Effects of H Bonding on Equilibria

Internal H bonding occurs in phosphoramidates of the type (13.30) and this can effect equilibria between amido and imidol forms (7.12). According to spectroscopic evidence, esters of trichloroacetylamidophosphoric acid exist as (13.31a) rather than (13.31b), which suggests that N-H-0=P bonds are more stable than N-H-0=C. 

Internal H bonding can influence equilibria and so determine solid state configuration. According to NMR data, dipivaloyl phosphine exists (like the carbon analogue) as an equilibrium between three structures (13.32a,b,c) but in the solid state a symmetrical molecule is stabilised by an internal H bond which forms the ring structure (13.32d). 

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