| Assertion : The specific rotation of a freshly prepared solution of a-glucose decreases from \[+112{}^\circ \] to \[52.7{}^\circ \] while that of (\[\beta \]-glucose increases from \[+\text{ }19{}^\circ \] to \[52.7{}^\circ \]. |
| Reason : The change in specific rotation of an optically active compound with time to an equilibrium value is called mutarotation. |
A) Assertion and reason both are correct statements and reason is correct explanation for assertion.
B) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C) Assertion is correct statement but reason is wrong statement.
D) Assertion is wrong statement but reason is correct statement.
Correct Answer: B
Solution :
Glucose exists in two forms, i.e. \[\alpha \]-D-glucose with a specific rotation of \[+112{}^\circ \] and \[\beta \]-D-glucose with a specific rotation of \[+19{}^\circ \]. However, when either of these two forms is dissolved in water and allowed to stand, it gets converted into the same equilibrium mixture of both the \[\alpha \]- and \[\beta \]-forms with a small amount of open chain form. As a result of this equilibrium, the specific rotation of a freshly prepared solution of \[\alpha \]-glucose decreases from \[+112{}^\circ \] to \[52.7{}^\circ \] while that of \[\beta \]-glucose increases from \[+19{}^\circ \] to \[52.7{}^\circ \].
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