NOPR Collection:

Synthesis and characterization of molecular sieves with VFI topology and their transformation to AIPO4-8

2019-03-20T06:44:45Z

Title: Synthesis and characterization of molecular sieves with VFI topology and their transformation to AIPO4-8 Authors: Prasad, S; Balakrishnan, I Abstract: Among the AIPO₄ molecular sieves, VPI-5, AIPO₄-Hl and AIPO₄-8, which possess extra-large pores in their structures, have evoked considerable interest recently. This interest is essentially centered around their structural identities regarding which there have been conflicting reports. The present work reports the results of a reinvestigation which indicate that AIPO₄-Hl and VPI-5 represent identical phases, both of which transform to AIPO₄-8 on thermal treatment. Page(s): 737-741

Substituted AIPO4-11 molecular sieves-SAPO-11 and CoAPO-11: Synthesis, acidity and alkylation 'of toluene with methanol

2019-03-20T06:41:59Z

Title: Substituted AIPO4-11 molecular sieves-SAPO-11 and CoAPO-11: Synthesis, acidity and alkylation 'of toluene with methanol Authors: Das, J; Lohokare, S P; Chakrabarty, D K Abstract: AIPO₄-11 as well as substituted SAPO-11 and CoAPO-11 have been synthesized hydrothermally in the pure state. Results of acidity measurement show that the acid strength depends on the substituent. This is also supported by the results of alkylation of toluene with methanol on these catalysts. These molecular sieves exhibit very high para selectively because of the elliptical 10-membered oxygen ring chennals. Page(s): 742-746

Base catalysed hydrolysis of β2-cis-(chloro)(benzimidazole)(trienthylenetetramine)cobalt(III)cation: A comparison of the reactivities of the benzimidazole and benzimidazolato species of the complex

2019-03-20T06:40:46Z

Title: Base catalysed hydrolysis of β2-cis-(chloro)(benzimidazole)(trienthylenetetramine)cobalt(III)cation: A comparison of the reactivities of the benzimidazole and benzimidazolato species of the complex Authors: Dash, Anadi C; Nanda, Rabindra K; Acharya, Achyuta N Abstract: The base hydrolysis of β₂-cis-(chloro)(benzimidazole)(triethylenetetramine)cobalt(III) obeys the rate law: -dln[complex]_total/dt=(k [OH^-] + k k_OH[OH^-]²)/(1 + K_OH[OH^-]) in the range of pH = 7.40-12, for which k, k and K_OH denote the second order rate constants of the benzimidazole, benzimidazolato form of the complex, and the equilibrium constant for the OH^- promoted formation of the benzimidazolato species from the parent complex respectively. At 25°C and 1= 0.05 mol dm^-3, k = (4.79±0.15) x 10⁶ dm³ mol^-1 S^-1, k = (9.2±0.6) x 10⁴ dm³ mol^-1 S^-1and KOH = (2.64 ± 0.07) x 10⁵ dm³ mol^-1. At [OH^-] = (2.6-11.6) x 10^-3 mol dm^-3 (l = 1.0 mol dm^-3) and 10-30°C, k_obs,= k [OH^-] is valid with k (25°C) = (4.42 ± 0.04) x 10⁴ dm³ mol^-1 S^-1, H^≠ = 67.6 ± 1.0 kJ mol^-1 and S^≠ = 71 ± 3 JK^-1 mol^-1. There is no general base catalysis discounting the possibility of the rate limiting NH-deprotonation mechanism. Comparison of the rate data shows that the benzimidazole form of the complex ((trien)Co(bzmH)Cl²⁺) base hydrolyses ~ 40 times faster than its benzimidazolato analogue despite the fact that the conjugate base of the latter (net charge zero) is likely to be more reactive than the same derived from the former (net charge + 1). This reactivity trend (i.e. k > k) reflects the perturbation of the pK of the NH proton of the coordinated trien forming the reactive conjugate base. In the conventional SN₁CB mechanism the reactive conjugate base is believed to be generated by the deprotonation of the planar secondary N - H of the trien ligand trans to the coordinated benzimidazole or its conjugate base (bzm). Page(s): 747-751

Kinetics of oxidation of diglycine by bromamine- B in perchloric acid Medium

2019-03-20T06:29:29Z

Title: Kinetics of oxidation of diglycine by bromamine- B in perchloric acid Medium Authors: Iyengar, T Asha; Mahadevappa, D S Abstract: Kinetics of oxidation of a typical dipeptide glycylglycine(GG) by bromamine-B (BAB) has been studied perchloric acid medium at 40°C. The rate shows first order dependence in [BAB])₀ and fractional order in [GG]₀ which tends to zero order when [H⁺] = 0.04 mol dm^-3. The reaction is almost independent of [H⁺] (when [H⁺] < 0.03 mol dm^-3) and inverse fractional in [H⁺]([H⁺] = 0.03-0.08 mol dm^-3). Other effects, like addition of halide ions, benzenesulphonamide, and variation in ionic strength and die-lectric constant of medium have also been studied. A solvent isotope effect, k’/ k’ = 1.52 is observed. Proton-inventory studies in - mixtures have been made. The reaction has been studied at different temperatures and a mechanism conforming to the kinetic observations is suggested. Page(s): 752-755