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The intermolecular hydrogen bondings of 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane(cryptand 22), 1,7-diaza-4,10,13-trioxacyclopentadecane(cryptand 21), 1,12,15-triaza-5,8-dioxa-3,4:9,10-dibenzocycloheptadecane (N3O2) and 1,12-diaza-5,8-dioxa-3,4:9,10-dibenzocyclotetradecane (N2O2) have been studied in chloroform solutions by 1H-nmr spectrometry at various temperatures. The molecules dimerize each other with the hydrogen bonds through N-H groups in the dilute solutions. The formation constants of the hydrogen bonds are in the order of cryptand 22 > cryptand 21 > N3O2 > N2O2. It appears that the constants depend on the molecular symmetry, the number of N-H group, and the localization of N-H groups in the molecule.
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