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1-Norbornyl cation may be in equilibrium with 2-norbornyl cation
Progress in Reaction Kinetics and Mechanism ( IF 2.1 ) Pub Date : 2019-08-22 , DOI: 10.1177/1468678319861319
Andrew Mamantov 1
Affiliation  

New 1H and 13C NMR 400 MHZ spectra of the 2-Nb cation under stable ion conditions, for example, in SbF5/SO2F2/SO2ClF, −80 oC, show besides the usual 1H NMR resonances at δ 4.93, 2.82, 1.85, the never before seen singlet, δ 9.63, and doublet, δ 2.97 (J2,6 = 16.6 Hz), ratio 1.00 : 1.07, proposed to be due to resonance-stabilized bridgehead 1-Nb cationic enantiomers in equilibrium with 2-Nb cation. The corresponding 13C proton-coupled NMR spectrum, −80 oC, has a C3,5,7 triplet, δ 30.45, J(CH) = 139.14 Hz, and C4 doublet, δ 37.7, J(CH) = 154.54 Hz. The C1,2,6 absorption, δ 91.04 is relatively broad, whereas previously, at −70 oC, it was a pentuplet. The 13C proton-decoupled spectrum at −80 oC shows the C4 doublet and C3,5,7 triplet collapsed to a singlet, but the C1,2,6 resonance is still broad. Analyses support the slowing exchange between resonance stabilized enantiomeric 2-cations at ≤ –159 oC. Some future studies are proposed.

中文翻译:

1-降冰片基阳离子可能与 2-降冰片基阳离子处于平衡状态

2-Nb 阳离子在稳定离子条件下的新 1H 和 13C NMR 400 MHZ 光谱,例如,在 SbF5/SO2F2/SO2ClF,-80 oC 中,显示除了通常在 δ 4.93、2.82、1.85 处的 1H NMR 共振之外,之前看到的单峰 δ 9.63 和双峰 δ 2.97 (J2,6 = 16.6 Hz),比率为 1.00:1.07,推测是由于共振稳定的桥头 1-Nb 阳离子对映异构体与 2-Nb 阳离子平衡。相应的 13C 质子耦合 NMR 光谱 -80 oC,具有 C3,5,7 三重峰,δ 30.45,J(CH) = 139.14 Hz,和 C4 双峰,δ 37.7,J(CH) = 154.54 Hz。C1,2,6 吸收,δ 91.04 相对较宽,而以前,在 -70 oC 时,它是五重峰。-80 oC 下的 13C 质子解耦光谱显示 C4 双峰和 C3、5、7 三重峰塌陷为单峰,但 C1、2、6 共振仍然很宽。分析支持在 ≤ –159 oC 时共振稳定的对映体 2 阳离子之间的交换减慢。提出了一些未来的研究。
更新日期:2019-08-22
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