Data from GCA article "Thermodynamic property estimations for aqueous primary, secondary, and tertiary alkylamines, benzylamines, and their corresponding aminiums across temperature and pressure are validated by measurements from experiments"

Abstract: On Earth and beyond, organic chemistry often occurs in the presence of water within environments that deviate drastically from ambient conditions (25°C and 1 bar). Accurately predicting aqueous organic reaction pathways is crucial toward understanding planetary scale processes such as the cycling of elements crucial for life (e.g., carbon and nitrogen). Advanced thermodynamic modeling can be utilized to determine the favorability of various organic reactions based on geologically relevant ranges of temperature and pressure, as well as compositional variables (e.g., pH). However, data that would otherwise allow for a diversity of organic compounds and environmental conditions to be modeled are sparse and rarely tested with experiments, particularly with regard to organic-nitrogen compounds. In this work, we develop a framework to estimate thermodynamic properties at ambient conditions that can then be extrapolated across ranges of temperature and pressure for aqueous primary, secondary, and tertiary amines and aminiums (protonated amines), specifically those structures containing linear alkyl chains and benzyl functional groups. We also performed hydrothermal experiments (250°C, ~40 bar) involving reactions of methylamines to test our resulting thermodynamic models, and we compare our models for other alkylamines and benzylamines to previous empirical measurements from the literature. Specifically, we use existing thermodynamic data along with our estimates at ambient conditions in combination with a variety of existing extrapolation methods related to the revised Helgeson-Kirkham-Flowers (HKF) equations of state to generate temperature- and pressure-dependent predictions of acid dissociation constants (i.e., pKa values) that strongly agree with previous empirical measurements. We use similar methods to predict product distributions for reactions involving primary, secondary, and tertiary amines/aminiums, as well as ammonia/ammonium and corresponding alcohols whose collective distributions depend on reversible substitution reactions. Our predictions are in good agreement with our experimental results involving the methylamine reaction system as well as previous experiments involving the benzylamine reaction system, for which we also produced thermodynamic estimates involving benzyl alcohol. The agreement between independent theoretical predictions and experimental measurements suggests that our estimated properties can be applied to modeling amine chemistry in other experimental and natural aqueous systems that range in temperature and pressure, providing new tools for planetary exploration.

摘要：在地球及其他天体中，有机化学反应常发生于含水环境中，而此类环境与常温常压（25℃、1巴）的条件差异显著。精准预测水相有机反应路径，对于理解行星尺度的地球化学过程至关重要，例如维系生命的关键元素（如碳、氮）的生物地球化学循环。借助先进的热力学建模方法，可基于地质相关的温度、压力范围及组成变量（如pH值），评估各类有机反应的热力学可行性。然而，能够支撑多样有机化合物及环境条件建模的相关数据仍较为匮乏，且极少通过实验验证，针对有机氮化合物的相关研究更是如此。本研究构建了一套可估算常温常压下热力学性质的框架，随后可将该框架外推至不同温压范围，用于计算含直链烷基链与苄基官能团的水相伯胺、仲胺、叔胺及质子化胺（aminiums，即质子化胺类）的热力学性质。我们还开展了涉及甲胺类反应的水热实验（250℃、约40巴），以验证所构建的热力学模型；同时将其他烷基胺与苄基胺的模型预测结果与文献中已有的实验实测值进行对比。具体而言，我们结合现有热力学数据与常温常压下的估算值，搭配多种基于修正版Helgeson-Kirkham-Flowers状态方程（HKF状态方程）的现有外推方法，生成了与温压相关的酸解离常数（即pKa值）预测结果，该结果与此前的实验实测值高度吻合。我们采用相似方法，对伯胺/仲胺/叔胺/质子化胺、氨/铵盐及其对应醇类参与的反应进行产物分布预测，此类反应的整体产物分布取决于可逆取代反应过程。我们的预测结果与甲胺反应体系的实验结果、以及此前苄基胺反应体系的实验结果均吻合良好；针对该苄基胺反应体系，我们还完成了涉及苄醇的热力学估算。独立理论预测与实验实测结果之间的良好吻合性表明，我们估算的热力学性质可用于模拟其他不同温压范围的实验及天然水相体系中的胺类化学过程，为行星探测领域提供了新的研究工具。