Núcleo de Pesquisa em Produtos Naturais e Sintéticos, Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Brasil.
J Mass Spectrom. 2012 Dec;47(12):1648-59. doi: 10.1002/jms.3101.
In order to understand the influence of alkyl side chains on the gas-phase reactivity of 1,4-naphthoquinone derivatives, some 2-hydroxy-1,4-naphthoquinone derivatives have been prepared and studied by electrospray ionization tandem mass spectrometry in combination with computational quantum chemistry calculations. Protonation and deprotonation sites were suggested on the basis of gas-phase basicity, proton affinity, gas-phase acidity (ΔG(acid) ), atomic charges and frontier orbital analyses. The nature of the intramolecular interaction as well as of the hydrogen bond in the systems was investigated by the atoms-in-molecules theory and the natural bond orbital analysis. The results were compared with data published for lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone). For the protonated molecules, water elimination was verified to occur at lower proportion when compared with side chain elimination, as evidenced in earlier studies on lapachol. The side chain at position C(3) was found to play important roles in the fragmentation mechanisms of these compounds.
为了了解烷基侧链对 1,4-萘醌衍生物气相反应性的影响，通过电喷雾串联质谱联用计算量子化学计算，合成了一些 2-羟基-1,4-萘醌衍生物并进行了研究。基于气相碱度、质子亲和能、气相酸度（ΔG(acid)）、原子电荷和前线轨道分析，提出了质子化和去质子化的位置。通过原子在分子中的理论和自然键轨道分析研究了体系中分子内相互作用和氢键的性质。将结果与已发表的拉帕醇（2-羟基-3-（3-甲基-2-丁烯基）-1,4-萘醌）的数据进行了比较。对于质子化分子，与早期拉帕醇的研究结果一致，水消除的比例比侧链消除低，被证实发生。在这些化合物的断裂机制中，C(3)位的侧链被发现起着重要的作用。
