Effect of temperature on chlorproguanil and proguanil hydrochloride solutions: A chemical stability study

Chlorproguanil and proguanil hydrochloride solutions in 0.5 M hydrochloric acid, water and 1 M ammonium hydroxide were subjected to different temperatures (22–80°C) for 68 h. The decomposition rate constants for chlorproguanil ranged from 1.60 to 47.6 × 10 3 h −1 in acid, 3.5 to 18 × 10 3 h −1 in water and 3.87 to 32.5 × 10 3 h −1 in base, between 50°C and 80°C. The activation energy E a was 96.5, 52.12 and 62.1 kJ mol −1 in acid, water and base respectively. The proguanil decomposition rate constant ranged from 1.72 to 18.5 × 10 3 h −1 in acid, 1.58 to 9.67 × 10 3 h −1 in water and 2.34 to 15.77 × 10 3 h −1 in base, between 50°C and 80°C, with E a values of 54.7, 73.3 and 62.5 kJ mol −1 . Three unidentified degradation products were separated in the acid solution for each of the compounds. Chlorproguanil and proguanil are stable ( t 1 2 values over 30 days and up to 287 days respectively) in acid, water and base at temperatures below 22°C.