GRAPHICAL ABSTRACT ABSTRACT Stable phosphonium salts were synthesized by the phosphorylation of a series of ω-haloalkylcarboxylic acids with triphenylphosphine. In a second step the resulting phosphonium salts have been treated with 1 M aqueous solution of sodium hydroxide to form the corresponding carboxylate phosphabetaines. The structure of the isolated compounds was determined by IR and NMR spectroscopy, elemental analysis, and X-ray crystallographic studies. Their thermal stability was studied by simultaneous thermogravimetry and differential scanning calorimetry.

The nucleophilic addition reactions of tertiary phosphines and unsaturated carboxylic acids have led to the formation of mono- and dicarboxylate phosphabetaines containing an asymmetric carbon atom. The data of 1D and 2D NMR spectroscopy have revealed the presence of diastereotopic geminal protons of the CH₂ group adjacent to the chiral center in the obtained compounds. The values of spin-spin coupling constants of the vicinal hydrogen atoms have coincided with the dihedral angles values (X-ray diffraction analysis data).

Phosphonium salts and their corresponding phosphabetaines—ω-phosphonioalkanoates—with a large number of methylene units were obtained on the basis of the reaction of triphenylphosphine and ω-bromoalkanecarboxylic acids. Structure and composition of the reaction products was proved using IR and NMR spectroscopy, X-ray diffraction analysis, and elemental analysis data. For a number of compounds, antimicrobial activity and thermal stability were studied.