Bromine nuclear magnetic resonance study of the reorientation of bromomercurio–N-acetyl-L-phenylalanine, bromomercuriocinnamic acid, bromomercuriobenzoic acid and bromomercuriomethane in water

Abstract

Bromine nuclear magnetic relaxation times have been measured for aqueous solutions of KBr at 298 K, containing the bromomercury compounds bromomercuriocinnamic acid (CIN), bromomercurio-N-acetyl-L-phenylalanine, bromomercuriobenzoic acid and bromomercuriomethane. Br^– exchanges rapidly with the bromomercury compounds. Average spin-lattice relaxation times of ⁷⁹Br and ⁸¹Br have been measured for solutions containing CIN between 273 and 253 K. Correlation times (τ_rot≈10^–10 s at 298 K) for reorientation of the compounds are probably shorter than the pre-exchange lifetimes of bromine on the compounds. The high activation energy (E_rot= 45 kJ mol^–1) for reorientation measured for CIN suggests that hydrogen bonds are broken during the reorientation.