Hydrogen bond and proton transfer in complexes of trioctylamine with halogenoacetic acids

Proton Transfer to CpRuH(CO)(PCy3) Studied by Low-Temperature IR and NMR Spectroscopy

“…The corresponding ν OCO as vibration of the hydrogen‐bonded acetate in this complex is assigned to the new sharp band at 1710 cm −1 , which is located between the band of dimeric 2d and of the homoconjugated anion 6d . This assignment is in agreement with previous studies of molecular and ionic hydrogen‐bonded complexes of trifluoroacetic acid with organic and metal‐containing bases 34−38. Finally, before we discuss the spectral changes between spectra d, f, and g in Figure 3 we have to discuss the origin of the remaining two bands that are assigned to the CO ligand and trifluoroacetate group of 7d .…”

“…Therefore, we can now safely assign this new band to the free protonated ion 5 . Moreover, another new band arises at 1648 cm −1 , which we attribute to ν OCO as of the homoconjugated trifluoroacetate 34−38. The excess of the acid is demonstrated by the band at 1790 cm −1 .…”

Dielectric, acoustic, densimetric and viscosimetric investigations of the tributylamine + propionic acid system

“…In such mixtures, mainly 1 : 1 and 1 : 2 (amine : acid) complexes are formed.10h15 When the di †erence between pK a values of an acid and amine increases, the contribution of ionic forms of complexes, resulting from proton transfer, increases, too.16h19 In complexes where two or more acid molecules are involved the ionic form of hydrogen bonding seems to be preferred. 14,15 The possibility of proton transfer in OHÉ É ÉN complexes increases in solvents with a large dielectric constant, and depends considerably on the solvent proton-donor character.19h22 However, the properties of binary amineÈacid systems (without an additional solvent) are much less understood. The non-idealities mentioned above indicate complicated acidÈbase interactions, presumably leading to strong association of complexes as well as to formation of ions that are probably responsible for the increase in viscosity.2 In such systems, not only the existence of 1 : 1 and 1 : 2 complexes but larger associates have also been postulated.2,3, 23 The system under investigation, tributylamine ] propionic acid, has already been the subject of dielectric measurements.…”