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Radicalization and Radical Catalysis of Biomass Sugars: Insights from First-principles Studies

机译：生物质糖的自由基化和自由基催化：来自第一性原理研究的见解

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Ab initio and density functional calculations are conducted to investigate the radicalization processes and radical catalysis of biomass sugars. Structural alterations due to radicalization generally focus on the radicalized sites, and radicalization affects H-bonds in D-fructofuranose more than in D-glucopyranose, potentially with outcome of new H-bonds. Performances of different functionals and basis sets are evaluated for all radicalization processes, and enthalpy changes and Gibbs free energies for these processes are presented with high accuracy, which can be referenced for subsequent experimental and theoretical studies. It shows that radicalization can be utilized for direct transformation of biomass sugars, and for each sugar, C rather than O sites are always preferred for radicalization, thus suggesting the possibility to activate C-H bonds of biomass sugars. Radical catalysis is further combined with Br?nsted acids, and it clearly states that functionalization fundamentally regulates the catalytic effects of biomass sugars. In presence of explicit water molecules, functionalization significantly affects the activation barriers and reaction energies of protonation rather than dehydration steps. Tertiary butyl and phenyl groups with large steric hindrances or hydroxyl and amino groups resulting in high stabilities for protonation products drive the protonation steps to occur facilely at ambient conditions.
机译：进行了从头算和密度函数计算，以研究生物质糖的自由基化过程和自由基催化作用。由于自由基化引起的结构改变通常集中在自由基位点上，并且相比于D-吡喃葡萄糖，自由基化对D-果糖呋喃糖中的氢键影响更大，可能与新的氢键有关。评估了所有自由基化过程的不同功能和基集的性能，并以高精度显示了这些过程的焓变和吉布斯自由能，可供以后的实验和理论研究参考。它表明自由基化可用于生物质糖的直接转化，并且对于每种糖，C而不是O位始终是自由基化的首选，因此表明激活生物质糖C-H键的可能性。自由基催化与布朗斯台德酸进一步结合，并且清楚地表明功能化从根本上调节了生物质糖的催化作用。在存在明显的水分子的情况下，功能化会显着影响质子化的活化壁垒和反应能，而不是脱水步骤。具有大的空间位阻的叔丁基和苯基或羟基和氨基导致质子化产物的高稳定性，驱动质子化步骤在环境条件下容易发生。

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