Abstract The reaction of 1, 1-dichloroethane with tellurium in the system hydrazine hydrate- potassium hydroxide gave ethyltellanyl derivatives as a result of replacement of one chlorine atom in the substrate by tellurium, and of the other, by hydrogen. Probable mechanisms of reduction of the C-Cl bond and mass spectra of the products were considered. The mass spectra of ditelluroacetals revealed unusual rearrangement of the molecular ion, leading ...