An endocyclic restriction test for acid-catalyzed transfer of chlorine from a protonated chloroamine to an aromatic ring provides data that are consistent with a transition structure with a large bond angle between the entering and leaving groups around chlorine. These results rule out a dissociative mechanism or a mechanism that has an oblique angle between the entering and leaving groups.
The trajectories for nucleophilic substitutions at sulfur(VI) and sulfur(II) have been investigated by the endocyclic restriction test. On the basis of double-labeling experiments, the sulfur(VI) transfer in the conversion of 1 to 2 is found to be intramolecular, while the sulfur(VI) transfer in the conversion of 3 to 4 and the sulfur(II) transfer in the conversion of 5 to 6 are found to be intermolecular. These results are taken to be consistent with transition structures for these sulfur transfer reactions which require a large angle between the entering and leaving group, a geometry analogous to apical group positions in trigonal bipyramidal transition states.
A series of nine 17 O labeled triarylphosphine oxides [(pwas synthesized, 17 O NMR spectroscopic studies were carried out (toluene solvent / 95 °C and CDCI3 / 60 °C) and the spectrum was fit with two Lorentzian peaks. The chemical shifts range from 5 51.8 to 55.7 in toluene and 8 44.8 to 48.9 in CDCI3, while ^p o varies from 159.6 to 168.6 Hz in toluene. The data were fit to the Taft DSP and Hammett equations and related to other NMR parameters for this system and the analogous X 5 -phosphazenes [(p-R-C6H 4 ) 3 PNPh]. Using the Taft DSP equation the 17 O substituent chemical shifts gave pj and p R with opposite signs which is different from what is observed with the X 5 -phosphazenes. VpQ. on the other hand correlates best with the Hammett a+ constants. The data are consistent with a triple bond contribution to the PO bonding.
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