Stoichiometric and Non-Stoichiometric Hydrates of Brucine.
Stoichiometric and Non-Stoichiometric Hydrates of Brucine.
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DOI：
10.1021/acs.cgd.6b01231
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发表时间：
2016-10-05
影响因子：
3.8
通讯作者：
Griesser UJ
中科院分区：
文献类型：
--
作者：
Braun DE;Griesser UJ
阐明了温度和水活度(aw)/相对湿度（RH）对三种水合物（HyA、HyB和HyC）、等结构脱水（HyAdehy）、无水（AH）和无定形马钱子碱的固相稳定性和转化途径的复杂相互作用，并量化了转化焓。在25℃条件下，当相对湿度< 40%时，二水合物（HyA）表现出非化学计量（脱）水化行为，并且水分子的去除导致了同形脱水结构。亚稳态脱水产物在最干燥的条件下储存时转化为氢氧化钠，如果暴露于水分则转化为氢氧化钠。HyB是一种化学计量的四水合物。水分子的损失导致HyB坍缩成无定形相。无定形马钱子碱在RH < 40% RH时转化为水合相，在较高RH值时转化为水合相的混合物。第三种水合物（HyC）在25℃时RH≥55%时才稳定，含有3.65-3.85 mol当量的水。在25℃或加热条件下，在RH < 55%条件下一步脱水，得到AH。在25℃RH < 40%时，AH是马钱子碱热力学最稳定的相。根据条件、温度和能量的不同，这三种水合物中的每一种都成为热力学上最稳定的形式。这项研究证明了应用互补分析技术和适当的方法来理解具有多种水合物的化合物的固体形态之间的稳定范围和转变行为的重要性。利用互补分析技术揭示了温度和水活度/相对湿度对实际相关形式的马钱子碱固体形态稳定性和转化途径的复杂相互作用。根据不同的环境条件，三水合物（化学计量和非化学计量）或无水马钱子碱可能成为热力学上最稳定的形式。测定了固体形态之间的转变焓。
The complex interplay of temperature and water activity (aw)/relative humidity (RH) on the solid form stability and transformation pathways of three hydrates (HyA, HyB, and HyC), an isostructural dehydrate (HyAdehy), an anhydrate (AH), and amorphous brucine has been elucidated and the transformation enthalpies quantified. The dihydrate (HyA) shows a nonstoichiometric (de)hydration behavior at RH < 40% at 25 °C, and the removal of the water molecules results in an isomorphic dehydrate structure. The metastable dehydration product converts to AH upon storage at the driest conditions or to HyA if exposed to moisture. HyB is a stoichiometric tetrahydrate. The loss of the water molecules causes HyB to collapse to an amorphous phase. Amorphous brucine transforms to AH at RH < 40% RH and a mixture of hydrated phases at higher RH values. The third hydrate (HyC) is only stable at RH ≥ 55% at 25 °C and contains 3.65–3.85 mol equiv of water. Dehydration of HyC occurs in one step at RH < 55% at 25 °C or upon heating, and AH is obtained. The AH is the thermodynamically most stable phase of brucine at RH < 40% at 25 °C. Depending on the conditions, temperature, and aw, each of the three hydrates becomes the thermodynamically most stable form. This study demonstrates the importance of applying complementary analytical techniques and appropriate approaches for understanding the stability ranges and transition behavior between the solid forms of compounds with multiple hydrates. Complementary analytical techniques were applied to unravel the complex interplay of temperature and water activity/relative humidity on the solid form stability and transformation pathways of practically relevant forms of brucine. Depending on the environmental conditions, three hydrates (stoichiometric and nonstoichiometric) or anhydrous brucine may become the thermodynamically most stable form. The transformation enthalpies between the solid forms were determined.