(g)Aldonic acids tend to exist as lactones. A-lactone has a six-membered ring.(h)A-lactone has a five-membered ring.(i)Aldaric acids have carboxylic acid groups at both ends of the chain.25.19(a)Reduction of aldoses with sodium borohydride yields polyhydroxylic alcohols calledalditols.Optically inactive alditols are those that have a plane of symmetry, that is, those thatare meso forms. TheD-aldohexoses that yield optically inactive alditols areD-allose andD-galactose.HHHOHOHCHOHOHOHCH2OHCHOHHOHOHHOHHOHCH2OHCH2OHCH2OHHHOHOHHOHHOHNaBH4NaBH4d-AlloseAllitol(meso compound)Galactitol
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