Proton chemical shifts of some halogenated steroids and t-butylcyclohexanes
The chemical shifts of protons α, β, and γ to the halogen atoms in 9α-halogeno-11β-hydroxyprogesterone, 2β-halogeno-3α-hydroxy-5α-cholestane, and trans-2-halogeno-trans-5-t-butylcyclohexanols have been measured in dilute carbon tetrachloride solutions. The chemical shifts of the α- and β-protons can be correlated with electronegativity after allowing for a calculated ‘C–C bond shift’. The chemical shift of the C(10)-methyl group, which is γ to the halogen atom in 9α-halogeno-11β-hydroxyprogesterone, appears to be controlled by increasing size of the substituent, unlike the γ protons in the 1-halogenoadamantane series with fixed stereochemistry which follows the order expected for electronegativity. The possibility that trans-2-halogeno-trans-5-t-butychyclohexanol may not exist in the true chair conformation is also discussed.