Hydrolysis of anhydride

Preparation Sign in at www.cengage.com/login to answer Pre-Lab Exercises, access videos, and read the MSDSs for the chemicals used or produced in this procedure. Review Sections 2.9, 2.10, and 2.17. 

Apparatus A 25-mL Erlenmeyer flask, ice-wafer bath, apparatus for vacuum filfra-tion, and ffame/ess heating. 

Setting Up Place 1.0 g of anhydride 6 and 5 mL of distilled water in the Erlenmeyer flask and add a stirbar. 

Hydrolysis and Isolation Heat the mixture to boiling and continue heating until all the oil that forms initially dissolves. Allow the solution to cool to room temperature and then induce crystallization by scratching the flask at the air-liquid interface. After 

Analysis Weigh the product to determine the yield, and measure its melting point. Test the product for unsaturation using the bromine in dichloromethane (Sec. 25.8A) and the Baeyer tests (Sec. 25.8B) to determine whether hydrolysis has affected the carbon-carbon Tr-bond. Also test a saturated aqueous solution of the diacid with pHydrion paper and record the result. Obtain IR and NMR spectra of your product and compare them with those of an authentic sample (Figs. 12.11 and 12.12). 

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ATP — ADP + P both represent hydrolysis of anhydride bond hydrolysis of ATP to ADP... 

The extraction of environmental or geological particulate matter with solvents, solvent mixtures or supercritical carbon dioxide is the preferred method, because it results in minimum alteration of its polar components, avoids hydrolysis of anhydrides, esters, etc. and is highly efficient for most organic compounds (even sugars). Other workers have reported the direct vaporization by thermal desorption or flash pyrolysis of organic compounds from particulate matter into GC, MS, or GC-MS instruments. Those methods work fine for neutral compounds (e.g. hydrocarbons) but should be used with caution when analyzing polar or labile compounds. 

As the loading of STA on the catalyst support is decreased, incomplete anhydride conversion is observed and significant hydrolysis of the anhydride to form iso-butyric acid is observed (Table 2). Use of silica supported phosphoric acid results in lower ketone yields and significant hydrolysis of the iso-butyric anhydride. Blank reactions (catalyst and anhydride, 90°C, 30 min) indicates that hydrolysis of anhydride is observed in the presence of these catalysts and may result from either dehydroxylation of the silica support or residual water in the catalyst, ffowever this reaction is slow (42%STA/silica, 44% conversion and 70%P[3PO4/silica, 86% conversion respectively). 

The reactivity of acidified chlorite solutions is reduced for bleaching some textiles by adding compounds like polyamines, pyrophosphates, and hydrogen peroxide that suppress the formation of chlorine dioxide (57). Another method is to buffer the solution at pH 5—6 to reduce the rate of chlorine dioxide formation. Hydrolysis of anhydrides and esters or oxidation of alcohols can be used to slowly generate acids to promote chlorine dioxide formation (58). Aldehydes also promote chlorine dioxide generation from neutral chlorite solutions, but the effect is greater than simply lowering the pH as they... 

Although, so far in this section, we have discussed the kinetic evidence in terms of the A-l and A-2 mechanisms favoured by Bunton et al. (p. 224), the same points which give rise to differences in detailed interpretation of mechanism for hydrolysis of acyl halides apply with equal weight to the hydrolysis of anhydrides. Butler and Gold67,68,298,299 have studied the spontaneous hydrolysis of acetic anhydride and presented the following scheme. 

The reaction mechanism for the hydrolysis of anhydrides is presumed to be similar to that described for acid chlorides (Scheme II). A notable difference between the reaction of acid chlorides and anhydrides, however, is the extent of reversibility in formation of 2. The reaction between 2 and chloride ion to give acid chloride (reversal of intermediate formation equation 2) is much less favored than the corresponding reaction between 2 and the carboxylate ion in both organic and aqueous phases. 

Values of k2lks = 2kjkii which are smaller than unity indicate that the addition step ( i) is rate-determining. Examples where k characterises the slow step are the alkaline, neutral, and acid hydrolyses of oxygen esters, the acid hydrolysis of amides and anhydrides, and the neutral hydrolysis of anhydrides, acid chlorides, and acetylimidazolium ion. 

Entering anhydride concentration, moles/cm Volumetric feed rate, cm /min % hydrolysis of anhydride r, °C... 

Hydrolysis of anhydride may be followed by measuring the decrease in the anhydride peak near 1850 cm-1. Although the peak is extremely small, it can be expanded for measurement without any significant sign of interference from... 

Fig. 70 Hydrolysis of anhydride ring in a NBTBE-MA copolymer during aqueous base development [261]...

The hydrolysis of anhydrides is in many ways similar to the hydrolysis of esters. The volume of activation for the acid-catalyzed hydrolysis of acetic anhydride in 44-1% w/w acetone-water at 0°C is —17T l-3 cm mole (Koskikallio et al., 1959). The volume of activation for the hydrolysis of methyl acetate in the same solvent is — 13-6 cm mole- (Withey et al., unpublished), and so it seems likely that the mechanism for acetic anhydride is bimolecular. This was originally taken as a failure of the Zucker-Hammett hypothesis (Koskikallio et al., 1959) because the rate in water is approximately proportional to (Gold and Hilton, 1955). However, it appears (Bunton and Perry, 1960), largely on the grounds of the changing entropy of activation with changing solvent, that the mechanism may change between pure water and aqueous dioxane. 

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