Infrared hole burning of crown ether 18-c-6 ammonium ion complexes.

Crystals of the complexes of 18-crown-6 with a number of ammonium salts (bromide, chloride, two forms of iodide, nitrate) and with amminetrifluoroboron have been prepared, analyzed with X-ray diffraction, and then investigated by infrared hole burning. The complexes all have similar hydrogen-bonding arrangements between the crown ether ring and the ammonium nitrogen. Hole burning of the infrared bands at low temperature identifies the N-D hydrogen bonds of the compounds that have been doped with a small amount of deuterium.

Infrared hole burning and conformational change in a borane-ammonia complex.

The N-D stretching region in the infrared spectrum of the ammonia complex of tris-(2-methoxymethyl-phenol)-borane containing one D atom has been examined. The N-D bands have been hole burned, and the resulting spectra reveal the reorientation kinetics of the ammonia. The ammonia is hydrogen bonded with the bond distances and reorientation barrier typical of other compounds.

Normal mode analyses of methyl palmitate all-trans and disordered forms in wagging progressive region.

Normal mode analyses are made for methyl palmitate molecule having all-trans or conformational disorders around the ester head group, in order to explain characteristic observed frequency shifts in the wagging progressive region between all-trans and disorder chains in triglyceride molecules. It was found that one gauche conformation at C(alpha)-C(beta) position and 90 degrees rotation of the ester head group in an alkyl chain produce frequency shifts for twisting mode as observed. For wagging modes, contamination of the disorders around the head group makes assignments change and apparent frequency shifts occur.