Hydrolysis of DCNP (a Tabun mimic) catalyzed by mesoporous silica nanoparticles

Abstract

[EN] The hydrolysis of diethylcyanophosphonate, DCNP (a Tabun simulant) in the presence of mesoporous silica nanoparticles (MSN) has been studied in acetonitrile:water (99.5:0.5 v/v) mixtures using 31P NMR as a suitable technique to follow the DCNP hydrolysis. MSN alone was not capable to induce DCNP hydrolysis, yet MSN in combination with the presence of the bases potassium carbonate, triethylamine or DABCO enhanced DCNP degradation. When MSN was used combined with K2CO3, a hydrolysis of ca. 95% of the initial DCNP after 60 min was observed. In the presence of DABCO, MSN was able to induce the hydrolysis of ca. 90% of DCNP after the same time. However, the DCNP hydrolysis using MSN in the presence of Et3N was lower (ca. 30%). In the absence of nanoparticles, DCNP hydrolysis reached only ca. 30% for K2CO3 and DABCO and ca. 7% for Et3N after 60 min. Moreover, kinetic studies were also carried out with the use of solids MSN-1 and MSN-2 that were obtained by reaction of MSN with K2CO3 or DABCO. After the reaction the solids were isolated by centrifugation, washed with acetonitrile and dried. MSN-1 was able to hydrolyse DCNP in a similar way to that found with the MSN-K2CO3 mixture. However, MSN-2 nanoparticles induced a very low DCNP hydrolysis. From all these studies it was found that the main product of the DCNP hydrolysis is tetraethylpyrophosphate. The presence of diethyl phosphoric acid was also observed but at very low concentration. From kinetic data a catalytic mechanism is proposed