Long Range Phenomena. IV (¹): The PMR‐spectra of 2‐halo‐3, 3, 5, 5‐tetramethyl‐cyclohexanone. Long range couplings not following “M” patterns

Abstract

Abstract Double irradiation experiments and solvent dependence studies prove that “non‐classical” long range phenomena occur, i.e. 4 J 2 e . 6 a , 4 J 2 e , 4 a , 4 J 4 a , 6 a (I a and II a ); 4 J 2 a , 6 e , 4 J 4 a , 6 a (I b and II b ). The criterion of the “Meinwald” disposition in assigning the nature of protons involved in long range coupling must be used with extreme care. In DMSO‐ d 6 4 J 4 a , 6 a for I b is more than twice the “classical” 4 J 4 e , 6 e coupling value, the former coupling not occurring across an sp 2 hybridized atom. Even small solvent changes influence long range couplings. Thus for I a no 4 J 2 e , 4 a is observed in chloroform, but it is 0.7 cps in carbon tetrachloride.