Abstract:
Hydrogen bonding was studied for selected carbonyl and phosphoryl substrates using IR and Raman spectroscopic techniques. IR spectroscopy was found to be the more effective and generally applicable technique. The formation constants obtained for the carbonyl group were in good agreement with the literature values, irrespective of whether the values of 𝚫vc=o or 𝚫v0-H, were used for the calculations. For the phosphoryl substrates, the use of the 𝚫vP=o values led to low values for formation constants, and reliable values were only obtained by using the 𝚫v0-H(phenol) shifts. Hydrogen bonding was also studied in compounds containing two carbonyl [R-C(O)-CH2-C(O)-R'] and phosphoryl[R-P(O)-CH2-P(O)-R'] groups. The -P(O)-CH2-P(O)- system behaved like an arrangement of independent groups and hydrogen bonding was observed when phenol was added. The -C(O)-CH2-C(O)- function existed as an intramolecularly hydrogen bonded keto-enol system, which did not get involved in the external hydrogen bonding. For systems containing a phosphoryl as well as a carbonyl group[-C(O)-CH2-P(0)-0], the carbonyl group formed enolic systems, while the phosphoryl group formed ordinary hydrogen bonds upon addition of phenol.
