Nuclear magnetic shielding substituent effects

E. Additivity of Substituent Effects in Nuclear Magnetic Shielding... 

Gutowsky, H.S., McCall, D.W., McGarvey, B.R. and Meyer, L.H. (1952). Electron Distribution in Molecules. I. F Nuclear Magnetic Shielding and Substituent Effects in Some Benzene Derivatives. J.Am.Chem.Soc., 74,4809-4817. 

Nuclear Magnetic Resonance. A definitive review of interproton allylic spin-spin coupling has been made which contains much of relevance to alicyclic systems. Study of the n.m.r. spectra of 36 axially and equatorially substituted cyclo-hexanols has identified some unexpected chemical shift effects. Substituent-dependent additive shielding increments were used successfully to calculate the chemical shift of methine H atoms present, so confirming the observation of some axial H atom shifts at lower fields than the equatorial H atom resonances, i.e. an inversion of the accepted behaviour. 

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