Conformations of sym-(R)(OR')dibenzo-16-crown-5 compounds with R = decyl and R' = H, CH 3, CH 2CO 2H, and CH 2CO 2CH 3, as well as R = alkyl, fluoroalkyl, alkenyl, and alkynyl and R' = CH 2CO 2H, in solution have been probed by NMR spectroscopy. The difference in chemical shifts of the diastereotopic hydrogens for the methylene groups adjacent to the geminally substituted ring carbon is utilized to assess the ease of inversion of the three-carbon bridges. For lariat ethers with R = C 10H 21, the chemical shift difference is much larger when R' = CH 2CO 2H and CH 2CO 2CH 3 than H and CH 3. In non-hydrogen bonding solvents, the chemical shift difference for lariat ethers with R = C 10H 21 is much larger when R' = CH 2CO 2H than CH 2CO 2CH 3 which demonstrates intramolecular hydrogen bonding of the carboxylic acid-containing side arm with a crown ether oxygen.
|Number of pages||5|
|Publication status||Published - 1996 Dec 1|
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