Theoretical study on thermal safety of preparing fluorobenzene by the Balz-Schiemann reaction and fluorodenitration reaction

The Balz-Schiemann is the method of synthesizing fluorobenzene, which is complex and involves several hazardous chemicals, such as hydrofluoric acid, hydrochloride, sodium nitrite and so on, confronted with a high risk of intoxication and explosion. A comparison study of the thermal safety of preparing fluorobenzene using the Balz-Schiemann and fluorodenitration schemes is made by the density functional theory (DFT) method at the B3LYP/6-31G(D) level. The thermal safety is analyzed with reaction rate and statistic thermodynamic functions of reactants (R), products (P), intermediates (IM) and transition states (TS). The pathways of both the two reactions are also calculated without any assumption. According to calculation results, the reaction rate constant of fluorodenitration reaction is tens orders of magnitude less than that of the Balz-Schiemann reaction. Computational results also suggest that fluorodenitration is a milder exothermic reaction with higher thermal safety, which have great significance in inherently safety design during chemical process.