Introductory Halogenated aldehydes and ketones of the type RCO. CH2X e RC-(OH): CHX (X= halogen) include some of the most powerful lachrymatory compounds known, such as the halogenated acetones and chloroacetophenone used during the war as “tear gases.” Many years ago it was di~ covered~,~ that 2-aminothiazoles are obtained easily from such compounds by condensation with thio-ureas.