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InterviewSolution
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Despite having an aldehyde group,Glucose does not give 2, 4-DNP test. What does this indicate? What is the significance of D and (+) here? |
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Answer» Glucose does not have open chain structure and hence it does not have a free –CHO group. Actually –CHO group combines with C5 –OH to form a hemiacetal. Glucose largely exists in the cyclic hemiacetal form along with a very small amount (0.5%) of the open chain form. Since the concentration of the open chain form is low and its reaction with 2, 4—DNP is reversible, therefore, formation of 2,4—DNP derivative cannot disturb the equilibrium to generate more of the open chain form from the cyclic hemiacetal form and hence it does not react with 2,4—DNP. The capital letter D in the name D-(+)-glucopyranose indicates that the C5—OH group is oriented towards right while the sign (+) indicates that glucopyranose is dextrorotatory. |
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