The variable oxygen probe has been applied to axial and equatorial 4-pyranols 4 and 5 and their ester and ether derivatives. Plots of C–OR bond distance versus pK_a (ROH) provided evidence for slightly stronger donation into the σ*_C–OR antibonding orbital in the equatorial derivatives 5 than in the axial derivatives 4, which is consistent with the presence of a through-bond n_O–σ_CC–σ*_CO interaction in 5. Evidence in support of this interpretation was also provided by density functional theory (DFT) calculations and natural bond orbital (NBO) analyses of the various orbital interactions in the 4-pyranols 4 and 5, their protonated analogues 4·H₂O⁺ and 5·H₂O⁺, and the corresponding cyclohexane derivatives 6, 7, 6·H₂O⁺, and 7·H₂O⁺.

可变氧探针已应用于轴向和赤道的4-吡喃醇4和5及其酯和醚衍生物。C–OR键距与p K _a（ROH）的关系图为赤道导数5的σ* _C–OR反键轨道比轴向导数4的捐赠稍强提供了证据，这与存在贯通-键ñ _ø -σ _CC -σ* _CO在相互作用5。密度泛函理论（DFT）计算和对4吡喃酚4和5，其质子化类似物4 ·H ₂ O ⁺和5的各种轨道相互作用的自然键轨道（NBO）分析也提供了支持这种解释的证据。·H ₂ ö ⁺，和相应的环己烷衍生物6，7，6 ·H ₂ ö ⁺，和7 ·H ₂ ö ⁺。