Determination of pKa Values for Acrylic, Methacrylic and Itaconic Acids by 1H and 13C NMR in Deuterated Water

Abstract

Acrylic, methacrylic and itaconic acids have Brønsted acidity given by carboxylic groups, and they are extensively used in polymerization for modification of several soft-mater materials. By this reason it is important to propose better characterization studies and alternatives to obtain more of their physicochemical properties. In this work the pKa values of these acids are obtained by adjusting NMR chemical shifts for hydrogen and carbon nuclei as a function of pH with program HYPNMR, and compared with those obtained by potentiometric and conductometric titrations.

Acid hydrogel matrixes as reducing/stabilizing agent for the in-situ synthesis of Ag-nanocomposites by UV irradiation: pH effect

“…It is known that sulfonic acids are much stronger acids than the corresponding carboxylic acids. For example, it was reported to MAA, which contain a carboxylic acid functional group, a value of pKa=4.46 [34] while AMPS, which contain a sulfonic acid (-SO 3 H) functional group, is dissociated completely in the overall pH range (EtSO 3 H, pKa (water)=−1.68) [29,35]. In addition, amide groups can change its ionized states in function of pH.…”

Control of Surface Morphology, Adhesion and Friction of Colloidal Gels with Lamellar Surface Interactions

“…The synthesis pH (≈2.0) is well below the pKa of methacrylic acid (≈4.6), and hence, very few carboxylic groups are expected to be dissociated during synthesis, which suggests that hydrophobic interactions may play a role during gelation. [ 16 ] The gels are then equilibrated in deionized (DI) water (pH 5.5) and heat treated for 20 h at 45 °C to increase homogeneity and reproducibility across measurements and reduce ageing effects during characterization. Mole ratios of 0.60‐0.95 methacrylic acid to total monomer (60‐95% mAAc) were selected in this work.…”

Radical Polymerization of Acrylates, Methacrylates, and Styrene: Biobased Approaches, Mechanism, Kinetics, Secondary Reactions, and Modeling

“…A special feature of the carboxyl group is that it can be in the ionized or nonionized form. The p K a value of acrylic acid is approximately 4.1 and for methacrylic acid is 4.7 . Ionization of acrylic and methacrylic acids influences k p .…”

“…The pK a value of acrylic acid is approximately 4.1 and for methacrylic acid is 4.7. 184 Ionization of acrylic and methacrylic acids influences k p . 185 The difference in k p values from nonionized and low concentration acid to either fully ionized or bulk polymerization is approximately 1 order of magnitude.…”