蒽醌、2-烷基蒽醌加氢热力学研究

Thermodynamic Study on Hydrogenation of Anthraquinone and 2-Alkylanthraquinone

结合量子化学计算综合分析了蒽醌、2-烷基蒽醌及其氢化产物分子的几何构型和电子结构,重点解析蒽醌及其衍生物分子于凝聚态体系原子的振动频率及各振动频率对热力学性质(熵和焓)的贡献,以此研究了不同烷基取代基对蒽醌分子在两步电子转移加氢过程中的加氢活性以及热力学平衡的影响。结果表明:蒽醌母体经2-乙基、2-叔丁基、2-叔戊基分别取代后,烷基蒽醌的氢化反应热明显增大,相同温度条件下2-乙基蒽醌、2-叔丁基蒽醌、2-戊基蒽醌的氢化反应热分别为-56.29、-62.7、-63.5 kJ·mol^(-1);328.15 K加氢温度条件下,蒽醌母体可完全转化为氢蒽醌,平衡转化率为100%,然而相同温度条件下2-乙基蒽醌、2-叔丁基蒽醌、2-叔戊基蒽醌的平衡转化率依次降低,分别为83.06%、60.58%、58.18%。

Combined with quantum chemical calculations, the geometric configuration and electronic structure of anthraquinone, 2-alkylanthraquinone and their hydrogenation products were comprehensively analyzed. The vibrational frequencies and vibrations of the atoms of anthraquinone and its derivatives in the condensed state system were investigated. Contribution of frequency to thermodynamic properties(entropy and enthalpy) was used to study the influence of different alkyl substituents on the hydrogenation activity and thermodynamic equilibrium of anthraquinone molecules in the two-step electron transfer hydrogenation process. The research results showed that the hydrogenation heat of alkyl anthraquinone increased significantly after the anthraquinone precursor was replaced by 2-ethyl, 2-tert-butyl, and 2-tert-amyl. Under the same temperature conditions, the hydrogenation heats of 2-ethylanthraquinone, 2-tert-butylanthraquinone and 2-pentylanthraquinone were respectively-56.29 kJ·mol^(-1),-62.7 kJ·mol^(-1),-63.5 kJ·mol^(-1);Under the conditions of hydrogenation temperature of 328.15 K, the anthraquinone precursor was completely converted into hydroanthraquinone, and the equilibrium conversion rate was 100%. However, the equilibrium conversion rates of 2-ethylanthraquinone, 2-tert-butylanthraquinone, and 2-tert-amylanthraquinone under the same temperature conditions decreased to 83.06%, 60.58% and 58.18%, respectively.