Heterogeneous acid-catalysed isomerization of carvone to carvacrol (original) (raw)
Journal of the Brazilian Chemical Society, 2013
Uma nova rota catalítica, de potencial interesse prático para a produção sustentável de acetinas a partir do glicerol, é descrita. Acetato de etila foi transesterificado com glicerol, numa razão glicerol:EtOAc 1:10, a 25 ou 90 o C, usando 0,1 equivalente de H 2 SO 4 ou TsOH como catalisadores homogêneos. H 2 SO 4 levou ao consumo total de glicerol, a 90 o C, em 2 h. No equilíbrio, atingido em 9 h, 100% de uma mistura diacetina:triacetina (55:45) foi formada. Usando-se Amberlyst TM 15 seca e Amberlyst TM 16 úmida numa razão glicerol:EtOAc 1:30 sob refluxo a 90 ºC, obteve-se o consumo total do glicerol em 2 e 10 h, respectivamente. A menor reatividade da resina Amberlyst-16 úmida foi explicada pela desativação dos sítios ácidos e pela diminuição da difusão do glicerol para o interior dos poros, causada pela água adsorvida. A cinética da transformação do glicerol e a distribuição de produtos no equilíbrio para a reação catalisada por H 2 SO 4 , Amberlyst TM 15 seca e Amberlyst TM 16 úmida foram medidas e racionalizadas. A new catalytic route with potential practical interest to sustainable production of bioadditives from glycerol is described. Ethyl acetate was transesterified with glycerol, in the ratio glycerol:EtOAc 1:10, at 25 or 90 o C using 0.1 equiv. of H 2 SO 4 or TsOH, as homogeneous catalysts. H 2 SO 4 led to the total glycerol consumption in 2 h. In the equilibrium, attained in 9 h, 100% yield of a diacetin:triacetin (55:45) mixture was formed. Using Amberlyst TM 15 dry and Amberlyst TM 16 wet in 1:30 glycerol:EtOAc ratio and reflux at 90 ºC the total glycerol consumption was achieved in 2 and 10h, respectively. The lower reactivity of Amberlyst-16 wet was explained in terms of deactivation of acid sites and decrease in glycerol diffusion to the inner resin pores, both factors caused by adsorbed water. The kinetics of glycerol transformation and product distribution in the equilibrium in relation to the H 2 SO 4 , Amberlyst-15 (dry) and Amberlyst-16 (wet) catalyzed reactions were measured.
Biotechnology and Bioengineering, 2008
The microbial biotransformation of (À)-transcarveol to the flavor and fragrance compound (R)-(À)carvone by Rhodococcus erythropolis DCL14 was carried out in a 3 L two phase partitioning bioreactor with an immiscible liquid second phase in an effort to improve upon the reactor performance achieved in a single aqueous phase system. The purpose of employing the liquid second phase is to minimize biotransformation rate inhibition due to the accumulation of the toxic substrate (cis-carveol) and product (carvone) in the aqueous phase. 1-Dodecene was chosen as the solvent for this application because it is biocompatible, non-biodegradable and has a superior affinity for the target product (carvone) relative to the other solvents tested. However, when 1-dodecene was used in the biotransformation, the extremely hydrophobic R. erythropolis DCL14 created an emulsion with the organic solvent with significant sequestering of the cells into the organic phase and negligible substrate conversion. To overcome these operational difficulties, silicone oil, which is considered a liquid polymer, was used with the aim of preventing emulsification and sequestration of cells in the non-aqueous phase. Although some emulsification of the water-silicone oil was again created by the cells, operability was improved and, in fed-batch mode, the system was able to convert approximately 2½ times more carveol than a benchmark single aqueous phase system before substrate/ product toxicity caused the biotransformation to stop. This study has demonstrated enhancement of a microbial biotransformation for the production of a high value nutraceutical compound via the use of a second partitioning phase, along with operational challenges arising from the use of a highly hydrophobic organism in such systems.
Kinetics of acetalization of perfumery aldehydes with alkanols over solid acid catalysts
The Canadian Journal of Chemical Engineering, 1999
This paper highlights the importance of heterogeneous catalysis in the manufacture of fragrance and flavor chemicals, with theoretical and experimental analysis of acetalization reaction. The acetals of n-octanal with methanol and ethanol were prepared by using solid acids, such as Filtrol-24, Amberlyst-15, dodecatungstophosphoric acid (DTPA) supported on ZSM-5, as well as on K-10 clay. The efficacy of these catalysts per unit weight basis was in the following order:
Reaction Kinetics, Mechanisms and Catalysis
This work describes the isomerization of S-carvone using a natural zeolite-clinoptilolite as the catalyst. The isomerization of S-carvone was carried out at the catalyst content in the reaction mixture from 5 to 15 wt%, in a temperature range of 190-210 °C and for the reaction time from 60 to 300 min. The main product of the isomerization of S-carvone was aromatic alcohol with many practical applicationscarvacrol. The use of the most favorable reaction conditions (the reaction time of 3 h, the temperature of 210 °C and the catalyst content 15 wt%) allowed to obtain this compound with high yield amounted to about 90 mol%. The S-carvone isomerization is an example of environmentally friendly process because it does not use any solvents, S-carvone can be separated from cheap cumin waste (renewable biomass) and a cheap zeolite of natural origin-clinoptilolite can be is used as the catalyst.
Amberlyst-15 in organic synthesis
Arkivoc, 2012
Commercially available Amberlyst-15 has played an important role in organic synthesis. This review summarizes the versatile synthetic applications of Amberlyst-15 in different chemical transformations. Reactions include esterification, transesterification, Michael addition, aza-Michael addition, Prins cyclization, Friedel-Crafts alkylation, acylation, metal free hydroarylation, hydroalkylation, halogenation, protection of carbonyls, amines, deprotection of acetals, acetates, Boc-protected amines, cleavage of epoxides, crossed-aldol condensation, synthesis of quinolines, pyrazolines, indolinones, acridines, calix[4]pyrroles, xanthenes, coumarins, benzopyrans theaspirane, furans, and substituted phosphonates. Applications of this catalyst allow mild and highly selective transformations and synthesis in a facile and environmentally friendly manner. The catalysts can be regenerated and recycled.
Brønsted and Lewis Solid Acid Catalysts in the Valorization of Citronellal
Catalysts, 2018
Terpenes are valuable starting materials for the synthesis of molecules that are of interest to the flavor, fragrance, and pharmaceutical industries. However, most processes involve the use of mineral acids or homogeneous Lewis acid catalysts. Here, we report results obtained in the liquid-phase reaction of citronellal with anilines under heterogeneous catalysis conditions to give tricyclic compounds with interesting pharmacological activity. The terpenic aldehyde could be converted into octahydroacridines with a 92% yield through an intramolecular imino Diels–Alder reaction of the imine initially formed in the presence of an acidic clay such as Montmorillonite KSF. Selectivity to the desired product strongly depended on the acid sites distribution, with Brønsted acids favoring selectivity to octahydroacridine and formation of the cis isomer. Pure Lewis acids such as silica–alumina with a very low amount of alumina gave excellent results with electron-rich anilines like toluidine an...
Antimicrobial activity of carvacrol related to its chemical structure
Letters in Applied Microbiology, 2006
Aims: To investigate the relation between the chemical structure and the antimicrobial activity of carvacrol, eugenol, menthol and two synthesized carvacrol derivative compounds: carvacrol methyl ether and carvacryl acetate against bacteria, Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Lactobacillus plantarum, Bacillus subtilis, a yeast Saccharomyces cerevisiae and one fungi Botrytis cinerea. Methods and Results: The antimicrobial activity was tested in liquid and vapour phases, by both broth liquid and microatmosphere methods, respectively. The same classification of the compound's antimicrobial efficiency was found with both methods. Eugenol and menthol exhibited a weaker antimicrobial activity than carvacrol, the most hydrophobic compound. Carvacryl acetate and carvacrol methyl ether were not efficient, indicating that the presence of a free hydroxyl group is essential for antimicrobial activity. Conclusions: The different extents of antimicrobial aroma compounds' efficiency showed that hydrophobicity is an important factor and the presence of a free hydroxyl group and a delocalized system allows proton exchange. Significance and Impact of the Study: This study has identified the importance of the hydrophobicity and the chemical structure of phenolic aroma compounds for antimicrobial activity and may contribute to a most rational use of these compounds as antimicrobial agent.
Environmental Technology, 2017
Synthesis of bioadditives of fuels from biodiesel-derived glycerol by esterification with acetic acid on solid catalysts In this paper, glycerol esterification with acetic acid was studied on several solid acid catalysts: Al 2 O 3 , Al-MCM-41, HPA/SiO 2 , HBEA, Amberlyst-15 and Amberlyst-36 with the aim of determining the reaction conditions and the nature of the surface acid sites required to produce selectively triacetylglycerol (triacetin). The acidity of the catalysts (nature, density and strength of acid sites) was characterized by temperature programmed desorption of NH 3 and FTIR of adsorbed pyridine. Al 2 O 3 (Lewis acidity) did not show any activity in the reaction. In contrast, highest activity and selectivity to the triacetylated product (triacetin) were obtained on catalysts with Brønsted acidity: Amberlyst 15 and Amberlyst 36. The effect of temperature and molar ratio of acetic acid to glycerol was studied, finding that both parameters have a significant impact on the obtention of the desired product. Glycerol conversion rate and selectivity to triacetin increased when temperature or acetic acid to glycerol molar ratio were increased reaching a triacetin yield on Amberlyst 36 of 44% at 393 K and acetic acid to glycerol molar ratio of 6. Deactivation and reusability of Amberlyst 36 were evaluated by performing consecutive catalytic tests. The presence of some irreversible deactivation due to sulphur loss was observed. In addition, the feasibility of using crude glycerol from biodiesel production as reactant was also investigated. Conversion of crude pre-treated glycerol yielded values of triacetin and diacetin similar to those obtained with the commercial pure glycerol although at a lower rate.