Abstract: Four aromatic naphthalenediazonium salts have been synthesised with the formula as: p-RC_(10)H_6N_2BF_4 (R=—H(Ⅰ), —NO_2(Ⅱ), —Br (Ⅲ), —N=N—C_6H_5(Ⅳ)). The thermal stability of the four diazonium salts is higher at room temperature and/or between certain temperature range, however they decomposed in the temperature range of 100-145 ℃. The thermal stability of the four diazonium salts correlated to their substituents is discussed. The possible mechanism of their thermal decomposition is presented. The order of the thermal stability of the four diazonium salts is: —NO_2(II)>—Br(III)>—N=N—C_6H_5(IV)>—H(I), and it is in consistent with the electron-withdrawing capability of the substituents. Some kinetic parameters of this reaction are determined also in this work. When diazonium salts (I), (II) and (III) react with NaBH_4, Then CIDNP signals have been detected with an improved NMR device. It shows that free radical processed play an important rote in thermal reductions of these diazonium salts with sodium borohydride.
From our experiment results the possibitity of diazonium salts (I)、(II) and (III) used as thermal sensitive materials may be promised.