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|Section2= |Section3= }} Isosaccharinic acid (ISA) is a six-carbon sugar acid which is formed by the action of calcium hydroxide on lactose and other carbohydrates. It is of interest because it may form in intermediate-level nuclear waste stores when cellulose is degraded by the calcium hydroxide in cements such as Portland cement. The calcium salt of the alpha form of ISA is very crystalline and quite insoluble in cold water, but in hot water it is soluble. ISA is thought to form by means of a series of reactions in which calcium ions acting as lewis acids catalyze two of the three steps. The first step is likely to be a rearrangement of the reducing sugar end of the cellulose (or lactose) into a keto sugar, the second step is likely to be a reaction similar to the base catylised dehydration which oftein occurs after an aldol reaction. In this second step an alkoxide (derived from a sugar) takes the role of the hydroxide leaving group, this second step is not likely to require the lewis acidity of the calcium. The final step is a benzilic acid rearrangement from a 1,2-diketone (1,5,6-trihydroxyhexane-2,3-dione) which is formed from the carbohydrate.4 Under acidic conditions sugars tend to form furans such as furfural and 5-hydroxymethylfurfural by a series of dehydrations of the carbohydrate. In acidic solutions the acid tends to form a 5-membered ring (lactone) by forming an ester between the carboxylic acid group and one of the alcohols. When treated with under anhydrous conditions with acetone, an acid and a dehydration agent two of the alcohol groups can be protected as a cyclic acetone acetal thus leaving behind only one alcohol,2 prolonged treatment with 2,2-dimethoxypropane forms a protected form of ISA where all four of the alcohol groups are protected as acetone acetals and the carboxylic acid is in the form of the methyl ester.3 These protected forms of ISA have been used as a starting material for chiral organic compounds anthracyclines.2 ==References== 2. Florent, J. C.; Ughetto-Monfrin, J.; Monneret, C., Journal of Organic Chemistry, 1987, volume 52, issue 6, pages 1051-1056. 3. Florent, Jean-Claude; Genot, Agnes; Monneret, Claude, Tetrahedron letters, 1985, vol 26, issue 43, pages 5295 - 5298. 4. Whistler; Be Miller, Journal of the American Chemical Society, 1960, volume 82, page 3705. 5. P N Humphreys, A Laws, J Dawson (2010) A Review of Cellulose Degradation and the Fate of Degradation Products Under Repository Conditions. SERCO / TAS / 002274 / 001. Serco Contractors Report for the Nuclear Decommissioning authority, UK. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Isosaccharinic acid」の詳細全文を読む スポンサード リンク
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