Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, P.R. China.
Sci Rep. 2017 Aug 9;7(1):7675. doi: 10.1038/s41598-017-08217-1.
1-Pyrroline has a highly characteristic odor, which is employed by living organisms for chemical signaling and other purposes, but the mechanism whereby this odor is formed remains poorly understood. Here we used a combination of ambient mass spectrometry (AMS) and nuclear magnetic resonance (NMR) spectroscopy to experimentally address the mechanistic aspects of 1-pyrroline volatility and other controversies regarding the chemistry of this compound. Our results indicate that in solution the volatility of the monomer species is significantly higher than that of the trimer species, and 1-pyrroline is evaporated mainly in its monomer state. Neat 1-pyrroline is essentially the pure trimer and displays ca. 100-fold lower evaporation rate than the monomer state in solution. In the gas-phase the trimer species is irreversibly decomposed into monomer species. Under equilibrium conditions the vapor of 1-pyrroline entirely consists of monomer species. The evaporation rate of 1-pyrroline in water has a step-wise dependence on the solution pH, the abrupt increase in volatility (>1,000-fold) occurring around the pKa value of 1-pyrroline (6.8). The pronounced step-wise dependence of 1-pyrroline volatility around neutral pH may also be an important evolutionary factor allowing living systems to regulate the odor strength from very weak to very strong with minimal efforts.
吡咯啉具有高度特征性的气味，生物体将其用于化学信号传递和其他目的，但形成这种气味的机制仍知之甚少。在这里，我们使用环境质谱 (AMS) 和核磁共振 (NMR) 光谱学的组合，从实验上解决了 1-吡咯啉挥发性的机制方面以及关于该化合物化学性质的其他争议。我们的结果表明，在溶液中，单体物质的挥发性明显高于三聚体物质的挥发性，并且 1-吡咯啉主要以单体状态蒸发。纯 1-吡咯啉基本上是纯三聚体，在溶液中的蒸发率比单体状态低约 100 倍。在气相中，三聚体物质不可逆地分解成单体物质。在平衡条件下，1-吡咯啉的蒸气完全由单体物质组成。1-吡咯啉在水中的蒸发速率对溶液 pH 值具有逐步依赖性，在 1-吡咯啉的 pKa 值（6.8）左右，挥发性突然增加（>1000 倍）。1-吡咯啉在中性 pH 值周围的明显逐步依赖挥发性也可能是一个重要的进化因素，使生命系统能够以最小的努力将气味强度从非常微弱调节到非常强烈。
