期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 118, 期 31, 页码 6068-6077出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp411810y
关键词
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资金
- Carnegie DOE Alliance Center (CDAC) [DE-NA002006]
- DOE-NNSA [DE-NA0001974]
- DOE-BES [DE-FG0299ER45775, DE-AC02-06CH11357]
- NSF
- GSECARS through NSF Grant [EAR-1128799]
- DOE Grant [DE-FG02-94ER14466]
The structural phase stability of N-(4-hydroxyphenyl) acetamide (paracetamol) has been studied at ambient temperature up to 23 GPa using Raman spectroscopy. Spectral changes have provided further evidence for a highly kinetically driven Form I -> II transition that occurs as a mixed phase from 4.8 to 6.5 GPa, and might complete as early as 7 GPa. Upon further compression to 8.1 GPa, a drastic shift in spectral signature was observed providing the first evidence for a previously undiscovered Form IV of paracetamol. Additional shifts in mode intensities were observed near 11 GPa indicating a potential restructuring of the hydrogen bonding network and/or structural modification to a potentially new Form V. Phase boundaries at 7 and 8 GPa were confirmed under hydrostatic conditions using Raman spectroscopy. Spectral changes indicate that the transition Form IV -> V occurs near 11 GPa. Multiple ab initio harmonic frequency calculations at different levels of theory were performed with a B3LYP/6-31G** being used to provide a more robust mode assignment to our experimentally obtained Raman modes. High pressure X-ray diffraction (XRD) was performed up to 21 GPa, which provided further evidence for a highly kinetically driven Form I -> II transition in agreement with our Raman measurements. In addition, the XRD provided further evidence for the existence of Form IV near 8 GPa and Form V near 11 GPa with Form V persisting up to 21 GPa.
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