主题：为什么碳正离子上给电子基团越多位移值反而升高？

原文由 degeangel 发表:
比如三甲基取代碳正离子就比二甲基取代的位移值高？

原文由 instrueagle 发表:
I assume you are talking about the carbon spectrum. When the number of methyl groups increases, the electron claud around the carbon of interest becomes denser, which forms chemical shielding, thus it needs higher magnetic power for its resonance (that is, its chemical shift becomes higher).

原文由 instrueagle 发表:
In this equaiton: B=B0(1-delta), delta is the shielding factor, if delta increases (meaning the shielding gets higher), the magnetic field strength the nucleus "feels" is lower, that is the chemical shift is higher.In a normal Fourier Transformation NMR spectrum, the chemical shift increases from the right hand side to the left.

原文由 degeangel 发表:
比如三甲基取代碳正离子就比二甲基取代的位移值高？

原文由 instrueagle 发表:
In this equaiton: B=B0(1-delta), delta is the shielding factor, if delta increases (meaning the shielding gets higher), the magnetic field strength the nucleus "feels" is lower, that is the chemical shift is higher.In a normal Fourier Transformation NMR spectrum, the chemical shift increases from the right hand side to the left.