Of methyl benzoate

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... 

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. 

Carter, O. L., McPhail, A. T. Sim, G. A. (1967) Metal-carbonyl and metal-nitrosyl complexes. Part V. The crystal and molecular structure of the tricarbonylchromium derivative of methyl benzoate, J. Chem. Soc. A, 1619-1626. 

The carbonyl group of methyl benzoate condenses with Na-HMDS 486 to give methoxytrimethylsilane 13a and 51% yield of N,0-bis(trimethylsilyl)benzamide 296 [99], which is also accessible by silylation of benzamide with TCS 14/triethyla-mine. Benzamide or N-silylated benzamide, however, are converted by Na-HMDS 486 in benzene and subsequent quenching with MesSiCl 14 into 34% N,0-bis(trimethylsilyl)benzamide 296, 24% crystalline N-silylated benzamidine 524, and HMDSO 7 [99] (Scheme 5.32). 

Figure 3. Hydrogenation of methyl benzoate to methyl cyclohexanoate with rhodium on y-alumina catalysts. (Reprinted from Ref. [24], 2003, with permission from Elsevier.)...

As mentioned above, methyl loss from ionized methoxymethyl derivatives of methyl benzoate is not restricted to the ortho-isomet 93. 2H labelling has shown that the mita and para compounds 96 also eliminate CH3 specifically from the methoxymethyl group. Interestingly, neither from the unsubstituted benzyl methyl ether 97 (X = H) nor from the X-substituted analogues 97 (X = CH2OH, NQ2) loss of CH3 is observed (21). Thus, the earbomethoxy function seems to play a decisive role in the dissociation process. 

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). 

Many other miscellaneous additions of alcohols have been described. Polar addition of methanol to 2//-pyrroles264 and to azepines265 has been observed. Photoaddition of methanol to the 1,3,4-oxadiazole 320 is followed by cycloelimination of methyl benzoate (321) to give the ylid 322.266 An adduct (323) of the ylid and the 1,3,4-oxadiazole has been isolated. Photoaddition of methanol to the quaternary ammonium salt 324 results in ring expansion and the formation of the azonine 325.267... 

The use of ester and formyl groups for this reaction is also possible. The reaction of methyl benzoates with olefins proceeds when the benzoates have electron-withdrawing substituents such as trifluoromethyl, cyano, and ester groups (Equation (8)).5,5a In the case of aldehydes, the reaction requires sterically hindered substituents such as tert-butyl and trimethylsilyl groups.6... 

Relationship between the force fields of methyl benzoate and Cr(CO)6 and that of 6-methyl benzoate Cr(CO)3... 

There is one report of competitive nucleophilic attack at the amide carbonyl in an Ai-acyloxy-A-aUtoxyamide. Shtamburg and coworkers have reported that MeONa reacted with Ai-acetoxy-A-ethoxybenzamide (159) in DME giving methyl and ethyl benzoate (160 and 161) (Scheme 26) . They attributed the formation of methyl benzoate to the direct attack of methoxide ion at the amide carbonyl rather than at nitrogen. The formation of 161 was attributed to a HERON reaction. Though not mentioned by the authors, it seems likely that under these aprotic conditions, 162 could also have been formed by methoxide attack at the acetate carbonyl leading to an anion-induced HERON reaction, by analogy with the reaction of Ai-acyloxy-Ai-alkoxyamides and aqueous hydroxide discussed above (Section IV.C.3.c)... 

The nitration of methyl benzoate runs unusually smoothly, but it is essential to keep the temperature within the specified limits, otherwise the yield falls at 50°, 193 g. of solid product is obtained, while at 70° the yield falls to 130 g. 

Methyl m-nitrobenzoate has been prepared by the esterification of m-nitrobenzoic acid 1 this method is, however, obviously much less satisfactory than nitration of methyl benzoate. Nitration by means of fuming nitric acid has also been applied to methyl benzoate,2 but the use of the ordinary nitration mixture of concentrated sulfuric add and concentrated nitric acid is more satisfactory. 

An optimised enzymatic synthesis of methyl benzoate in an organic medium was reported by Leszczak and Tran-Minh [43]. Methyl benzoate is part of the aroma of some exotic fruits and berries. The ester has been produced by direct esterification of benzoic acid with methanol in hexane/toluene catalysed by lipase from Candida rugosa. 

Nevertheless the results quoted above for the breakdown of dimethyl hemiorthobenzoate indicate that (kinetic) general acid catalysis should be detectable in the methanolysis of methyl benzoate (Bransted a = 0.49) and probably in the analogous hydrolysis of methyl benzoate. Therefore any mechanism proposed for these reactions must be able to account for this. 

Dudareva, N., Murfitt, L.M., Mann, C. J. et al. (2000). Developmental regulation of methyl benzoate biosynthesis and emission in snapdragon flowers. Plant Cell 12 949-961. 

In a comparable solution of benzoic acid the freezing point is depressed only twice the predicted amount, indicating only a normal acid-base reaction. Further, a sulfuric acid solution of methyl mesitoate when poured into water gave mesitoic acid, while a similar solution of methyl benzoate similarly treated did not.534 The AacI mechanism is also found when acetates of phenols or of primary alcohols are hydrolyzed in concentrated (more than 90%) H2SO4 (the mechanism under the more usual dilute acid conditions is the normal Aac2).535... 

On the other hand, formation of methyl benzoate was also found to occur in methanol, indicating that, together with a general base-catalysis to produce benzamide and with the intramolecular, orthoester mechanism (see p. 110) to give the nitrogenated sugars, a transesterification reaction takes place in which the alkoxide ions play an important role. This can be exemplified by the following sequence. 

Esters show similar behaviour. Hantzsch found the /-factor for ethyl acetate to be close to 2, and accurate determinations by Leisten also gave values close to 2 for ethyl and methyl benzoate and p-nitrobenzoate. In a solvent containing sufficient water, hydrolysis of the ester occurs. The reaction of methyl benzoate has a time of half-change of a few hours at 25°C in sulphuric acid containing about 0.07 M water, and Leisten actually used the increase in the / -factor, from 2 to 3, to follow the hydrolysis reaction, viz. 

---