PARTITION-COEFFICIENTS OF FUEL SYSTEM ICING INHIBITORS - SEMIEMPIRICAL MOLECULAR-ORBITAL CALCULATIONS

In our continuing efforts to design nontoxic and biodegradable fuel sy stem icing inhibitor (FSII) compounds with improved fuel solubility an d antiicing ability, and nontoxic deicers for aircraft and runways, we report semiempirical molecular orbital calculations of hexadecane-wal ker partition coefficients (log Ph-w). The evaluation of hexadecane-wa ter partition coefficients for;a series of isomers by an empirical met hod yields only a single number, whereas our application of solvent mo dels within a molecular orbital approach to methyl- and acetyl-substit uted D-glucopyranose results in a range of log Ph-w values. Furthermor e, these values are lowered when the conformational response of the FS II to the solvent is included. The extent of this effect depends on th e solvation model used and is more pronounced for acetyl-substituted g lucopyranoses than for methyl-substituted derivatives. Four methyl sub stituents in any substitution pattern are required for preferential pa rtitioning into fuel whereas only specific tetraacetylglucopyranose is omers-1,2,3,4-alpha-D-tetraacetylglucopyranose, 1,2,3,6-alpha-D-tetraa cetylglucopyranose, 1,2,4,6-alpha-D-tetraacetylglucopyranose, 1,2,4,6- beta-D-tetraacetylglucopyranose, 1,3,4,6-alpha-D-tetraacetylglucopyran ose, and 1,3,4,6-beta-D-tetraacetylglucopyranose-will do so.