Proton chemical shifts in saturated hydrocarbons

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Abstract
The proton chemical shifts of a number of relatively unstrained hydrocarbons have been analysed in terms of the local diamagnetic shielding and long-range shielding by carbon-carbon single bonds. The analysis suggests that the latter term is the dominant factor determining the relative chemical shifts, the most probable value of ΔX CC being near 7 × 10-30 cm3 molecule-1. The relative shifts of the methyl and methine protons of meso and dl 2, 3-disubstituted butanes and axial and equatorial methyl groups in cyclohexane rings are discussed in relation to this value of ΔX CC.