CHEM 2331H Chapter Notes -Photon, Coupling Constant, Free Induction Decay
Document Summary
Each proton assumes alpha/beta state: alpha is lower energy, so more alpha than beta spins, magnetic field strength energy difference btwn 2 spin states . , where e = energy difference btwn 2 states, h = planck"s: eqn: e= h. @ certain frequency: beffective = bexternal bshielding (so need to have greater external field if want resonance, protons in different chemical environments shielded by different amts not in resonance. Determine value relative to reference compound added to sample. Magnetic field strength difference btwn sample proton resonances and reference proton resonances can be measured very accurately: most common reference compound = tetramethylsilane (ch3)4si (tms) Silicon = less electronegative than c tms methyl groups = relatively electron rich well-shielded protons. Tms protons absorb @ higher field strength than most h"s bonded to. Nmr spectrometers: most common chem. shift scale = (delta) scale. Tms signal = defined as 0. 00ppm on the scale. Aromatic protons = strongly deshielded large chemical shift.
