Specific rotations of freshly prepared aqueous solutions of I and II are +112 and +18.7, respectively. On… · ABC26OR0813
Subject: Organic Chemistry · Chapter: Natural Products · Topic: Natural Products & – General · Exam: JAM 2005-2022 · Marks: 2 · Difficulty: Medium
Specific rotations of freshly prepared aqueous solutions of I and II are +112 and +18.7, respectively. On standing the optical rotation of aqueous solution of I slowly decreases to give a final value of +52.7 due to equilibrium with II. Under this state of equilibrium, what is the ratio II : I? 
I 
II $[\alpha]_{\mathrm{D}}^{25}=+112$ $[\alpha]_{\mathrm{D}}^{25}=+18.7$
I II $[\alpha]_{\mathrm{D}}^{25}=+112$ $[\alpha]_{\mathrm{D}}^{25}=+18.7$(a)0.57
(b)1.00
(c)1.75
(d)5.9
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
Let x be the fraction of α-anomer (I): 112x + 18.7(1 − x) = 52.7 ⇒ x = 0.364. II : I = 0.636/0.364 = 1.75.
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