Nuclear magnetic double-resonance studies of organo-selenium compounds

1 H–{77Se} Double-resonance experiments have been used to determine selenium chemical shifts in 80 organoselenium compounds containing 77Se in natural abundance. The shifts cover a range of over 1500 p.p.m. and are relatively insensitive to solvent effects. Electronegative substituents give shifts to low field, and in general the shifts parallel those found in similar phosphorus compounds, but are several times larger for a given electronic change. Correlations are found with the extent of α-chain branching in alkyl derivatives, and with Hammett σ-constants in substituted aryl derivatives. The chemical shifts show greater promise as diagnostic tools than do coupling constants involving selenium.