Optimization of the Reaction Conditions for the Synthesis of Dihydrobenzofuran Neolignans

2020 ◽  
Author(s):  
Herbert Dias ◽  
Matheus Rodrigues ◽  
Antônio Eduardo Crotti
Keyword(s):  
Reaction Time ◽  
Oxidative Coupling ◽  
Methyl Esters ◽  
Dimethyl Ester ◽  
Intermediate Species ◽  
Radical Intermediate ◽  
Reaction Conditions ◽  
Experimental Conditions ◽  
Methyl Ferulate ◽  
Optimized Conditions

We have optimized the experimental conditions for the silver(I)-promoted oxidative coupling of methyl <i>p</i>-coumarate (<b>I</b>) and methyl ferulate (<b>II</b>), which is the most frequently used methodology to synthesize the bioactive dihydrobenzofuran neolignans <b>1</b> ((±)-<i>trans</i>-dehydrodicoumarate dimethyl ester) and <b>2</b> ((±)-<i>trans</i>-dehydrodiferulate dimethyl ester). Most of the tested conditions affected the conversion (i.e., the consumption of <b>I</b> and <b>II</b>) and the selectivity (i.e., the percentage of <b>I</b> and <b>II</b> that was converted into <b>1</b> and <b>2</b>, respectively), so the optimized conditions were the conditions that afforded the best balance between conversion and selectivity. Silver(I) oxide (0.5 eq) is the most efficient oxidant agent amongst the silver(I) reagents that were tested to convert methyl esters <b>I </b>and <b>II </b>into compounds <b>1</b> and <b>2</b>, respectively. Acetonitrile, which has not yet been reported as a solvent for this reaction, provided the best balance between conversion and selectivity, besides being “greener” than other solvents that are more often employed (e.g., dichloromethane and benzene). Under the optimized conditions, the reaction time decreased from 20 h to 4 h without significantly impacting the conversion and selectivity. However, the relation between the results obtained by adding a radical initiator (AIBN) or a radical inhibitor (isoquinoline) and the previously reported involvement of radical intermediate species in the silver(I)-promoted oxidative coupling of <b>I</b> and <b>II</b> is not clear and deserves further investigation.

Optimization of the Reaction Conditions for the Synthesis of Dihydrobenzofuran Neolignans

2020 ◽  
Author(s):  
Herbert Dias ◽  
Matheus Rodrigues ◽  
Antônio Eduardo Crotti
Keyword(s):  
Reaction Time ◽  
Oxidative Coupling ◽  
Methyl Esters ◽  
Dimethyl Ester ◽  
Intermediate Species ◽  
Radical Intermediate ◽  
Reaction Conditions ◽  
Experimental Conditions ◽  
Methyl Ferulate ◽  
Optimized Conditions

We have optimized the experimental conditions for the silver(I)-promoted oxidative coupling of methyl <i>p</i>-coumarate (<b>I</b>) and methyl ferulate (<b>II</b>), which is the most frequently used methodology to synthesize the bioactive dihydrobenzofuran neolignans <b>1</b> ((±)-<i>trans</i>-dehydrodicoumarate dimethyl ester) and <b>2</b> ((±)-<i>trans</i>-dehydrodiferulate dimethyl ester). Most of the tested conditions affected the conversion (i.e., the consumption of <b>I</b> and <b>II</b>) and the selectivity (i.e., the percentage of <b>I</b> and <b>II</b> that was converted into <b>1</b> and <b>2</b>, respectively), so the optimized conditions were the conditions that afforded the best balance between conversion and selectivity. Silver(I) oxide (0.5 eq) is the most efficient oxidant agent amongst the silver(I) reagents that were tested to convert methyl esters <b>I </b>and <b>II </b>into compounds <b>1</b> and <b>2</b>, respectively. Acetonitrile, which has not yet been reported as a solvent for this reaction, provided the best balance between conversion and selectivity, besides being “greener” than other solvents that are more often employed (e.g., dichloromethane and benzene). Under the optimized conditions, the reaction time decreased from 20 h to 4 h without significantly impacting the conversion and selectivity. However, the relation between the results obtained by adding a radical initiator (AIBN) or a radical inhibitor (isoquinoline) and the previously reported involvement of radical intermediate species in the silver(I)-promoted oxidative coupling of <b>I</b> and <b>II</b> is not clear and deserves further investigation.

Functionalization of poly(vinyl alcohol) by addition of methacryloyl groups: characterization by FTIR and NMR and optimization of reaction conditions by RSM

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Edson G. Crispim ◽  
Juliana F. Piai ◽  
Ivânia T. A. Schüquel ◽  
Adley F. Rubira ◽  
Edvani C. Muniz
Keyword(s):  
Reaction Time ◽  
Response Surface ◽  
Vinyl Alcohol ◽  
Poly Vinyl Alcohol ◽  
Reaction Conditions ◽  
Experimental Conditions ◽  
Molar Ratios ◽  
Gas Bubbling ◽  
Optimized Conditions ◽  
Hydroxyl Hydrogen

AbstractThe modification of poly(vinyl alcohol) (PVA) with glycidyl methacrylate (GMA) in DMSO catalyzed by TEMED is reported in this paper. PVA was dissolved in DMSO and reacted with GMA at 30 ºC in a closed vessel under N2 gas bubbling for 24 hours. The reaction was characterized by FTIR and NMR (1H, 13C/DEPT and HETCOR) spectroscopies. The reaction occurs by transesterification through the insertion of methacryloyl groups into PVA chains and probably with the formation of glycidol as a by-product. The degree of substitution (DS) that represents the number of methacryloyl groups inserted was determined through 1H NMR spectra based on the ratio between the averaged area due to the vinyl hydrogen from methacryloyl groups at δ̣ 5.6 ppm and δ 6.0 ppm and the total area of the vinyl hydrogen and hydroxyl hydrogen of PVA. By use of response surface methodology the experimental conditions were optimized. The optimum conditions were 62 ºC with a reaction time of 6 hours. In these optimized conditions, the reactions using the molar ratios [-OH(PVA)/GMA] equal to 1/0.10, 1/0.25, 1/0.50, 1/0.75 and 1/1 were investigated. The response surface was based on the model DS= −19.70 + 6.09x10−1T +1.93 t − 3.89x10−3 T2 − 5.21x10−2t2 − 2.14x10−2 T * t, where T is the temperature (°C) and t the reaction time (hours). This model explained 99.20 % of the 99.64 % explainable statistical data. Using the optimized conditions, it is possible to produce a desired modified PVA, (or PVA-Ma), because DS raises linearly to the ratio [-OH(PVA)/GMA] up to 25 mol-% and the respective yield ranged from 83 to 92 %. It is difficult to obtain more than 50 mol-% substitution of PVA hydroxyl by methacryloyl groups even in these optimized conditions due to increased steric hindrance by the large number of the methacryloyl groups inserted into PVA.

scholarly journals High-Quality Biodiesel Production from Buriti (Mauritia flexuosa) Oil Soapstock

Molecules ◽  
2018 ◽  
Vol 24 (1) ◽  
pp. 94 ◽  
Author(s):  
Samantha Pantoja ◽  
Vanessa Mescouto ◽  
Carlos Costa ◽  
José Zamian ◽  
Geraldo Rocha Filho ◽  
...  
Keyword(s):  
Reaction Time ◽  
Methyl Esters ◽  
Natural Antioxidants ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Palm Tree ◽  
Reaction Conditions ◽  
Mauritia Flexuosa ◽  
Buriti Oil ◽  
Brazilian Standard

The buriti palm (Mauritia flexuosa) is a palm tree widely distributed throughout tropical South America. The oil extracted from the fruits of this palm tree is rich in natural antioxidants. The by-products obtained from the buriti palm have social and economic importance as well, hence the interest in adding value to the residue left from refining this oil to obtain biofuel. The process of methyl esters production from the buriti oil soapstock was optimized considering acidulation and esterification. The effect of the molar ratio of sulfuric acid (H2SO4) to soapstock in the range from 0.6 to 1.0 and the reaction time (30–90 min) were analyzed. The best conditions for acidulation were molar ratio 0.8 and reaction time of 60 min. Next, the esterification of the fatty acids obtained was performed using methanol and H2SO4 as catalyst. The effects of the molar ratio (9:1–27:1), percentage of catalyst (2–6%) and reaction time (1–14 h) were investigated. The best reaction conditions were: 18:1 molar ratio, 4% catalyst and 14 h reaction time, which resulted in a yield of 92% and a conversion of 99.9%. All the key biodiesel physicochemical characterizations were within the parameters established by the Brazilian standard. The biodiesel obtained presented high ester content (96.6%) and oxidative stability (16.1 h).

Synthesis of Epoxidized Soybean Oil via Phase Transfer Catalysis

2013 ◽  
Vol 690-693 ◽  
pp. 1061-1064 ◽  
Author(s):  
Lu Jing ◽  
Guo Qin Liu ◽  
Xin Qi Liu ◽  
Xue De Wang
Keyword(s):  
Reaction Time ◽  
Soybean Oil ◽  
Phase Transfer Catalysis ◽  
Phase Transfer ◽  
Active Agent ◽  
Epoxidized Soybean Oil ◽  
Reaction Conditions ◽  
Epoxidation Reaction ◽  
Optimized Conditions ◽  
Epoxy Value

In the system of heteropoly acid [π-C5H5NC16H33]3[PO4(WO3)4], H2O2 (30 %, w/w), polyethylene glycol, 1,2-dichloroethane, soybean oil under went epoxidation reaction smoothly via reaction-controlled phase transfer catalysis. Effects of the amount of interfacial active agent, H2O2, catalyst and reaction time were investigated and the optimized reaction conditions were as follows: 10 g of soybean oil, 0.3 g of [π-C5H5NC16H33]3[PO4 (WO3)4],8 ml of H2O2 (30 %, w/w), 5.0 ml of PEG, 30 g of 1,2-dichloroethane, and the reaction temperature was 65 °C and reaction time was 3.5-4.0 h. Under these optimized conditions, an epoxy value of 6.30 % and a yield of 90 % were obtained. Hence, it is an environmental-friendly and effective way to synthesize epoxidized soybean oil.

Improve the Temperature Resistance of Guar Gum by Silanization

2011 ◽  
Vol 415-417 ◽  
pp. 652-655
Author(s):  
Jie Zhang ◽  
Gang Chen
Keyword(s):  
High Temperature ◽  
Reaction Time ◽  
Hydraulic Fracturing ◽  
Reaction Temperature ◽  
Guar Gum ◽  
Molar Ratio ◽  
Fracturing Fluid ◽  
Reaction Conditions ◽  
Temperature Resistance ◽  
Optimized Conditions

For gelating agent in hydraulic fracturing fluid, the temperature resistance is required. To improve the temperature resistance of Guar gum (GG), it was modified by silanization. The reaction conditions were investigated, and the optimized conditions were as following: the reaction temperature of 85°C, 5: 1 molar ratio of guar gum to TMS-Cl and 4-6 h of reaction time. The viscosity of silanized guar gum (SGG) aqueous gel was greatly improved even high temperature at 80°C.

scholarly journals Analysis of bilirubin and bilirubin mono- and di-conjugates. Determination of their relative amounts in biological samples

1980 ◽  
Vol 185 (1) ◽  
pp. 115-128 ◽  
Author(s):  
N Blanckaert
Keyword(s):  
Biological Samples ◽  
Methyl Esters ◽  
Dimethyl Ester ◽  
Crystalline Form ◽  
Reaction Products ◽  
Reaction Conditions ◽  
Normal Rat ◽  
Novel Method ◽  
Rat Bile

1. A novel method for determination of the relative amounts of unconjugated bilirubin and sugar mono- and di-conjugates of bilirubin in biological samples, including serum, is described and illustrated by its application to the analysis of bilinoids in rat bile. 2. The method is based on specific conversion of the carbohydrate conjugates of bilirubin into the corresponding mono- or di-methyl esters by base-catalysed transesterification in methanol. Under the selected reaction conditions, unconjugated biliru-in remains intact and no dipyrrole exchange in the bilinoids is detectable; transesterification of bilirubin mono- or di-glucuronide is virtually complete (approx. 99%), and sponification is negligible (less than 1%); recovery of the pigments is approx. 95%. 3. The reaction products bilirubin and its methyl esters are separated by t.l.c. and determined spectrophotometrically; the two isomeric bilirubin-IX alpha monomethyl esters are separated and therefore can be determined individually. 4. Reference bilirubin mono- and di-methyl esters have been synthesized and characterized, and the two isomers of bilirubin-IX alpha monomethyl ester and bilirubin dimethyl ester were obtained individually, in crystalline form. 5. With this new method, virtually all bilinoids (over 99%) in normal rat bile have been found to be conjugated, with diconjugates (71%) predominating. A significantly increased proportion of monoconjugates is present in bile collected from heterozygous Gunn rats or from normal rats that were refused with large amounts of bilirubin.

Optimization of Reaction Conditions for Preparing Carboxymethyl Cellulose Guaze

2013 ◽  
Vol 709 ◽  
pp. 40-44 ◽  
Author(s):  
Xi Hui Zhao ◽  
Qun Li ◽  
Ye Mi
Keyword(s):  
Fourier Transform ◽  
Reaction Time ◽  
Chemical Modification ◽  
Carboxymethyl Cellulose ◽  
Moisture Absorption ◽  
Large Degree ◽  
Reaction Conditions ◽  
Cotton Gauze ◽  
High Degree ◽  
Optimized Conditions

Chemical modification was employed for converting cotton gauze to carboxymethyl cellulose (CMC) gauze by treating them with sodium monochloroacetate and sodium hydroxide. Fourier Transform Infrared spectra (FTIR) were used to characterize the product. The reaction was optimized against temperature, concentration and reaction time for obtaining high degree of conversion. Under optimized conditions, the CMC gauze has a large degree of substitution (DS) of 0.43, and it has shown better moisture absorption ability than that of common cotton gauze.

REACTION OPTIMIZATION OF Aspergillus niger α-L-ARABINOFURANOSIDASE FOR IMPROVED ARABINOSE PRODUCTION FROM KENAF STEM

2017 ◽  
Vol 79 (4) ◽  
Author(s):  
Siti Norbaidurah Ayob ◽  
Abdul Munir Abdul Murad ◽  
Farah Diba Abu Bakar ◽  
Rosli Md Illias
Keyword(s):  
Reaction Time ◽  
Aspergillus Niger ◽  
Lignocellulosic Biomass ◽  
Hibiscus Cannabinus ◽  
Branching Enzyme ◽  
Enzyme Loading ◽  
Reaction Conditions ◽  
Reaction Optimization ◽  
Optimized Conditions ◽  
Central Composite

There are abundant of lignocellulosic biomass readily available with varying compositions. Kenaf (Hibiscus cannabinus) is one of this lignocellulosic biomass that has a high content of hemicellulose. This particular hemicellulose is composed of high arabinoxylan, which is a xylan backbone with arabinofuranosyl branches. In order to hydrolyze arabinoxylan, a branching enzyme is needed. Therefore, α-L-arabinofuranosidase from Aspergillus niger ATCC120120 (AnabfA) was used to hydrolyzed pre-treated kenaf and the reaction conditions were optimized using central composite design (CCD) to produce a significant amount of arabinose. There were 20 experiments conducted with 1.68 star points and 6 replicates at the centre points. The reaction conditions that were optimized are enzyme loading, substrate concentration and reaction time in which resulted with 88 U AnabfA activity, 0.9% (w/v) and 48 h, respectively. These optimized conditions managed to increase the yield of arabinose with 47.17 mg/g arabinose produced. 

scholarly journals Benchmarking Acidic and Basic Catalysis for a Robust Production of Biofuel from Waste Cooking Oil

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1050 ◽  
Author(s):  
Claudia Carlucci ◽  
Michael Andresini ◽  
Leonardo Degennaro ◽  
Renzo Luisi
Keyword(s):  
Reaction Time ◽  
Methyl Esters ◽  
Waste Cooking Oil ◽  
Molar Ratio ◽  
Experimental Conditions ◽  
Purification Method ◽  
Molar Ratios ◽  
Acidic Catalysis ◽  
Oil Mixtures ◽  
Industrial Level

The production of biodiesel at the industrial level is mainly based on the use of basic catalysts. Otherwise, also acidic catalysis allowed high conversion and yields, as this method is not affected by the percentage of free fatty acids present in the starting sample. This work has been useful in assessing the possible catalytic pathways in the production of fatty acid methyl esters (FAMEs), starting from different cooking waste oil mixtures, exploring particularly acidic catalysis. It was possible to state that the optimal experimental conditions required concentrated sulfuric acid 20% w/w as a catalyst, a reaction time of twelve hours, a temperature of 85 °C and a molar ratio MeOH/oil of 6:1. The role of silica in the purification method was also explored. By evaluating the parameters, type of catalyst, temperature, reaction time and MeOH/oil molar ratios, it has been possible to develop a robust method for the production of biodiesel from real waste mixtures with conversions up to 99%.

scholarly journals Optimization of an Ultrasonic-Assisted Biodiesel Production Process from One Genotype of Rapeseed (TERI (OE) R-983) as a Novel Feedstock Using Response Surface Methodology

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2656 ◽  
Author(s):  
Sara Almasi ◽  
Barat Ghobadian ◽  
Gholam Hassan Najafi ◽  
Talal Yusaf ◽  
Masoud Dehghani Soufi ◽  
...  
Keyword(s):  
Response Surface Methodology ◽  
Reaction Time ◽  
Response Surface ◽  
Methyl Esters ◽  
Operating Conditions ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Climate Conditions ◽  
Ultrasonic Assisted ◽  
Optimized Conditions

In recent years, due to the favorable climate conditions of Iran, the cultivation of rapeseed has increased significantly. The aim of this study was to investigate the possibility of biodiesel production from one genotype of rapeseed (TERI (OE) R-983). An ultrasonic approach was used in order to intensify the reaction. Response surface methodology (RSM) was applied to identify the optimum conditions of the process. The results of this research showed that the conversion of biodiesel was found to be 87.175% under the optimized conditions of a 4.63:1 molar ratio (methanol to oil), 56.50% amplitude, and 0.4 s pulses for a reaction time of 5.22 min. Increasing the operating conditions, such as the molar ratio from 4:1 to 5.5:1, amplitude from 50% to 72.5%, reaction time from 3 min to 7 min, and pulse from 0.4 s to 1 s, increased the FAME (fatty acid methyl esters) yield by approximately 4.5%, 2.3%, 1.2%, and 0.5%, respectively. The properties of the TERI (OE) R-983 methyl ester met the requirements of the biodiesel standard (ASTM D6751), indicating the potential of the produced biodiesel as an alternative fuel.

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