Hydrogen bonding of hydroxy groups to carbanions in indenide and fluorenide derivatized alcohols directly observed by UV, IR, and NMR spectroscopy

Article abstract of DOI:10.1021/ja00063a019

For investigation of hydrogen bonding to carbanions a number of carbanions containing hydroxy groups have been designed and synthesized. The carbanions were of the type R′-CR₂-CHR-CR₂-OH, with R′ being an indenide or a fluorenide group and R a methyl group or a hydrogen, and were generated from the corresponding indenes and fluorenes. Intramolecular hydrogen bonding was observed by UV, IR, and NMR spectroscopy in both polar [dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF)] and apolar (benzene and toluene) non-hydrogen bond donor solvents with properly designed carbanions. In the latter solvents cryptand 211 was used for complexation of the counter Li⁺ cation. For some derivatives the presence of both intramolecular hydrogen bonding to the carbanion and intermolecular hydrogen bonding of the hydroxy group to the solvent was observed. The UV spectroscopy indicated the perturbation of the proton accepting carbanion and IR and NMR spectroscopy showed the effect of the hydrogen bonding on the proton donating OH group.