HYDROGEN-BONDING .64. IR STUDY OF HYDROGEN-BONDING IN TRI-I-PENTYLAMMONIUM HALIDES AND THEIR HYDRATES, FORMATION OF A MOLECULAR (I-C5H11)(3)NHF SPECIES, AND NMR-STUDY OF CONFORMATION OF TRI-I-PENTYLAMMONIUM ION IN SOLUTION

Tri-i-pentylammonium chloride and bromide form monohydrates which cont ain planar (H2O . X)(2) clusters; these clusters are sandwiched betwee n ammonium cations with N-H hydrogen bonds to each cluster X(-). The i odide fails to form any lower hydrate. ''Tri-i-pentylammonium fluoride '' is not a salt; rather the 1:1 adduct of HF and tri-i-pentylamine is a liquid molecular complex with a three-center covalent N-H-F bond. T his adduct is somewhat hygroscopic, but does not form a crystalline mo nohydrate. Fourier transform NMR spectra and molecular modeling demons trate that rotation is restricted about the alpha-CH2 to beta-CH2 sigm a-bonds of the cation in solution, with the R(3)N(+) group and i-propy l group in a trans arrangement about each bond. Modeling and considera tion of J values and splitting patterns suggest free rotation occurs a bout the beta-CH2 to gamma-CH sigma-bond, and that the delta-CH3 group s also rotate freely.