the compounds indicate that the twist around the ethylenic double bond is accelerated in polar solvents.     

Ruthenium(III), osmium(VIII) and ruthenium(III) + osmium(VIII) catalysed oxidations ofi-propanol by N-bromosuccinimide in basic solution

Summary The oxidation ofi-propanol (IPA) by N-bromosuccinimide (NBS) in basic solution was investigated separately in the presence of Ru^III, Os^VIII and Ru^III + Os^VIII ions. The order in [IPA] was found to be 0.7, 0.5 and 0.3 respectively in the above three cases in the concentration range studied. The order in [NBS] was unity in the presence of Ru^III chloride but was found to be zero in the case of Os^VIII and Ru^III+Os^VIII catalysis. The order in [metalion] was found to be nearly unity in all the three catalysed reactions. Increase in [^–OH] increased the rate of reaction while addition of succinimide retarded the rate of reaction. Decrease in dielectric constantsof the medium decreased the rate of oxidation. The pseudo first order rate constants (k), zero order rate constants (k₀) and the formation constants (k_f) of the substrate-catalyst complexes and the thermodynamic parameters have been evaluated. Suitable mechanisms in conformity with the experimental observations have been proposed for the three catalysed reactions.     

A new subclass of meromorphic functions with positive coefficients

In the present paper, we consider the new subclass of Meromorphic functions with positive coefficients and obtain a necessary and sufficient condition for a function f to be in this class. We obtain distortion properties, radius of convexity, starlikeness, convex linear combinations for the function f in this class.     

A Convenient Method of Esterification of Fatty Acids. Preparation of Alkyl Esters,Sterol Esters,Wax Esters and Triacylglycerols

A quick and mild, one-pot method of esterification of fatty acids with primary, secondary and tertiary alcohols as well as with fatty alcohols, sterols and glycerol is proposed via the acyl bromides formed in situ.     

Impact of season and location on the natural radioactivity in marine macroalgae (<Emphasis Type="Italic">Gracilaria edulis)</Emphasis> of coastal Tamil Nadu,India

Gracilaria edulis, an edible red marine macro algae from three high background radiation areas (Arockiapuram, Kadiapattinam and Kurumpanai) on the southwest coast of Tamil Nadu, and one low background radiation area (Mandapam) on the southeast coast of Tamil Nadu, in India, were studied for variations in average gross alpha and beta radiation activities. Significant variations in average gross beta activities were observed while alpha activities showed only marginal variation. The average gross alpha activity was recorded high (61.51 Bq kg ⁻¹) during the post southwest monsoon season, while it recorded lowest (25.48 Bq kg ⁻¹) during the post northeast monsoon season. Average gross beta activity varied between seasons with the lowest level (211.55 Bq Kg⁻¹) during post southwest monsoon season and the highest (413.33 Bq kg ⁻¹) during post northeast monsoon season. Among the four locations, the gross alpha activity was high (70.95 ± 26.74 Bq Kg⁻¹) in Arockiapuram and low (18.74 ± 6.32 Bq Kg⁻¹) in Mandapam, while the gross beta activity was high (442.25 ± 168.53 Bq Kg⁻¹) in Kurumpanai and low (158.63 ± 34.37 Bq Kg⁻¹) in Mandapam. Average gross alpha activity in G. edulis was found significantly varying in terms of locations, while average gross beta activity for the same species recorded significant seasonal variation.     

Kinetics of polymerization of 1-octene with Mgcl2-supported Ticl4 catalysts

A number of TiCl₄ catalysts supported on MgCl₂ which was activated by the recrystallization method using different alcohols were prepared with ethyl benzoate or dibutyl phthalate as the internal electron donor. All the catalysts were characterized by BET, x-ray diffraction, and hydrolysis–GC analysis. Kinetics of polymerization of 1-octene was studied with three of the above catalysts (having different internal electron donors) activated by AlEt₃. The rate of polymerization increased linearly with increasing temperature, and catalyst and monomer concentrations. From the Arrhenius plot, the overall activation energies of polymerization were determined and the dependence of rate on the AlEt₃ concentration could be explained by the Langmuir-Hinshelwood mechanism. ¹³C-NMR was used to study the effect of internal electron donors on the % isotacticity of poly(1-octene). The catalytic activities of all the catalysts were compared in 1-octene polymerization. © 1994 John Wiley & Sons, Inc.     

High temperature drop calorimetry measurements of enthalpy increment in Ti–xTa (x=5, 10, 15, 20 mass%) alloys

The enthalpy increment for a series of Ti–xTa (x=5, 10, 15, 20 mass%) alloys, having α(hcp)+β(bcc) two phase microstructure has been measured using inverse drop calorimetry in the temperature range 463–1257 K. The studies clearly revealed the occurrence of α→β diffusional phase transformation. Both the α→β transformation onset temperatures and the measured transformation enthalpy Δ⁰H_tr^α→β exhibit progressively lower values with increasing Ta content. It is found that the measured enthalpy in the transformation region is constituted of two principal contributions namely, (i) the enthalpy due to untransformed α and coexisting β phases and (ii) the transformation enthalpy due to α→β phase change. Since the fractional extent of α→β transformation varies continuously with temperature, the measured enthalpy variation in the transformation domain has been modeled using Kolmogorov–Johnson–Mehl–Avrami formalism for the diffusional transformation kinetics. The thermodynamic quantities for all the alloys have been derived.