ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Thermochemical properties of cluster ions, involving Cl−, Br− and I− solvated by ammonia, were measured by using high-pressure mass spectrometry. Standard enthalpy changes of −8.2, −7.7, and −7.4 kcal/mol and entropy changes of −15.4, −19.1, and −20.9 cal/K mol were obtained for the association of NH3 onto Cl−, Br−, and I−, respectively. Comparison with the halide affinities of SO2 and H2O along with alkali affinities of NH3, SO2, and H2O suggests the importance of quadrupole moments and polarizabilities in the qualitative agreement of electrostatics with the ordering of association affinities. Electrostatic and ab initio calculations were made which suggest a variation of halide orientation with respect to the ammonia where I− is closest to alignment with the ammonia dipole and F− is farthest removed from the dipole axis. A value of 11 kcal/mol is estimated for association energy of NH3 with F− by comparison of extrapolated and calculated values along with similar chemical systems.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.452043
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