Introduction
Methyl butyrate or methyl ester of butyric acid is an ester with a fruity odor of pineapple, apple and strawberry. Present in small amounts in several plant products, especially pineapple flavor is produced by distillation from essential oils of vegetable origin. This ester is also manufactured on a small scale for use in perfumes or food flavors. Esters, in general, can be defined as the reaction products of carboxylic acids and organic alcohols. Chemically, an ester is the condensation product that results when a carboxylic acid is reacted with an alcohol1. Esterification of carboxylic acids with alcohols represents a well-known category of liquid-phase reactions of considerable industrial interest due to enormous practical importance of organic ester products. Esters are important fine chemicals used widely in the manufacturing of flavors, pharmaceuticals, plasticizers, solvents of paints, adhesives, pesticides, polymerization monomers and in the preparation of biodiesel from lower quality feedstock. Derivatives of some esters are useful as chemical intermediates and monomers for resins and high molecular weight polymers. They are also used as emulsifiers in the food and cosmetic industries2, 3.
Many routes are available for organic esters synthesis. The traditional route for preparing esters is via reaction of the carboxylic acid with an alcohol using homogeneous catalysts such as sulfuric acid or para-toluene-sulfonic acid4,5,6. Esterification can take place without adding catalysts due to weak acidity of carboxylic acids themselves. However, the reaction is extremely slow and requires long time to reach equilibrium at typical reaction conditions7. A common method of operating equilibrium limited reactions is to...
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...terification with methanol increases with an increase in temperature over the range of study (323-343 K); passes through maximum with increasing alcohol to acid ratio (1-4); increases with the increase in catalyst loading(0-8.5 % w/w). Conversion was optimum for the stirrer speed of 300 rpm indicating the absence of film diffusion. The conversion of butyric acid was dropped in the presence of added water due to inhibiting effect of water. The maximum conversion of 94.5 % was observed at optimum reaction conditions. Thus, the ion exchange catalyst was found to be very effective for the methyl butyrate synthesis. The Langmuir-Hinshelwood-Hougen-Watson Dual Site (considering reactants and products adsorbed on catalyst surface) heterogeneous model could be successfully applied for representing esterification kinetics for the reaction between butyric acid and methanol.
barbier reaction: In a 50 mL round bottom flask that had a reflux condenser attachment, saturated ammonium chloride (5 mL), THF (1 mL), zinc powder (0.4 g), benzaldehyde (0.500 mL, 0.5225 g, 4.92 mmol), and allyl bromide (0.470 mL, 0.6533 g, 5.40 mmol) were charged with stir bar and stirred at room temperature for 45 minutes. Diethyl ether (10 mL) was added to the reaction mixture and stirred. The mixture was gravity filtered into a beaker that was topped with a watchglass. The filtrate was transferred to a separatory funnel and the organic layer was extracted with deionized water (10 mL) and diethyl ether (15 mL). The organic layer was placed into an Erlenmeyer flask and the aqueous layer was placed into a beaker, which was extracted with
Solid triphenylmethanol (0.200 g, 0.768 mmol) and sulfuric acid (2 mL) were added to a reaction tube, which was then ground using a glass rod until it dissolved and turned a dark orange color. The mixture was then added dropwise via a glass pipette into another reaction tube containing methanol (1 mL). An extra amount of methanol (2 mL) was used to transfer the rest of the contents of the first reaction tube. Formation of crystals was facilitated by scratching the side of the tube and adding additional methanol until the color changed to an off-white color. The contents of the tube were then vacuum filtered with water and the resulting crude product was weighed and then recrystallized using hot methanol to form triphenylmethyl methyl ether (0.051 g, 0.186 mmol, 24.2%). The melting point was 81 – 83˚
The experimental Fischer esterification of 8.92g of acetic acid with 5.0g of isopentyl alcohol using concentrated sulfuric acid as a catalyst yielded 4.83g (65.3% yield) of isopentyl acetate. The product being isopentyl acetate was confirmed when the boiling point during distillation had similar characteristics to that of the literature boiling points2. Physical characteristics like color and smell also concluded a match of our product with what was intended. 1H-NMR spectroscopy analysis supported this claim due to the fact that the integration values and chemical shifts were comparable to isopentyl acetate. Lastly, infrared spectroscopy (IR) showed similar key characteristics of our product’s wavelengths to that of pure isopentyl acetate5.
The boiling point of the product was conducted with the silicone oil. Lastly, for each chemical test, three test tubes were prepared with 2-methylcyclohexanol, the product, and 1-decene in each test tube, and a drop of the reagent were added to test tubes. The percent yield was calculated to be 74.8% with 12.6g of the product obtained. This result showed that most of 2-methylcyclohexanol was successfully dehydrated and produced the product. The loss of the product could be due to the incomplete reaction or distillation and through washing and extraction of the product. The boiling point range resulted as 112oC to 118oC. This boiling point range revealed that it is acceptable because the literature boiling point range included possible products, which are 1-methylcyclohexene, 3-methylcyclohexene, and methylenecyclohexane, are 110 to 111oC, 104oC, and 102 to 103 oC. For the results of IR spectroscopy, 2-methylcyclocahnol showed peaks at 3300 cm-1 and 2930 cm-1, which indicated the presence of alcohol and alkane functional group. Then, the peak from the product showed the same peak at 2930 cm-1 but the absence of the other peak, which indicated the absence of the alcohol
The most classic and standard procedure for producing esters is the Fisher-esterification reaction. Discovered in 1895 by German chemists Emil Fischer and Arthur Speier 4, this reaction involves refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst. In order to drive the equilibrium towards the products, the water from the dehydration process must be removed and there must be an excess amount of alcohol. A vast range of carboxylic acids may be used for this reaction however the type of alcohols are limited. Primary and secondary alcohols are most frequently used in esterification reactions, tertiary alcohols are steric ally hindered usually resulting in poor yields5 and tend to undergo elimination reactions instead. In this rea...
Another simple improvement to the experiment could have been the addition of time to procedure A as well as possibly increasing the time heated under reflux. Since the entire procedure B had to be completed before the period of reflux was done, some of the steps and processes involved in procedure B were rushed or not given the adequate time allowed to produce the best sample of product. In general, the laboratory experiment was successful and turned out well to find that the bromide ion was the better nucleophile to both the n-butyl alcohol as well slightly toward the t-pentyl alcohol used in the
The purpose of the experiment was to study the kinetics of the hydrolysis of ester, p-nitrophenyl acetate (NPA) that is catalyzed by the buffer imidazole (Im). In terms of kinetics, specifically speaking, the rate of reaction as determined by the concentration, reaction orders, and rate constant with each species in a chemical reaction. By using the concentration of the catalyst and the temperature, the overall reaction rate was determined. The rate constants of K0, Kobs, and Kcat can be derived via the plotting of the absorbtion at 400nm of p-nitrophenol vs. the concentration of the catalyst imidazole. Lastly, the free energy of activation, ΔGǂ, that is necessary to force the reactant’s transformation of the reactants to the transition state structure will be determined by using the equation ΔGǂ = ΔHǂ – TΔSǂ derived from the Eyring plot.
The percentage yield gained was 70% from the Fischer Esterification reaction, which evaluates to be a good production of yield produced as the reaction is known to be reversible where conditions such as the concentration of the reactants, pressure and temperature could affect the extent of the reaction from performing. These white crystalline crystals were tested for impurity by conducting a melting point analysis and taking spectrospic data such as the IR spectra, HNMR and CNMR to confirm the identification of the product. These spectrospic methods and melting point analysis confirmed the white crystalline crystals were benzocaine.
The spots moved 3.8cm, 2.3cm, 2.1cm, 1.8cm, and 2.5 cm, for the methyl benzoate, crude product, mother liquor, recrystallized product, and isomeric mixture, respectively. The Rf values were determined to be.475,.2875,.2625,.225, and.3125, for the methyl benzoate, crude product, mother liquor, recrystallized product, and isomeric mixture, respectively. Electron releasing groups (ERG) activate electrophilic substitution, and make the ortho and para positions negative, and are called ortho para directors. In these reactions, the ortho and para products will be created in a much greater abundance. Electron Withdrawing groups (EWG) make the ortho and para positions positive.
The competing enantioselective conversion method uses each enantiomer of a kinetic resolution reagent, in this case R-HBTM and S-HBTM, in separate and parallel reactions, where the stereochemistry of the secondary alcohol is determined by the rate of the reactions. When using the CEC method, the enantiomer of the secondary alcohol will react with one enantiomer of the HBTM acyl-transfer catalyst faster than with the other HBTM enantiomer. The mnemonic that identifies the absolute configuration of the secondary alcohol is as follows: if the reaction is faster with the S-HBTM, then the secondary alcohol has the R-configuration. In contrast, if the reaction is faster with the R-HBTM, then the secondary alcohol has the S-configuration. Thin layer chromatography will be used to discover which enantiomer of HBTM reacts faster with the unknown secondary alcohol. The fast reaction corresponds to a higher Rf spot (the ester) with a greater density and a slower reaction corresponds to a lower Rf spot with high de...
Reacting 1-butanol produced 2-trans-butene as the major product. 1-butanol produces three different products instead of the predicted one because of carbocation rearrangement. Because of the presence of a strong acid this reaction will undergo E1 Saytzeff, which produces the more substituted
Chemical: Acids in foods and beverages such as citrus fruits, spices, wines and carbonated beverages; acids produced by acidogenic bacteria following carbohydrate exposure; acids from gastric regulation. (Wilkins, BS, RDH, DMD, 2013)
Predictions may be made about the suitability of possible catalysts by assuming that the mechanism of catalysis consists of two stages, either of which can be first:
The solution for the resistance to oxidation of p-toluic acid was solved by the discovery of bromide-controlled air oxidation in 1955 that was led to the implementation of AMOCO process [28-31]. In AMOCO process, the oxidation of para-xylene was conducted using a combination of three ions as a homogeneous catalyst which is cobalt, manganese and bromide ions. Acetic acid and oxygen/air were used as solvent and oxidant, respectively [32]. The common bromide ion sources are hydrobromic acid (HBr) and sodium bromide (NaBr). The oxidation operated at 175-225°C and 15-30 bar of oxygen. The terephthalic acid formed mostly in the form of solid due to the low solubility of terephthalic acid in the acetic acid. AMOCO process successfully gives a promising reaction yield, since more than 98% of para-xylene reacted, while terephthalic acid selectivity yield was about 95% in the reaction time of 8-24 hours (Scheme 3).
Emulsions are important in food science. Not only do they provide an important sensory aspect in many foods, but a functional one as well. From hollandaise to ice cream, getting hydrophobic and hydrophilic molecules to play nice with each other can be a difficult task. According to Modern Cuisine, it was previously thought that Hollandaise, a classic French emulsion of egg and butter, could only be made by letting butter drip from natural heat of the hand. Of course, modern science has taught us that, with the use of emulsifiers, these mystic mixtures can be created without the voodoo and magic once thought necessary. This paper will discuss emulsions as applied to hollandaise, chocolate, hot dogs and their characteristic pH, moisture content, shelf stability and quality of viscosity. An explanation of the chemical processes that occur between the raw ingredients of each food and the relationship between the structure and function of their components will be explained, as well as the importance of the chemical changes that take place during production. The characteristics that define these foods as emulsions will be compared and contrasted to further elucidate the mystery of the emulsion. Bon Appetite!