Benzoic Acid → Benzoic Acid

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This Example describes the method used for making a reaction product of di-isopropanolamine, benzoic acid and succinic acid anhydride. A one-liter reaction flask was provided with a mechanical agitator, a thermometer and a DeanStark arrangement. 261.06 g (1.960 mol) of di-isopropanol amine (type S, BASF), 540.88 g (4.429 mol) of benzoic acid (Aldrich) and 69.69 g (0.696 mol) of succinic acid anhydride (Aldrich) were placed in the flask. A small quantity of o-xylene, approximately 60 ml, was added as entraining agent in order to remove the liberated water. The reaction mixture was kept in a nitrogen atmosphere and heated for 1 hour at 165° C., whereafter the reaction temperature was brought to 180° C. After 6 hours the temperature was reduced to 160° C. and the flask was evacuated to remove the o-xylene. After about 1 hour it was possible to tap off the reaction mixture. Analysis showed that the number-averaged molecular weight (Mn) was 583 and the weight-average molecular weight (Mw) was 733. The ratio between Mw and Mn (1.26) is indicative of the fact that a mixture of compounds has formed. In formula 1 below, the compounds that can form during the reaction between di-isopropanol amine, benzoic acid and succinic acid are diagrammatically indicated (it should be noted that formula 1 is the most probable structure of the resulting compounds). The reaction shows the formation of a mono-disperse compound. The ratio of the reactants as shown in the formula is associated with a selected value for n. This ratio need not be equal to the ratio for the overall reaction, which is, in fact, a mixture of compounds with different values for n forms. In the reaction according to this example, a ratio has been selected equal to 2.82:6.36:1 (di-isopropanol amine: benzoic acid: succinic acid anhydride). This means that there are 3×2.82=8.46 mol-equivalents of reactive NH/OH groups in the amine, against 6.36+2×1.00=8.36 mol/equivalents acid groups in the benzoic acid and anhydride. There is therefore a very small excess (about 1%) of di-isopropanol amine.

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