105399-89-1Relevant articles and documents
Conformational Studies on Model Compounds of Polyamides with Ether Groups in Their Structure
Abajo, J. de,Campa, J. G. de la,Riande, E.,Garcia, J. M.,Jimeno, M. L.
, p. 8669 - 8674 (1993)
The synthesis of 1,5-dibenzamido-3-oxapentane (DEBA) and 1,8-dibenzamido-3,6-dioxaoctane (TEBA), model compounds of polyamides with repeating units and , respectively, is reported.The mean-square dipole moment, 2>, of both compounds was measured in dioxane solutions in the interval of temperatures 30-60 deg C.The values of this quantity lie in the ranges 24.6-24.5 D2 and 25.4-26.0 D2, for DEBA and TEBA, respectively.The analysis of the spectral patterns of the model compounds indicates that the energy E?' of gauche states about the CH2-CH2 bonds adjacent to the amide groups is 0.44+/-0.08 kcal mol-1 below that of the alternative trans states.Moreover, semiempirical calculations show that gauche states about NH-CH2 bonds are also preferred over the alternative trans, in contrast with CH2-O bonds in polyesters, where the opposite occurs.The critical interpretation of the dipole moments of both DEBA and TEBA by the rotational isomeric state (RIS) model suggests that their polarities are very sensitive to the modulus of the dipole moments associated with the amide groups, but they are nearly insensitive to their orientation.Calculations of the dipolar distribution and the corresponding average energies carried out for DEBA and TEBA suggest that the conformers of higher polarity also have the highest energy.
