Esters methyl benzoate

There are enthalpies of formation for two phases of cumyl perbenzoate. However, the associated sublimation enthalpy that interconnects these phases, 43 kJ mol , is much too small. In that the enthalpy of sublimation must exceed the enthalpy of vaporization, and the latter is at least 75 kJmol using the CHLP protocol (from the number of carbons alone), the enthalpy of formation data loses credibility. Furthermore, lacking the enthalpy of formation of the corresponding cumyl benzoate (in any phase) disallows comparison. This would seem to be an altogether normal species until it is recognized that the archetype arylcarboxylate ester, methyl benzoate, has provided complications for the calorimetrist . 

MURFITT, L. M., KOLOSOVA, N., MANN, C. J., DUDAREVA, N Purification and characterization of S-adenosyl-L-methionine Benzoic acid carboxyl methyltransferase, the enzyme responsible for biosynthesis of the volatile ester methyl benzoate in flowers of Antirrhinum majus., Arch Biochem. Biophys., 2000, 382,145-151. 

Pentamethoxyphosphorane, PfOCHj),. Mol. wt. 186.15, b.p. 37°. The material can be prepared in about 55% yield by reaction of trimethyl phosphite with methyl benzenesulfenate (which is converted during the reaction into diphenyl disulfide). It is stable to 80°. It reacts with acids to form methyl esters (methyl benzoate, 90% yield). It converts phenols into methyl ethers (anisole, 90% 2,4-dimethylanisole, 77% thioanisole, 87%). ... 

F.53) Benzoic acid, methyl ester, methyl benzoate (93-58-3] FEMA 2683... 

Benzoic acid, methyl ester methyl benzoate ... 

Our preliminary studies show that the catalyst system can tolerate at least some functionalities on the arene thus, while substrates containing unprotected -OH or COoH groups are hydrogenated only to a small degree or not at all, aryl-ethers (anisole), -esters (methyl benzoate), -ketones (acetophenone, benzophenone), and N,]V-dimethylaniline are all hydrogenated. In general, no products corresponding to states of intermediate reduction (cyclohexenes or cyclohexadienes) are detected. 

The spectrum of an unconjugated ester, isopentyl acetate, is shown in Figure 25.34 (C=0 appears at 1740 cm" ). A conjugated ester, methyl benzoate, is shown in Figure 25.35 (C=0 appears at 1720 cm" ). 

Ethyl benzoate hydrogen chloride as a catalyst). Pass dry hydrogen chloride (Section 11,48,1) into a 600 ml. round-bottomed flask containing 116 g. (145 ml.) of absolute ethyl alcohol, cooled in an ice bath, until the increase in weight is 6 g. Add 30 g. of benzoic acid and reflux the mixture for 4 hours. Isolate the pure ester, b.p. 212-214°, as described for Methyl Benzoate. The yield is 32 g. 

Mix 31 g. (29-5 ml.) of benzyl alcohol (Section IV, 123 and Section IV,200) and 45 g. (43 ml.) of glacial acetic acid in a 500 ml. round-bottomed flask introduce 1 ml. of concentrated sulphuric acid and a few fragments of porous pot. Attach a reflux condenser to the flask and boil the mixture gently for 9 hours. Pour the reaction mixture into about 200 ml. of water contained in a separatory funnel, add 10 ml. of carbon tetrachloride (to eliminate emulsion formation owing to the slight difference in density of the ester and water, compare Methyl Benzoate, Section IV,176) and shake. Separate the lower layer (solution of benzyl acetate in carbon tetrachloride) and discard the upper aqueous layer. Return the lower layer to the funnel, and wash it successively with water, concentrated sodium bicarbonate solution (until effervescence ceases) and water. Dry over 5 g. of anhydrous magnesium sulphate, and distil under normal pressure (Fig. II, 13, 2) with the aid of an air bath (Fig. II, 5, 3). Collect the benzyl acetate a (colourless liquid) at 213-215°. The yield is 16 g. 

The use of ether may be avoided by mixing the ester, after its isolation from the water layer, with about 20 ml. of carbon tetrachloride. The carbon tetrachloride solution then forms the lower layer in all washing operations (compare Methyl Benzoate, Section IV,176). 

Methylpyrazine reacts with sodamide in liquid ammonia to generate the anion, which may be alkylated to give higher alkylpyrazines (Scheme 10) (61JOC3379). The alkylpyrazines have found extensive use as fiavouring and aroma agents (see Section 2.14.4). Condensation reactions with esters, aldehydes and ketones are common, e.g. methyl benzoate yields phenacylpyrazine in 95% yield, and reactions of this type are summarized in Scheme 11. 

Aromatic Esters Ethyl benzoate Benzyl benzoate Methyl salicylate... 

Example 4.3. The p value for alkaline saponification of methyl esters of substituted benzoic acids is 2.38, and the rate constant for saponification of methyl benzoate under the conditions of interest is 2 x 10 s . Calculate the rate constant for the hydrolysis... 

Another example of enhanced sensitivity to substituent effects in the gas phase can be seen in a comparison of the gas-phase basicity for a series of substituted acetophenones and methyl benzoates. It was foimd that scnsitivtiy of the free energy to substituent changes was about four times that in solution, as measured by the comparison of A( for each substituent. The gas-phase data for both series were correlated by the Yukawa-Tsuno equation. For both series, the p value was about 12. However, the parameter r" ", which reflects the contribution of extra resonance effects, was greater in the acetophenone series than in the methyl benzoate series. This can be attributed to the substantial resonance stabilization provided by the methoxy group in the esters, which diminishes the extent of conjugation with the substituents. 

Alkali metal alkoxides, r-butyl acetate neat, 45°, 30 min, 98% yield of r-butyl ester from methyl benzoate. The rate constant for the reaction increases with increasing ionic radius of the metal and with decreasing polarity of the solvent. Equilibrium for the reaction is achieved in <10 sec. Other examples eire presented. " ... 

Ethyl Benzoate.—This ester has not been found, so far, to occur naturally in essential oils. It has, however, been prepared by synthetic processes, for example, by condensing ethyl alcohol with benzoic acid by means of dry hydrochloric acid gas. Its odour is very similar to that of methyl benzoate (q.v.), but not quite so strong. It is an oil of specific gravity I OfilO, refractive index 1 5055, and boiling-point 213° at 745 mm. It is soluble in two volumes of 70 per cent, alcohol. 

The benzene contains 80 g. of impure ethyl benzoate boiling at 180-260° and containing about 20 per cent of ethyl benzoylformate. In the case of the methyl ester the benzene contains 60 g. of impure methyl benzoate, boiling at 170-250°, and containing about 20 per cent of methyl benzoylformate. 

Finally, esters, for example methyl benzoate, are readily transesterified by excess alcohol, for example ethanol, in the presence of trimefhylsilyl iodide 17, in boiling chloroform, to give, via trimethylsilyl benzoate, the desired ethyl benzoate in 98% yield [117]. 

Hydrogenolyses of carboxylic acids and esters to the corresponding aldehydes seems very attractive due to their simplicity. Copper chromites are the most widely used catalysts.15 Raney copper and zinc oxide-chromium oxide have also been used for this process.16-18 The hydrogenolysis of methyl benzoate to benzaldehyde was studied on various metal oxides at 300-350°C. ZnO, Zr02 and Ce02 presented high activities and selectivities (Scheme 4.8). 

Following are the percentage yields obtained in the preparation of other esters ethyl maleate, 73 ethyl salicylate, 70 ethyl oxalate, 80 ethyl benzoate, 92 methyl benzoate, 87. In the preparation of ethyl maleate troublesome emulsions were encountered in working up the product. Occasionally this hap-... 

For example, dogs trained to detect cocaine often detect methyl benzoate, a product of the partial decomposition of cocaine when it is exposed to humid airJ2 Note that cocaine (Fig. 13.6.1) has two ester linkages these ester linkages are... 

Plots of the left-hand side of these equations against X are curved, allowing easy distinction of an A2 mechanism. Excess acidity plots using equation (59) are shown for some ester hydrolyses in sulfuric acid at 25°C in Fig. 10, for 1-butyl acetate,29 and for methyl 2,6-dimethylbenzoate and methyl benzoate.41 The first ester (leftmost line in Fig. 10) clearly undergoes an A1 hydrolysis, specifically AAil 29 the parameters of the line are slope 1.552 + 0.027 intercept... 

Fig. 10 Excess acidity plots against X for the hydrolyses of some esters in aqueous H2SO4 at 25°C for methyl benzoate (open circles) and methyl 2,6-dimethylbenzoate (closed circles), data from ref. 41, and for r-butyl acetate (open triangles), data from ref. 29. PCT, protonation correction term.

Now a very useful feature of the excess acidity method comes into play likely nucleophiles or bases can be tested by subtracting their log activities or concentrations from the left-hand side of equations (59) and (60), and the species reacting with SH+ is uniquely identified when linearity of the result against X is achieved.145,161 For instance, subtraction of twice the water activity is required to attain linearity in ester hydrolysis processes such as equation (42), as shown in Fig. 11 for methyl benzoate41 and ethyl benzoate.210 The water activities given in Table 3 were used. The parameters of the lines in Fig. 11, obtained by curve-fitting, are methyl benzoate, slope 0.921 + 0.010, intercept... 

As would be expected, the slopes are almost identical the intercept difference shows that methyl benzoate reacts about 1.5 times as fast as does ethyl benzoate in the standard state, a result easily attributable to the slight increase in steric crowding to the equation (42) hydrolysis in the latter case. The order of the A2 ester hydrolysis reaction in water is thus two, a result quite difficult to obtain in other ways, even in dilute solution, perhaps requiring a proton inventory study of a reaction that is very slow in water. 

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