Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 10—Carbocages

Abstract

A comprehensive theoretical study of nine classical caged polycycloalkanes (tetrahedrane, prismane, homoprismane, quadricyclane, cubane, pentaprismane, hexaprismane, adamantane and diamantane) was carried out with special focus on the structural behavior of their J(C,C) values calculated at the SOPPA level. The structural behavior of J(C,C) in small carbocages is dominated by steric strain whereas in medium-sized polycycloalkanes the J(C,C) values show no marked peculiarities and follow several well-defined structural trends typical of other alicyclic compounds.

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 8—Monocycloalkanes

“…113 The same effect was manifested later for carbon-carbon bonds (n - In the pioneering paper by Perlin and Casu, 116 it was found that the axial one-bond carbon-hydrogen couplings in the six-membered saturated heterocycles are dramatically smaller (by ca 10 Hz) than those of the equatorial C-H bonds adjacent to either oxygen or nitrogen of the ring, and this was attributed 117 to the hyperconjugative n -Ł C -H interaction involving the antibonding orbital of the axial C-H bond and the heteroatom lone pair (see also reviews 118 and references cited therein). In the same manner, the smaller value of 1 (C,H), the numerical magnitude of the Perlin effect experimentally measured for cyclohexane of ca 4 Hz 93 is well reproduced in the present study by both SOPPA and SOPPA(CCSD) calculations, being ca 5-7 Hz in cyclobutane (2), cyclopentane (3) and cyclohexane (4) and much less (ca 1-2 Hz) in cycloheptane (5) and cyclooctane (6).…”

“…111 The only welldefined example of the pronounced medium effects in the values of J(C,C) was found in acetylene. The latter constant was measured recently with ultrahigh experimental accuracy by Chertkov in acetone-d 6 liquid phase (166.010 š 0.004 Hz), cited as a personal communication by Wigglesworth et al,32d and also by Jackowski et al 99 in dilute xenon gaseous solution (174.78 š 0.02 Hz). The former (166.01 Hz) seems to be surprisingly small and the latter (174.78 Hz) seems to be surprisingly large compared with the originally reported value of 171.5 Hz measured in CCl 4 liquid phase.…”

“…All basis sets used in this study with DALTON either were taken from the Dalton Basis Sets Library as they are or were slightly modified by adding or removing polarization, core, tight or diffuse functions or decontracting their s-parts as specified in previous papers. 5,6 These basis sets together with some other closely related ones are specified in Table 6.…”

“…88 We restricted ourselves to the predominant conformations, namely planar eclipsed cyclopropane (1), bent cyclobutane (2), envelope cyclopentane (3), chair cyclohexane (4), twist-chair cycloheptane (5) and boat-chair cyclooctane (6). All conformations were verified as stationary points corresponding to global minima without imaginary frequencies, as confirmed by harmonic vibrational frequencies analysis in each particular case.…”

“…Seven previous publications in this series devoted to threemembered rings, 1 strained polycycloalkanes, 2 polyhedranes, 3 bicycloalkanes, 4 bridged bicycloalkanes, 5 propellanes 6 and spiroalkanes 7 of up to 14 carbon atoms manifested a real breakthrough of ab initio methods based on the general SOPPA (Second-Order Polarization Propagator Approach) formalism 8,9 to calculate spin-spin coupling constants into the area of organic chemistry. The unprecedented reliability of SOPPA to calculate one-bond and long-range spin-spin coupling constants J(C,C), J(C,H) and J(H,H) in a wide range of carbocyclic compounds has been manifested, however, leaving apart the classical series of monocycloalkanes.…”