Bond distances liquids

The [S2N]+ cation is an important reagent in S-N chemistry,63 especially in thermally allowed cycloaddition reactions with organic nitriles and alkynes, which give quantitative yields of heterocyclic cations (Scheme 3). It is conveniently prepared by reaction of S3N2C12 with AsF5 and S8 in liquid S02.63b The [SNS]+ cation is linear with S-N bond distances in the range indicating a bond order of two, i.e., S=N+=S. 

Various chlorine-substituted benzenes have been studied extensively by ED and MW and the most accurate results were obtained by joint analyses of ED intensities, rotational constants (from MW or high-resolution IR spectra) and dipolar coupling constants from liquid-crystal NMR spectra. Ab initio calculations have also been performed for some of these derivatives246 (Table 27). The primary interest in these studies is the degree of distortion of the benzene ring caused by chlorine substitution but in this context we will discuss only the variation of the C—Cl bond distances. In chlorobenzene this distance [173.90(23) pm] is very slightly longer than that in chloroethylene [173.0(4) pm], similar to the observation for C—F bonds. In the three disubstituted derivatives the C—Cl bond distances shorten only by a few tenths of a pm and are almost independent of the relative position of the two chlorines. These experimental results are reproduced correctly by the ab... 

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