Molecular ordering of a cyano compound at a displacive transition temperature: a statistical analysis based on quantum mechanics and computer simulations

A statistical analysis has been carried out to determine the configurational preference of a pair of 4-cyanophenyl 4-n-pentylbenzoate (CPPB) molecules with respect to translatory and orientational motions. The CNDO/2 method has been employed to evaluate the net atomic charge and atomic dipole components at each atomic centre of the molecule. Configurational energy has been computed using the Rayleigh—Schodinger perturbation method. The total interaction energy values obtained through these computations were used to calculate the probability of each configuration at the phase transition temperature using the Maxwell—Boltzmann formula. An attempt has been made to identify the most probable configuration at the phase transition temperature. Further, the flexibility of various configurations has been studied in terms of variation of probability due to small departures from the most probable configuration. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible geometrical arrangements of the molecular pair have been considered. The results are discussed in the light of experimental as well as theoretical observations. The nature of the mesophase has been correlated with the parameter introduced in this paper.     

The photocatalytic degradation of cationic surfactant from wastewater in the presence of nano-zinc oxide using Taguchi method

The photocatalytic degradation of cetyl pyridinium chloride (CPC) has been investigated in aqueous phase using ultraviolet (UV) and ZnO nanopowder. Kinetic analysis showed that the extent of surfactant photocatalytic degradation can be fitted with pseudo-first-order model and photochemical elimination of CPC could be studied by Taguchi method. Our experimental design was based on testing five factors, i.e., dosage of K₂S₂O₈, concentration of CPC, amount of ZnO, irradiation time and initial pH. Each factor was tested at four levels. The optimum parameters were found to be pH 5.0; amount of ZnO 11 mg; K₂S₂O₈ 3 mM; CPC 10 mg/L; irradiation time, 8 h.     

An Improved Method for Oxidation of Sulfides to Sulfoxides with Hydrogen Peroxide in Methanol

A variety of oxidative methods have been used for the preparation of sulfoxides from the corresponding sulfides². However, only few of them permit the oxidation in a selective manner. These methods involve for example sodium metaperiodate³, dichloroiodobenzene⁴ and t-butyl hypochlorite⁵ as oxidising agent. It should be noted that it is necessary to use them in equivalent amounts in respect to sulfide in order to avoid the over-oxidation or α-halogenation reaction.     

(S)-(−)-2-Methyl-2-Phenylsuccinic Anhydride,a Novel Resolving Reagent and its Application to Resolution of CIS-5-Amino-4-Phenyl-1,3-DIOXANE

Abstract

A new resolving reagent, (S)-(?)-2-methyl-2-phenylsuccinic anhydride (5) for the resolution of amines via covalent bond formation and its application to the resolution of aminodioxane (±)-(1) is described. The d.e. of the amides (7) and (8) has been determined by studying ¹H-NMR spectra.     

IRMPD Action Spectroscopy of Alkali Metal Cation–Cytosine Complexes: Effects of Alkali Metal Cation Size on Gas Phase Conformation

The gas-phase structures of alkali metal cation-cytosine complexes generated by electrospray ionization are probed via infrared multiple photon dissociation (IRMPD) action spectroscopy and theoretical calculations. IRMPD action spectra of five alkali metal cation–cytosine complexes exhibit both similar and distinctive spectral features over the range of ~1000–1900 cm^-1. The IRMPD spectra of the Li⁺(cytosine), Na⁺(cytosine), and K⁺(cytosine) complexes are relatively simple but exhibit changes in the shape and shifts in the positions of several bands that correlate with the size of the alkali metal cation. The IRMPD spectra of the Rb⁺(cytosine) and Cs⁺(cytosine) complexes are much richer as distinctive new IR bands are observed, and the positions of several bands continue to shift in relation to the size of the metal cation. The measured IRMPD spectra are compared to linear IR spectra of stable low-energy tautomeric conformations calculated at the B3LYP/def2-TZVPPD level of theory to identify the conformations accessed in the experiments. These comparisons suggest that the evolution in the features in the IRMPD action spectra with the size of the metal cation, and the appearance of new bands for the larger metal cations, are the result of the variations in the intensities at which these complexes can be generated and the strength of the alkali metal cation-cytosine binding interaction, not the presence of multiple tautomeric conformations. Only a single tautomeric conformation is accessed for all five alkali metal cation–cytosine complexes, where the alkali metal cation binds to the O2 and N3 atoms of the canonical amino-oxo tautomer of cytosine, M⁺(C₁).

Time Window Expansion for HDX Analysis of an Intrinsically Disordered Protein

Application of typical HDX methods to examine intrinsically disordered proteins (IDP), proteins that are natively unstructured and highly dynamic at physiological pH, is limited because of the rapid exchange of unprotected amide hydrogens with solvent. The exchange rates of these fast exchanging amides are usually faster than the shortest time scale (10 s) employed in typical automated HDX-MS experiments. Considering the functional importance of IDPs and their association with many diseases, it is valuable to develop methods that allow the study of solution dynamics of these proteins as well as the ability to probe the interaction of IDPs with their wide range of binding partners. Here, we report the application of time window expansion to the millisecond range by altering the on-exchange pH of the HDX experiment to study a well-characterized IDP; the activation domain of the nuclear receptor coactivator, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α). This method enabled mapping the regions of PGC-1α that are stabilized upon binding the ligand binding domain (LBD) of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ). We further demonstrate the method’s applicability to other binding partners of the IDP PGC-1α and pave the way for characterizing many other biologically important ID proteins.

Photopolymerization of Methyl Acrylate in Dimethyl Sulfoxide

Abstract

Methyl acrylate in dimethyl sulfoxide was polymerized by 2537 A ultraviolet light. The photo reaction exhibited zero-order kinetics for a given initial concentration and produced short chain polymers (M[Mbar]_W ～ 20,000). Low sulfur values of isolated polymers indicated no appreciable solvent incorporation during the polymerization.     

Polymer Intermediates and Polymers Derived from 5-t-Butyl-m-Xylene

Abstract

A series of condensation polymer intermediates, which included several new compositions, was prepared from 5-t-butyl-m-xylene (I) so that the effect of the bulky t-butyl group on polymer properties could be determined. Compound (I) was oxidized with nitric acid to obtain 5-t-butyl-isophthalic acid (II), which was converted successively to the diacid chloride, the diamide, the dinitrile, and finally to 5-t-butyl-m-xylene-α,α′-diamine (VI); the overall yield was 80%. The dimethyl ester of (II) was prepared and converted to 5-t-butyl-m-xylene-α,α′-diol (VIII), a new composition, in 79.5% overall yield; the diphenyl ester was also prepared. The sodium salt of (II) was catalytically reduced to obtain 5-t-butyl-1,3-cyclohexanedicarboxylic acid (IIa) in 95% yield. (IIa) was converted successively to the diacid chloride, the diamide, the dinitrile, and finally to 5-t-butyl-1,3-cyclohexanebis(methylamine) (VIa), a new composition; the overall yield was 37%. (IIa) was also converted to the dimethyl ester and finally to 5-t-butyl-1,3-cyclohexanedimethanol (VIIIa), a new composition; the overall yield was 64%. Condensation polymers were prepared from the intermediates (II), (IIa), (VI), (VIa), (VIII), and (VIIIa). These polymers had higher glass transition temperatures (T_g) than corresponding polymers containing no t-butyl groups. This general effect of the t-butyl group to increase the T_g value of the polymer was noted in all polymers prepared, regardless of whether the intermediate carrying the t-butyl group was a diacid, a diol, or a diamine, or whether the polymer was a polyamide, a polyester, or a polyurethane.     

Functional Polymers. X. Hydrolysis Studies of Polyesters and Polycarbonates of Bithionol and Their Copolymers

The hydrolysis behavior of a number of polymers of bithionol [2,2′-thiobis(4,6-dichlorphenol)] was investigated. The hydrolysis of polyesters of bithionol with aliphatic or aromatic dicarboxylic acids or phosphorus acids as well as polycarbonates and alternating copolycarbonates and polyurethanes or co(po1y-carbonates/polyurethanes) depends primarily on the water solubility of the polymer or at least on its degree of swelling. In the most favorable case of the alternating bithionol/PEG 4000 co-polycarbonate the hydrolysis rate of the polymer at 37°C was 1.62 L/mol/min at pH 10, 0.63 L/mol/min at pH 4 and 0.17 L/mol/min at pH 7.4. Copolycarbonates and copolyurethanes with PEG 4000 in the polymer chain have slightly lower rates of hydrolysis. When the solubility of the polymer is low and the crystallinity     

Synthesis of New Polyphosphazenes. The Reactions of Poly(dichlorophosphazene) with Aminotetraalkoxycyclotriphosphazene and Sodium Phenoxide

Abstract

A new poly(organophosphazenes) copolymer was formed from the reaction of aminopentafluoroethoxycyclotriphosphazene, sodium phenoxide, and poly(dichlorophosphazene). The polymer was thermoplastic and the T_g increased with an increasing amount of the phenol group. The T_g of the polymer with aminopentafluoroethoxycyclotriphosphazene attached as a pendant group was similar to the T_g of polyfluoroethoxyphosphazene.