Sulphonamidyl radicals

The spectra of some representative sulphonamidyl radicals are shown in Figure 3. Notable features of the spectra are (a) the coupling to the 14N nucleus, which gives rise to the 1 1 1 triplet pattern most obvious in Figure 3a, b, (b) the coupling to the fi-CH protons in the AT-alkyl and N-alkoxy radicals (Figure 3a, b, c), (c) the coupling to the AT-aryl but not... 

A corresponding solid-state study for a sulphonamidyl radical would be appropriate, but it seems reasonable to assume that such radicals adopt a structure not too dissimilar from 03SNH. Certainly, the ab initio calculations for MeS02NHMe indicate that a nN configuration in which the N—C bond subtends an angle of ca 120° to the S—N bond is the most stable. This corresponds nicely with the structure 11. Experimentally, the question as to whether sulphonamidyl radicals adopt the bent structure 12 or the linear structure 13 and 14 is resolved by comparison of the data for acyclic and cyclic radicals. The nitrogen hyperfine couplings for these types of radical are so similar that it can be concluded that both adopt the bent structure 12. 

N-[(/-Butylsulphinyl)oxy] sulphonamides (59) rearrange with N—O cleavage via sulphonamidyl radicals 60 to give 61 in ca 20% yield in a radical cage recombination process, along with products formed after escape from the cage (equation 36)162. 

A detailed study by ESR of the arenesulphonyl radicals 1 has been reported following the irradiation of the corresponding chlorides in toluene9. The spin distribution in the radicals was determined as was the rotation around the S—C aryl bond. A similar study was performed using the sulphonamidyl chlorides 2. This clearly showed that the radical was still sulphur-centred and that there was little interaction with the adjacent nitrogen10. A review of the reactivity and the formation of sulphur-centred radicals has been published11. 

Physical Properties. - The E.S.R. spectra of sulphonamidyl (26) and nitroxide (27 R Me,Bu, ,cyclopentyl) radicals were recorded and analysed. The N and (J hyperfine splitting constants of both [and 2 other sulphonamidyls] were in agreement with a n/N electronic ground state including a planar geometry around the N radical centre. The possible geometries around nitroxide N and further conformational implications were discussed. ... 

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