Ionic hydrogen bond and ion solvation. 5. OH. O/sup -/ bonds. Gas-phase solvation and clustering of alkoxide and carboxylate anions

Journal Article · Wed Nov 26 04:00:00 EST 1986 · J. Am. Chem. Soc.; (United States)

OSTI ID:7203896

Mautner, M M.N.; Sieck, L W

Dissociation energies, ..delta..H/sup 0//sub D/, of RO/sup -/ x HOR, RCOO/sup -/ x HOR, and RCOO/sup -/ x HOOCR complexes range from 14 to 29 kcal/mol. Large values of ..delta..H/sup 0//sub D/ are observed for the symmetric dimers CH/sub 3/O/sup -/ x HOCH/sub 3/ (28.8 kcal/mol) and CH/sub 3/COO/sup -/ x HOOCCH/sub 3/ (29.3 kcal/mol). ..delta..H/sup 0//sub D/ decreases as the difference between the acidities of the components increase; e.g., for dimers with large ..delta delta..H/sup 0//sub acid/ such as CH/sub 3/COO/sup -/ x H/sub 2/O and HCOO/sup -/ x H/sub 2/O (..delta delta..H/sup 0//sub acid/ = 42.2 and 45.5 kcal/mol, respectively), ..delta..H/sup 0//sub D/ = 16.0 kcal/mol. For 13 dimers, a linear correlation of the form ..delta..H/sup 0//sub D/ = 28.4 - 0.29 ..delta delta..H/sup 0//sub acid/ is obtained. Some dimers deviate substantially from the correlation, suggesting special structural effects. For example, the large value of ..delta..H/sup 0//sub D/ = 36.8 kcal/mol for HCOO/sup -/ x HOOCH suggests double hydrogen bonding, involving a CH...O/sup -/ type bond. On the other hand, the data suggest that only one hydrogen bond is formed in RCOO/sup -/ x H/sub 2/O. Comparison between anionic and cationic hydrogen bonded systems shows that the bonding energies are similar for RO/sup -/ x B and ROH/sub 2//sup +/ x B complexes involving the same ligand B, suggesting primarily electrostatic interactions in both, while RCOO/sup -/ x B is weaker by 4-6 kcal/mol than RCOOH/sub 2//sup +/ x B, probably due to charge delocalization in RCOO/sup -/.

• Research Organization: National Bureau of Standards, Gaithersburg, MD
• OSTI ID: 7203896
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:24; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKOXIDES
ANIONS
BINDING ENERGY
CHARGED PARTICLES
CHEMICAL BONDS
DATA
DIMERS
DISSOCIATION ENERGY
ELECTRONIC STRUCTURE
ELEMENTS
ENERGY
EXPERIMENTAL DATA
FLUIDS
GASES
HYDROGEN
INFORMATION
IONS
LIGANDS
MOLECULAR STRUCTURE
NONMETALS
NUMERICAL DATA
PH VALUE
SOLVATION
THERMODYNAMICS