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Study on conformation interconversion of 3-alkyl-4-acetyl-3,4-dihydro-2H-1,4-benzoxazines from dynamic NMR experiments and ab initio density functional calculations
Yang, G; Han, XW; Zhang, WP; Liu, XM; Yang, PY; Zhou, YG; Bao, XH
刊名JOURNAL OF PHYSICAL CHEMISTRY B
2005-10-06
DOI10.1021/jp050874d
109期:39页:18690-18698
收录类别SCI
文章类型Article
WOS标题词Science & Technology ; Physical Sciences
类目[WOS]Chemistry, Physical
研究领域[WOS]Chemistry
关键词[WOS]POLARIZABLE CONTINUUM MODEL ; MOLECULES ; EXCHANGE
英文摘要Variable-temperature NMR experiments and ab initio density functional calculations were carried out to investigate the conformation interconversion of novel chiral 3-alkyl-3,4-dihydro-2H-benzo[1,4]oxazine derivatives. With CDCl3 as the solvent, the coalescence temperatures of H-2, H-3, H-11 and H-19 of product 1 are about 289, 304, 292, and 316 K, with the corresponding activation free energies at 58.0 +/- 6.7, 60.9 +/- 7.1, 58.3 +/- 6.8, and 59.6 +/- 6.9 kJ(.)mol(-1), respectively. When dimethyl sulfoxide (DMSO-d(6)) was used as the solvent, H-1 and C-13 NMR signals were completely assigned at 375 K. The effects of solvent and temperature were investigated through a polarizable continuum model. At each theoretical level (MP2 or B3LYP), the changing tendencies of the calculated activation free energies and interconversion rates agree well with those of the NMR results. In addition, the interconversion rate at each specified temperature was calculated to be about 1.5 times faster in DMSO-d6 than in CDCl3. Accordingly, we failed to observe the coalescence phenomena of H-3 and H-19 in DMSO-d(6) by NMR measurements from 296 to 375 K. The substitution effect at the R-1-R-5 positions was considered using density functional calculations, with the activation barriers decreasing as follows: product 6 > 3 > 1 > 7 > 2. This sequence is consistent with that of the reaction heats, except for product 7, implying that the interconversion processes may be thermodynamically controlled. Surprisingly, the substituted groups near the acetyl group in product 2 and 7 do not elevate the activation barrier but, instead, lower it somewhat, with the possible reasons for this provided in the paper.
语种英语
WOS记录号WOS:000232318500065
引用统计
文献类型期刊论文
条目标识符http://cas-ir.dicp.ac.cn/handle/321008/139930
专题中国科学院大连化学物理研究所
作者单位Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China
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GB/T 7714
Yang, G,Han, XW,Zhang, WP,et al. Study on conformation interconversion of 3-alkyl-4-acetyl-3,4-dihydro-2H-1,4-benzoxazines from dynamic NMR experiments and ab initio density functional calculations[J]. JOURNAL OF PHYSICAL CHEMISTRY B,2005,109(39):18690-18698.
APA Yang, G.,Han, XW.,Zhang, WP.,Liu, XM.,Yang, PY.,...&Bao, XH.(2005).Study on conformation interconversion of 3-alkyl-4-acetyl-3,4-dihydro-2H-1,4-benzoxazines from dynamic NMR experiments and ab initio density functional calculations.JOURNAL OF PHYSICAL CHEMISTRY B,109(39),18690-18698.
MLA Yang, G,et al."Study on conformation interconversion of 3-alkyl-4-acetyl-3,4-dihydro-2H-1,4-benzoxazines from dynamic NMR experiments and ab initio density functional calculations".JOURNAL OF PHYSICAL CHEMISTRY B 109.39(2005):18690-18698.
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