View all references with β-bromopropionic acid. The minimum loading of COOH of resin 3 verified by their FT-IR spectra exhibiting a strong carbonyl absorption at 1708ácm −1 was determined by acid-base titration[7]18. Schuerch , C. and Frechet , JM 1971. J. Am. Chem. Soc., 93: 492 [CrossRef] View all references to be 1.23ámmol COOH/g. Resin 3 can be stored at room temperature for long time without diminution of capacity or the liberation of disagreeable odors.