Identify the correct statements. Choose the correct answer from the options given below :
- A and B Only
- B and C Only
- A, B and D Only
- A, B and E Only
Answer
(4) A, B and E Only
Solution
A. Correct – glucose exists as α- and β-D-glucopyranose.
B. Correct – the two forms differ only in the configuration of the –OH at C–1 (anomeric carbon) of the cyclic hemiacetal.
C. Incorrect – as per NCERT, m.p. of α-form = 419 K and of β-form = 423 K, so the β-anomer melts higher.
D. Incorrect – the values are interchanged: α-D-glucose ≈ +112°, β-D-glucose ≈ +19°.
E. Correct – as per NCERT, the α-form is obtained by crystallisation from a concentrated solution at 303 K and the β-form from a hot saturated solution at 371 K.
∴ Correct statements: A, B and E
Answer: (4)