Bond lengths halides

The haloethanes all have similar rotational barriers of 3.2-3.7 kcal/mol. The increase in the barrier height relative to ethane is probably due to a van der Waals rqjulsive efiect. The heavier halogens have larger van der Waals radii, but this is ofiset by the longer bond lengths, so that the net efiect is a relatively constant rotational barrier for each of the ethyl halides. 

The formation of acyl halide-Lewis acid complexes have been observed by several methods. For example, both 1 1 and 1 2 complexes of acetyl chloride, with AICI3 can be observed by NMR spectroscopy. The existence of acylium ions has been demonstrated by X-ray diffraction studies on crystalline salts. For example, crystal structure determinations have been reported for /i-methylphenylacylium and acetylium ions as SbFg salts. There is also a good deal of evidence from NMR measurements which demonstrates that acylium ions can exist in nonnucleophilic solvents. " The positive charge on acylium ions is delocalized onto the oxygen atom. This delocalization is demonstrated in particular by the short O—C bond lengths in acylium ions, which imply a major contribution from the structure having a triple bond ... 

Bond lengths (Continued) carbonyl complexes dioxygen complexes disulphur complexes dithiocarbamates Mlerene complexes halide complexes halides... 

TABLE 1. Bond lengths (rg) and bond angles (ra) of thionyl halides from electron diffraction... 

Sulfone molecular structures, including sulfuryl halides, have been repeatedly reviewed through the late seventies28 and early eighties5. Scheme 1 contains a list of the compounds discussed in these references. While the structures of these compounds will be discussed, recent structural information that was not included in the above compilations will be described initially. The relevant substances are listed in Table 3 along with the S=0 bond lengths and OSO bond angles. 

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