Anhydride Concentration

Sulfuric acid reacts with acetic anhydride to form acetylsulfuric acid (79). This reaction is favored by low temperature and high anhydride concentration. In cellulose acetylation, probably both sulfuric acid and acetylsulfuric acid exist and react with cellulose to form cellulose sulfate acid ester. 

A solution containing 0.25 kmol/m of acetic anhydride is to be hydrolyzed in a single CFSTR to give an effluent containing an anhydride concentration of 0.05 kmol/m. The volumetric flowrate is 0.05 m /min and the working volume of the reactor is 0.75 m. ... 

Show that the reactor temperature must be maintained at 34°C given that tlie reaction is first order with respect to anhydride concentration and the rate constant k can be determined from the relationship... 

The initial anhydride concentration was about 3 x 10 M, and the amine concentration was much larger than this. The reaction was followed spectrophoto-metrically, and good first-order kinetics were observed hence, the reaction is first-order with respect to cinnamic anhydride. It was not convenient analytically to use the isolation technique to determine the order with respect to allylamine, because it is easier to observe the cinnamoyl group spectrophotometrically than to follow the loss of amine. Therefore, the preceding experiment was repeated at several amine concentrations, and from the first-order plots the pseudo-first-order rate constants were determined. These data are shown in Table 2-1. Letting A represent... 

Phthalic anhydride will, in the presence of the V2O5 catalyst of Example 9.1, undergo complete oxidation with A772 = — 760kcal/mol. Suppose the complete oxidation is pseudo-first-order in phthalic anhydride concentration and that ln( k//) = 12.300—10,000/T. 

The rate of polymer erosion in the presence of incorporated anhydride and release of an incorporated drug depends on the pK of the diacid formed by hydrolysis of the anhydride and its concentration in the matrix (20). This dependence is shown in Fig. 7 for 2,3-pyridine dicarboxylic anhydride and for phthaUc anhydride. In this study, methylene blue was used as a marker. The methylene blue release rate depends both on the pK and on the concentration of diacid hydrolysis product in the matrix. However, at anhydride concentrations greater than 2 wt%, the erosion rate reaches a limiting value and further increases in anhydride concentration have no effect on the rate of polymer hydrolysis. Presumably at that point Vj, the rate of water intrusion into the matrix, becomes rate limiting. 

Calculate the changes in naphthalene and phthalic anhydride concentrations using equations 13.2.56 and 13.2.57. 

Phthalic anhydride concentration profile for two wall temperatures. 

The quenching reaction also forms acetic acid, but in a different stoichiometric ratio than the hydrolysis reaction. Thus it is possible to determine the acetic anhydride concentration at the time the sample was taken. 

The colour reaction of cholesterol and cholesterol esters with acetic anhydride and concentrated sulphuric acid provides the basis of the method attributed to Liebermann and Burchard. This reaction in not entirely specific for cholesterol or its esters because other sterols will also react. In its original form the reagent consists of acetic anhydride, concentrated sulphuric acid and glacial acetic acid and the intensity of the green colour is affected by the proportions of the reagents and the amount of water present. It is possible to achieve an increase in sensitivity if the reagent contains ferric ions. Various modifications of reagent composition have been used and some methods are fluorimetric. 

On the alloy surface the reaction proceeded both via the anhydride and formate intermediates (117). As the copper concentration was increased, the formate species dominated the reaction, until at 63% copper the CO/COj ratio was less than 0.1. This change was due to the decrease in the amount of anhydride formed with increasing copper and the corresponding increase in formate. Since only the anhydride decomposition produced CO, the relative amount of anhydride formed could be determined as a function of surface composition. This relationship is shown in Fig. 21 the anhydride concentration fell as the fourth power of the nickel concentration, suggesting the requirement of four nickel atoms for its stabilization. This value agreed with the earlier determination for the saturation density of anhydride intermediates on Ni(llO) (99). 

Acetic anhydride is often encountered as a solution in ace tie acid Figure 30-b shows the effect of acetic anhydride concentration im the liquid viscosity at 15 C and T75C- ... 

The consumption of epoxide and anhydride is the same during curing 36). The analysis of the conversion curves showed that curing reaction is second order with respect, to epoxide and anhydride concentrations, i.e. first order with respect to each reagent.,... 

Figure 1. Effect of succinic anhydride concentration on the e-NH2 groups modification and reduction...

Figure 2. Effect of cyclic acid anhydride concentration on the modification of e-NH2 groups in the yeast proteins maleic anhydride (O) citraconic anhydride (%).

As with amine cured epoxies, frequently the optimum properties of anhydride-epoxy systems are obtained at other than the calculated stoichiometric amount. This is because competing reactions occur, such as the reaction of the anhydride group with a hydroxyl group. Typically, optimum anhydride concentrations occur at 85 to 95% of stoichiometric concentrations. 

The reactivity of the epoxy-anhydride reaction is slow therefore, an accelerator is often used at 0.5 to 3 percent to speed the gel time and cure. Most often the accelerator is a tertiary amine, and the optimum concentration is dependent on the anhydride, the resin used, and the cure conditions. The accelerator concentration, like the anhydride concentration, is usually determined experimentally based on a specific set of end properties. 

Naphtho[2,l-c]-l,2,5-oxatellurazolium chlorides were converted to 2-methyl-naphtho[l,2-c]-l,3-tellurazoles upon treatment with sodium borohydride, acetic anhydride, concentrated hydrochloric acid, and finally concentrated ammonia1,2 (p.777). 

The reaction of the epoxy resin with phthalic anhydride using curezol catalyst, 3(2-ethyl-4-methylimidazolyl) propanenitrile. shows an exotherm with its minimum at 154°C and a curing time of five to six minutes depending on the concentration of phthalic anhydride (Figure 1). At mole ratios of epoxy/phthalic anhydride of 1.7-1, 2-1, and 3.5-1 a small exotherm appears at 117°C before the main exotherm at 154°C. This exotherm decreases in intensity with decreasing phthalic anhydride concentration. The heats of reaction for the curing process are given in Table I. 

The middle infrared region of the cured crosslinked polymers shows bands in the 3480 cm"i, the 1200-1300 cm" and the 1000-1100 cm l region, the latter two increase with phthalic anhydride concentration. A band at 1420 cm"l along with the 3480 cm i 0-H stretch band appears in the spectra of the epoxy resin cured with curezol only. This band is a weak band in the uncured epoxy resin and is interpreted to be associated with a secondary hydroxyl group arising from epoxy ring opening (1 ). Bands at 1080 cm"i and 1290 cm"i also are present and are probably the C-0 stretch... 

Upon addition of catalyst and heat, three changes appear in the near IR spectra. The epoxy band decreases rapidly, the 0-H band increases and the C=0 band at 1.91 shows a large increase (Tables II and III). Table II shows the effects of phthalic anhydride concentration. Using the 1.66 p M band as an internal standard according to the method of Henniker (14), the 1.91 p M carbonyl and the 1.42 p M hydroxyl were compared to the 1.66 p M C-H band. Increasing the concentration of phthalic anhydride causes an increase in the intensity of the carbonyl band which becomes a maximum at a mole ratio of 1.7 to 1. This carbonyl could be due to monoester or diester in the final product. The hydroxyl band at 1.42 p M on the other hand remains fairly constant. 

A polymer solution containing AN/MMA copolymer plus 5% (referred to polymer) of maleic anhydride gelled completely, indicating that the expected crosslinking actually took place. As the maleic anhydride concentration was reduced to 0.5%, fiber spinning was no longer a problem. However, at this low concentration the beneficial effect on carbon fiber properties was only minor (see Table 8). 

The most common reagent for nitration of benzene, simple alkylbenzenes and other less reactive compounds is a mixture of concentrated nitric and sulfuric acids. However, nitration of activated substrates, such as aniline, phenol or pyrrole, occurs with nitric acid alone or in water, acetic acid or acetic anhydride. Concentrated sulfuric acid can oxidize these substrates. A description of the use of other nitrating reagents is outside of the scope of this review, but can be found in Smith and March s Advanced Organic Chemistry29 or Larock s Comprehensive Organic Transformations30. 

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

Solution From the results of Example 4-7, the fraction hydrolyzed in the stream leaving the first reactor is 0.328. If the anhydride concentration leaving the first reactor is designated as C, and that leaving the second is C2, Eq. (4-6) applied to the second reactor is... 

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