Write the reactions of D− glucose which can’t be explained by its open-chain structure. How can cyclic structure of glucose explain these reactions?

<p>This is a Long answer type Questions as classified in NCERT Exemplar</p><p><strong>Ans:&nbsp;</strong>The open chain structure of glucose explained the majority of its properties. However, it fails to explain the following facts:</p><p>I Although glucose has an aldehydic group, it does not undergo all aldehydic reactions.</p><p><strong> (a)</strong> Glucose does not react with ammonia, for example.</p><p><strong> (b)</strong> Glucose does not create an addition product when it combines with sodium bisulphite.</p><p><strong> (c) </strong>Glucose does not pass the Schiff's test or the 2, 4-DNP test, unlike other aldehydes.</p><p><strong> (ii) </strong>Glucose forms an oxime when it reacts with hydroxylamine, but glucose pentaacetate does not. This proves that glucose pentaacetate contains no aldehyde groups.</p><p><strong> (iii)</strong> There are two stereoisomeric forms of glucose: glucose and glucose. The melting temperatures and optical rotations of these two crystalline forms are different.</p><p><strong> (iv)</strong> Mutarotation occurs in an aqueous Ans of glucose, which means that its specific rotation decreases when compared to glucose and increases when compared to glucose.</p><p><strong> (v)</strong> Glucose produces isomeric methyl glucosides. Two isomeric monomethyl compounds are generated when glucose is burnt with methanol in the presence of dry hydrogen chloride gas.</p>

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