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Temperature and solvent effects on the experimental dipole moments of three crown ethers
Author(s) -
Caswell Lyman R.,
Savannunt Diana S.
Publication year - 1988
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570250111
Subject(s) - conformational isomerism , chemistry , cyclohexane , dipole , benzene , crown (dentistry) , solvent , polar , solvent effects , computational chemistry , crystallography , organic chemistry , molecule , materials science , physics , astronomy , composite material
Dipole moments of 12‐crown‐4, 15‐crown‐5 and 18‐crown‐6 have been measured for solutions in benzene and in cyclohexane at 15, 20 , 25, and 30°, using the Guggenheim‐Smith method. The dipole moments of the more common conformers of these crown ethers have also been calculated. The results indicate that these crown ethers exist in solution as mixtures of conformers. The conformational equilibria shift toward the more polar conformers as temperature increases. There is evidence that the more polar conformers of 12‐crown‐4 and 15‐crown‐5 are somewhat more favored in benzene solution than in cyclohexane, possibly as the result of a weak complexation with the former solvent.