Nuclear magnetic relaxation in carboxylic acids

Spin-lattice relaxation times for the protons of the hydroxyl and methyl groups of acetic acid and for the protons of the hydroxyl, methyl and methylene groups of the propionic and butyric acids have been measured in order to find their dependence on the concentration of acids in carbon tetrachloride solutions and on temperature. The high resolution NPR spectrometer has been used, which operates at the frequency 25 MHz. Obtained results indicate that the process of the thermal relaxation of protons from the hydroxyl group is quite different from the relaxation of protons from methyl and methylen groups since there is the serious limitation of the motion of these two groups due to hydrogen bonds. (S.B.)