三氨基三硝基苯(TATB)具有出色的安定性, 机械感度极低, 作为重要组分应用于核武器的高聚物黏结炸药(PBX). 然而, 目前工业制备TATB的主要方法存在效率低、杂质残留等问题. 基于以间苯三酚为原料的TATB的新合成路线, 我们发明了一种连续化高效制备TATB前体三乙氧基三硝基苯(TETNB)的方法. 鉴于该反应的重要性, 在M062X/6-31+G**水平上对其反应机理进行了深入的理论研究, 阐明了原甲酸三乙酯作为烷基化试剂进行烷基化反应的详细反应机理, 反应的关键中间体是二乙氧基碳正离子, 关键反应过程是双分子亲核取代(S_N2)和芳香亲核取代(S_NAr). 研究发现, 和反应物相比, 醚化产物在热力学上是稍微不利的, 达到平衡时产物所占比例较小. 因此, 实验中要不断移除副产物乙醇和甲酸乙酯, 拉动平衡向产物方向移动.

1,3,5-Triamino-2,4,6-trinitrobenzene (TATB) has excellent stability and very low mechanical sensitivity and is used as an important component in polymer binder explosive (PBX) for nuclear weapons. However, at present, the methods of industrial preparation of TATB have problems such as low efficiency and residual impurities. Based on a new method to synthesize TATB from phloroglucinol, we developed a continuous and efficient method for preparing 1,3,5-triethoxy-2,4,6- trinitrobenzene (TETNB), the key intermediate to synthesize TATB. In view of the importance of this reaction, in-depth theoretical research on the reaction mechanism has been conducted with the Gaussian 16 software at the M062X/6-31+G** level. The reaction mechanism and the thermodynamic equilibrium of the etherification process were clarified. Under the catalysis of protic acid, triethyl orthoformate eliminates one ethanol molecule to form a diethoxy-carbocation intermediate. Since the lone pair electrons of the adjacent oxygen atoms can partially fill the empty p orbital of the carbocation, the diethoxy-carbocation intermediate is relatively stable. Subsequently, there are two reaction modes for diethoxy-carbocation. In the first mode, trinitrophloroglucinol (TNPG) anion acts as a nucleophile to attack the diethoxy-carbocation intermediate in S_N2 fashion, grabbing an ethyl carbocation and achieving the alkylation. In this mode, the diethoxy-carbocation intermediate directly provides an alkyl carbocation. In the second mode, addition reaction occurs between the TNPG negative ions and the diethoxy-carbocation intermediate to produce new orthoformate, which can be regarded as transesterification. Then, the ethanol molecule conducts an aromatic nucleophilic substitution (S_NAr) to replace the diethyl orthoformate on the aromatic ring and complete the alkylation. In comparison, diethyl orthoformate is a relatively better leaving group. In addition, this etherification reaction has a remarkable feature: the thermodynamic stability of the product is slightly worse than that of the reactants. Therefore the yield is lower when chemical equilibrium is reached. This requires continuous removal of the by-products of the system in the experiment to pull the chemical balance toward the direction of the product.