Tetramethylguanidine covalently bonded onto silica gel as catalyst for the addition of nitromethane to cyclopentenone

Abstract

Um catalisador baseado em sílica quimicamente modificada com tetrametilguanidina (TMG) foi sintetizado pela co-condensação de tetraetilortossilicato (TEOS) com um novo agente sililante, preparado pela reação entre a molécula TMG e (3-cloropropil)trimetoxisilano. O direcionador n-dodecilamina foi utilizado para organizar a polimerização do catalisador inorgânico-orgânico. A termogravimetria mostrou que o número de sítios ativos do catalisador foi de 1,35 mmol g .A espectroscopia na região do infravermelho e de ressonância magnética nuclear no estado sólido para os núcleos 29 Si e 13 C confirmou a obtenção do produto desejado. Este material foi usado para catalisar a adição de nitrometano em ciclopentenona. 98% de conversão foi observada depois de 3 h de reação. O catalisador foi recuperado e reutilizado por mais catorze vezes, mantendo uma eficiência catalítica em torno de 98%.A catalyst based on silica chemically modified with tetramethylguanidine (TMG) was synthesized by the co-condensation of tetraethylorthosilicate (TEOS) with a new silylant agent derived from the reaction between the TMG molecule and (3-chloropropyl)trimethoxysilane. A neutral n-dodecylamine template was used to organize the polymerization of the inorganicorganic catalyst. Thermogravimetry showed that the number of active pendant groups in the catalyst was 1.35 mmol g -1 , with a surface area of 811 ± 75 m 2 g -1. Infrared spectroscopy and 13 C and 29 Si nuclear magnetic resonance data are in agreement with the proposed structure. This material has been used to catalyse the addition of nitromethane to cyclopentenone. The catalytic efficiency was followed and the nitromethylcyclopentanone conversion presented a yield of 98% at 3 h of reaction. The catalyst was recovered and reused 14 times, maintaining about 98% of its catalytic efficiency.

Modification of silica gel by attachment of 2-mercaptobenzimidazole for use in removing Hg(II) from aqueous media: A thermodynamic approach

“…the anchorage of the organic molecule onto the silica surface [16]. Thermogravimetric curves for SiM het and SiM hom are presented in Fig.…”

“…The well-characterized decomposition stages of SiM hom and SiM het were selected for study of the kinetics of decomposition. The kinetic parameters, activation energy (E) and pre-exponential factor (A), were calculated using the Coats-Redfern equation [16,22,23],…”

“…The surface area, pore diameter, and pore volume of materials were obtained using the nitrogen adsorption technique in a Micromerimetics ASAP 2010 porosimeter [16].…”

“…13 C and 29 Si nuclear magnetic resonance spectra of the solid samples were obtained on a Varian Mercury Plus 300 spectrometer at room temperature. The method and experimental details of NMR have been presented in detail elsewhere [16].…”

Infrared spectroscopy for analysis of co-processed ibuprofen and magnesium trisilicate at milling and freeze drying

“…A large broad band between 3550 to 3200 cm -1 ascribed to the presence of the O-H stretching frequency of silanol group bonded to the inorganic structure of MTS (containing SiO 2 ), and also hydrogen bonds between adsorbed water and silanol. 25,35 This large broad band is absent in ibuprofen pure drug but consistently maintained in all the co-processed materials could be due to intermolecular hydrogen bonding. The band related to the silanol (Si-O-Si) asymmetric stretching was found at 1027 cm -1 with high intensity in MTS and also in the co-processed formulations.…”