In this work, 2-fluoro-benzamide (l), 2-fluoro-Nmethylbenzamide (2) and 2-fluoro-N,N-dimethylbenzamide (3) were chosen as model compounds in which to study long-range through-space couplings. In both 1 and 2 there should be strong intramolecular F-H bonds which would constitute eficient routes for transmitting nuclear spin information between the F atom and those of the amide moiety. The comparison of such couplings with those observed in the tertiary amide 3 can yield information about the transmission mechanisms that will help to define such couplings.* Author to whom correspondence should be addressed. It is also expected that different solvents would affect the coupling pathway without actually breaking the intramolecular hydrogen bond. There are strong intramolecular hydrogen bonds in o-salicylaldehyde derivatives' 2,1 and o-nitrophenol derivatives,'" for which it has been shown that a polar solvent increases the rapid exchange rate of the hydroxyl proton and destroys spin-spin c o u p h g associated with the OH, but the side-chain conformation remains adequate for intramolecular hydrogen bonding to take place. Traces of water, even in solvents of low polarity, can produce these effects.'" For this reason, side-chain parameters in 2 were also measured in four different solvents and the variations observed for both coupling constants and

Proximity effects on lJ(CH) couplings are studied from a theoretical point of view in the following systems:CH4/FH (A) and H*O/HCN (B) which form dimers by hydrogen-bond interactions. 'J(CH) couplings for different intermolecular distances are calculated for the C-H bond facing the atom bearing lone pairs. While in the former system, this coupling is increased owing to the proximity to the F atom; in the latter this coupling is decreased owing to the proximity to the 0 atom. These opposite trends are accompanied by slight shortening and lengthening, respectively, of the corresponding C-H bond lengths. As part of this work, measurements of 'J(CH) couplings in 9 4 1,3-dioxolan-2-y1)-1,2,3,4-tetrafluorotriptycene (I) and l-formyl-2-hydroxy-8-fluoronaphthalene (11) and J ( N H ) in o-fluorobenzamide (III), showing proximity effects as those described above are carried out. These results suggest that J(XH) couplings are adequate probes to distinguish two different types of X-H.-Y hydrogen bonds.

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The organomercury compounds HgR2 (R = 2‐Cl,6‐FC6H3, 2,6‐F2C6H3, 2,3,6‐F3C6H2, m‐HC6F4, p‐HC6F4, or C6F5) and RHg(O2CR) (R = 2‐Cl,6‐C6H3, 2,6‐F2C6H3 or 2,3,6‐F3C6H2) have been obtained in moderate – good and low yields respectively from decarboxylation reactions of the corresponding mercury(II) fluorobenzoates in boiling pyridine. By contrast, mercury(II) 2,3,4‐5‐tetrafluorobenzoate gave a low yield of CO2, a trace of Hg(o‐HC6F4)2 and a very low yield of o‐HC6F4Hg(O2CC6F4H‐o). The 199Hg NMR spectra of the diorganomercurials (R = 2‐Cl,6‐FC6H3, 2,6‐F2C6H3, 2,3,6‐F3C6H2, 2,4,6‐F3C6H2, 2,6‐Cl2C6H3, o‐HC6F4, m‐HC6F4, p‐HC6F4 or C6F5) are discussed.

The details of two‐dimensional 13C1H correlated spectra have provided information about the relative signs of J(C, F) and J(F, H) for several molecules in which C, F and H are mutually coupled. Unlike signs are found for J(C, F) and J(F, H) when the coupling pathways lie approximately in the plane, but serious deviations from planarity can bring about changes in sign of J(F, H) and J(C, F).