Kinetics of Lab Prepared Manganese Oxide Catalyzed Oxidation of Benzyl Alcohol in the Liquid Phase

The oxidation of benzyl alcohol in the liquid phase was studied over manganese oxide catalyst using molecular oxygen as an oxidant. Manganese oxide was prepared by a mechanochemical process in solid state and was characterized by chemical and physical techniques. The catalytic performance of manganese oxide was explored by carrying out the oxidation of benzyl alcohol at 323–373 K temperature and 34–101 kPa partial pressure of oxygen. Benzaldehyde and benzoic acid were identified as the reaction products. Typical batch reactor kinetic data were obtained and fitted to the Langmuir–Hinshelwood, Eley–Rideal, and Mars–van Krevelene models of heterogeneously catalyzed reactions. The Langmuir–Hinshelwood model was found to give a better fit. Adsorption of benzyl alcohol at the surface of the catalyst followed the Langmuir adsorption isotherm. The heat of adsorption for benzyl alcohol was determined as –18.14 kJ mol^?1. The adsorption of oxygen followed the Temkin adsorption isotherm. The maximum heat of adsorption for oxygen was –31.12 kJ mol^?1. The value of activation energy was 71.18 kJ mol^?1, which was apparently free from the influence of the heat of adsorption of both benzyl alcohol and oxygen.     

An efficient and general synthesis of pyrroles

We have discovered that a wide range of 3-alkynyl-hydroxyalkanamine derivatives undergo 5-endo-dig cyclisations when exposed to silver nitrate supported on silica gel. Subsequent in situ dehydration of the resulting and sometimes isolable hydroxy-dihydropyrroles leads to pyrroles in essentially quantitative yields using this recoverable and reusable heterogeneous catalyst.     

Hydroxypropylcellulose-aceclofenac conjugates: high covalent loading design, structure characterization, nano-assemblies and thermal kinetics

This article presents synthesis of novel macromolecular prodrugs of aceclofenac (an anti-inflammatory drug) onto hydroxypropylcellulose (HPC). The HPC-aceclofenac conjugates were prepared using an acylating agent 1,1′-carbonyldiimidazole (CDI) under homogenous reaction conditions. Aceclofenac was first activated by using CDI to form its N-acylimidazole. The N-acylimidazole of aceclofenac was then reacted with HPC polymer at 80 °C for 24 h. Highly pure prodrugs of aceclofenac were synthesized with a wide range of moderate to high degree of substitution (DS 0.41–2.12) as calculated by ¹H NMR spectroscopy. The UV spectroscopic analysis has also revealed that the active drug aceclofenac was found in different conjugates from 28 to 67 mg/100 mg of HPC-aceclofenac conjugates which are in good agreement with DS calculated by ¹H NMR spectroscopy. The gel permeation chromatography showed unimodal absorption that indicates no significant degradation in polymer chains during the reaction. The macromolecular prodrugs of aceclofenac were characterized using different spectroscopic and chromatographic techniques. The thermal analysis has revealed that HPC-aceclofenac conjugates (prodrugs) are 92 and 96 °C more stable than pure aceclofenac regarding their initial (Tdi) and maximum degradation temperatures (Tdm), respectively. The activation energy (Ea) and frequency factor (Z) of the degradation reactions were evaluated using Friedman, Broido and Chang methods. Degradation followed first order (n) kinetics. Transmission electron microscopy has revealed the formation of sponge like nano aggregates with population size distribution of around 80–150 nm.     

Two New Octulosonic Acid Derivatives and a New Cyclohexanecarboxylic Acid Derivative from Erigeron bonariensis L.

The AcOEt‐soluble part of a MeOH extract from the whole plant of Erigeron bonariensis yielded two new rare‐class octulosonic acid derivatives, rel‐methyl (1R,2S,3S,5R)‐3‐(trans‐caffeoyloxy)‐7‐[(trans‐caffeoyloxy)methyl]‐2‐hydroxy‐6,8‐dioxabicyclo[3.2.1]octane‐5‐carboxylate ( 1 ) and 5,8‐di[O‐trans‐caffeoyl]‐3‐deoxy‐β‐D ‐gluco‐oct‐2‐ulopyranosonosyl 4,8‐di[O‐trans‐caffeoyl]‐3‐deoxy‐β‐D ‐gluco‐oct‐2‐ulopyranosidonic acid ( 2 ) along with a cyclohexanecarboxylic acid derivative, (1α,3β,4β,5β)‐1,4‐di‐3,5‐dihydroxy‐bis(trans‐caffeoyloxy)cyclohexanecarboxylic acid ( 3 ). The structures of these compounds were elucidated through ESI‐MS, and 1D‐ and 2D‐NMR spectroscopic techniques including ¹H‐ and ¹³C‐NMR, HMQC or HSQC, and HMBC experiments.