New lubricants from vegetable oil: cyclic acetals of methyl 9,10-dihydroxystearate

Potential new lubricants and fuel lubricity enhancers have been prepared from methyl 9,10-dihydroxystearate and long chain aldehydes to form the corresponding cyclic acetals. These materials are oils down to low temperatures, as compared to symmetric ketals derived from the same diol, which are waxes at room temperature. The acetals form in an equilibrium reaction (Keq ≈ 60) which suggests they will be stable as fuel additives. The viscosities of the new oils are close to those predicted for normal paraffins with the same number of non-hydrogen atoms, but the acetal structure has subtle effects on viscosity as compared to branched alkanes. Acetals with long alkyl branches maintain higher viscosity on a molecular weight basis compared to branched alkanes. The qualitative relationship between branch length and viscosity is discussed. These acetals are potential candidates for novel biobased lubricants.