Xylitol
Xylitol is a chemical compound with the formula C5H12O5, or HO(CH2)(CHOH)3(CH2)OH; specifically, one particular stereoisomer with that structural formula. It is a colorless or white crystalline solid that is freely soluble in water. It can be classified as a polyalcohol and a sugar alcohol, specifically an alditol. The name derives from ξύλον, xyl[on] 'wood', with the suffix -itol used to denote sugar alcohols. Xylitol is used as a food additive and sugar substitute. Its European Union code number is E967. Replacing sugar with xylitol in food products may promote better dental health, but evidence is lacking on whether xylitol itself prevents dental cavities. Emil Fischer, a German chemistry professor, and his assistant Rudolf Stahel isolated a new compound from beech wood chips in September 1890 and named it Xylit, the German word for xylitol. The following year, the French chemist M.G. Bertrand isolated xylitol syrup by processing wheat and oat straw. Sugar rationing during World War II led to an interest in sugar substitutes. Interest in xylitol and other polyols became intense, leading to their characterization and manufacturing methods. Xylitol is one of three 5-carbon sugar alcohols. The others are arabitol and ribitol. These three compounds differ in the stereochemistry of the three secondary alcohol groups. Xylitol occurs naturally in small amounts in plums, strawberries, cauliflower, and pumpkin; humans and many other animals make trace amounts during metabolism of carbohydrates. Unlike most sugar alcohols, xylitol is achiral. Most other isomers of pentane-1,2,3,4,5-pentol are chiral, but xylitol has a plane of symmetry. Industrial production starts with lignocellulosic biomass from which xylan is extracted; raw biomass materials include hardwoods, softwoods, and agricultural waste from processing maize, wheat, or rice. The mixture is hydrolyzed with acid to give xylose. The xylose is purified by chromatography. Purified xylose is catalytically hydrogenated into xylitol using a Raney nickel catalyst.
