Benzoic Acid → Benzoic Acid

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This Example describes a process used for making reaction product 6 as indicated in Table 2, namely a reaction product of di-isopropanolamine, benzoic acid and succinic acid anhydride. A 1 liter reaction flask was provided with a mechanical agitator, a thermometer and a DeanStark arrangement. 261.06 g (1.960 mol) of di-isopropanolamine (type S, BASF) 540.88 g (4.429 mol) 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, about 60 ml, was added as entraining agent to remove the liberated water. The reaction mixture was kept under a nitrogen atmosphere and heated for 1 hour at 165° C., whereafter the reaction temperature was raised to 180° C. After 6 hours the temperature was reduced to 160° C. and the flask was evacuated to remove the o-xylene. It was possible to draw off the reaction mixture after about 1 hour. Analysis showed that the number-averaged molecular weight (Mn) was 583 and the weight-averaged molecular weight (Mw) was 733. The ratio between Mw and Mn (1.26) showed that there was a mixture of compounds formed. The diagram below (formula 1) indicates what compounds may form during the reaction between di-isopropanolamine, benzoic acid and succinic acid (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 in respect of reactants as indicated in the formula belongs to a chosen value for n. This ratio need not necessarily be identical to the ratio for the overall reaction, where in fact a mixture of compounds with different values for n is formed. In the reaction according to this example, a ratio has been chosen which is equal to 2.82:6.36:1 (di-isopropanolamine: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, as against 6.36+2×1.00=8.36 mol equivalents of acid groups in the benzoic acid and anhydride. There is therefore only a very small excess (about 1%) of di-isopropanolamine.

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