Experimental and theoretical study of substituent effects on3J(13C1-1H) coupling constants in 1-X-bicyclo[1.1.1]pentanes

Abstract

A series of 23 bridgehead-substituted bicyclo[l.l.l]pentanes were synthesized and the 3J(Cl-H) coupling constants determined from their proton-coupled I3C NMR spectra. It was found that the values of the couplings are strongly dependent upon the type of substituent present, with powerful effects exerted by the halogens in particular. The IPPP-CLOPPA-INDO theoretical approach, which was employed to provide a measure of the extent of through-bond versus through-space transmission of coupling information, was found to give 3J(Cl-H) values in good agreement with experimental data. Empirical substituent parameter regressions were performed and found to be consistent with the CLOPPA description of the increase in both the through-bond and through-space contributions to the coupling. The substituent parameter regressional analyses also demonstrated that electronegativity effects play a predominant role in determining the magnitude of the couplings, particularly in those substrates in which the substituent is attached to the ring system by a secondrow element.

Partially Bridge-Fluorinated Dimethyl Bicyclo[1.1.1]pentane-1,3-dicarboxylates: Preparation and NMR Spectra

“…Comparison of Observed and Calculated Spin − Spin Coupling Constants. Bicyclo[1.1.1]pentane 7 has been previously recognized as an especially intriguing challenge to the theory of spin−spin coupling in molecules, , and it has been noted that the calculated magnitudes of coupling constants depend strongly on the size of the basis set used . As usual, the Fermi contact (FC) term was found to be dominant for 1 H− 1 H coupling …”

Experimental and Theoretical Study of Hyperconjugative Interaction Effects on NMR 1JCH Scalar Couplings

“…In Ib the similar 13 C 1 −SCS are slightly increased in comparison with those of Ia . It is also known that in series Ia unusual substituent effects on 3 J C 1 H SSCCs were observed, and they were correlated with the strong changes on delocalization interactions induced by an X substituent …”

“…Experimental Details. Syntheses of compounds of series Ia and Ib are described elsewhere. , Samples were prepared in CDCl 3 (X = NH 3 Cl in D 2 O) at concentrations of ca. 0.6 mol/L.…”

Strained‐Ring Compounds Containing Nitro Groups as Potential Explosive Materials

“…We also tried to obtain the lattice enthalpy of formation of mono‐nitrated spiro and bicyclo compounds. The enthalpy of sublimation of S1 and B1 was estimatd as 605.5 and 589.7 kcal/mol according to the literature . Because the sublimation enthalpy was estimated from the Troutons's rule, the enthalpy of formation for solid S1 and B1 can be obtained as Δ H f o = 589.9 and 573.2 kcal/mol.…”