DETERMINATION OF EMPIRICAL POLARITY PARAMETERS OF THE CELLULOSE SOLVENT N,N-DIMETHYLACETAMIDE LICL BY MEANS OF THE SOLVATOCHROMIC TECHNIQUE/

Empirical solvatochromic polarity parameters (alpha-, beta-, and pi, AN and DN, as well as E-T(30)-values) for cellulose, N,N-dimethylaceta mide (DMA)/LiCl and cellulose dissolved in DMA/LiCl are presented. The following solvent polarity indicators were applied: phenyI-4-(2,4,6-t riphenyl-1-pyridinio)-1-phenolate (1),bis(4-N,N-dimethylamino)-benzoph enone (MK, 2), iron(II)-di-cyano-bis(1,10)-phenanthroline, Fe(phen)(2) (CN)(2), (3), and r(II)-N,N,N',N'-tetramethyl-ethylendiamine-acetyl- a cetonate tetraphenylborate/chloride/bromide (Cu(tmen)(acac)(+) X- (4). The solvatochromic shifts (nu(max)) of the indicators 1, 2, 3, and 4 adsorbed to cellulose or dissolved in DMA/LiCl reflect the correspondi ng properties of the surrounding, the dipolarity/polarizability (pi), the hydrogen bond donating ability or Lewis acidity (alpha), and the hydrogen bond accepting ability or Lewis basicity (beta), respectively . Any indicator employed is well characterized (r > 0.97) by a linear solvation energy relationship (LSER) taking the Kamlet and Taft parame ter into account: nu(max)(indicator)= nu(max,0) + s pi + alpha alpha + b beta. Cellulose, DMA/LiCl, and the cellulose/DMA/LiC1 solution app roach a similar polarity with an ET(30) parameter about 52 to 53 kcal mol(-1). The hypothetical interaction strength parameter (acid-base in teractions, dipolar-dipolar interactions) between cellulose and DMA/Li Cl are calculated by means of the individual Kamlet-Taft parameters al pha, beta, and pi of cellulose and DMA/LiCI via a multiparameter equa tion. The specific chloride/cellulose interaction plays a dominant rol e in the cellulose solvent DMA/LiCl. Comparison of the polarity parame ters of DMA/LiCl with the polarity parameters of other mixtures-such a s N,N-dimethyl-formamide/LiCl, DMA/NaCl, or DMA/LiBr-are presented as well. (C) 1998 John Wiley & Sons, Inc.