Structural Changes from Heating Amber and Copal as Observed by Nuclear Magnetic Resonance Spectroscopy,Magnetic Resonance in Chemistry

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Structural Changes from Heating Amber and Copal as Observed by Nuclear Magnetic Resonance Spectroscopy
Magnetic Resonance in Chemistry ( IF 1.9 ) Pub Date : 2020-01-29 , DOI: 10.1002/mrc.4992
Joseph B Lambert ₁ , Truongan V Nguyen ₁ , Allison J Levy ₁ , Yuyang Wu ₂ , Jorge A Santiago-Blay ₃

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Structural changes caused by heating of fossilized (amber) and semi-fossilized (copal) resins have been examined by nuclear magnetic resonance (NMR) spectroscopy. A set of 28 samples was constituted to include different geographical sources, degrees of maturation, colors, and structural groupings. The onset of structural alterations was determined by observation of the lowest temperature at which spectral changes occurred. Both proton spectra in solution and carbon-13 spectra in the solid state then were recorded of cooled samples after heating for 12 h at temperature increments, until liquification of the sample began. The spectra of both nuclides exhibit loss of a few peaks, broadening of most peaks, and enhancement of the unsaturated or aromatic region at the expense of saturated resonances. Such changes are irreversible and lead to a harder and less soluble material on cooling. The changes parallel those that occur with maturation of fossil resins or materials that lead to coal.

中文翻译：

通过核磁共振光谱观察到加热琥珀和 Copal 的结构变化

已通过核磁共振 (NMR) 光谱检查了由化石（琥珀色）和半化石（柯巴）树脂加热引起的结构变化。组成了一组 28 个样本，包括不同的地理来源、成熟度、颜色和结构分组。通过观察发生光谱变化的最低温度来确定结构改变的开始。然后在以温度增量加热 12 小时后记录冷却样品的溶液中的质子光谱和固态中的碳 13 光谱，直到样品开始液化。两种核素的光谱都表现出一些峰的损失，大多数峰的展宽，以及以饱和共振为代价的不饱和或芳族区域的增强。这种变化是不可逆的，冷却时会导致材料变硬且溶解度较低。这些变化与化石树脂或导致煤炭的材料成熟时发生的变化相似。

更新日期：2020-01-29

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