More than a million tons of sorbitol are produced in this way every year. HOCH 2CH(OH)CH(OH)CH(OH)CH(OH)CHO + H 2 → HOCH 2CH(OH)CH(OH)CH(OH)CH(OH)CH HO H The conversion of glucose and mannose to sorbitol and mannitol is given as: Mannitol is no longer obtained from natural sources currently, sorbitol and mannitol are obtained by hydrogenation of sugars, using Raney nickel catalysts. sorbitol can be dehydrated to isosorbide.
They can, however, be dehydrated to give cyclic ethers, e.g.
Unlike sugars, which tend to exist as rings, sugar alcohols do not. They are further differentiated by the relative orientation ( stereochemistry) of these –OH groups. They have one –OH group attached to each carbon. Most have five- or six-carbon chains, because they are derived from pentoses (five-carbon sugars) and hexoses (six-carbon sugars), respectively. The sugar alcohols differ in chain length. In contrast, sugars have two fewer hydrogen atoms, for example HOCH 2(CHOH) nCHO or HOCH 2(CHOH) n−1C(O)CH 2OH. Sugar alcohols have the general formula HOCH 2(CHOH) nCH 2OH.
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