(i) The glucose pentaacetate does not react with hydroxylamine. This demonstrates that glucose does not include a free -CHO group.
(ii) Aldehydes produce hydrogen sulfite as a byproduct by giving 2,4 – DNP test, Schiff’s test, and reacting with NaHSO4. Glucose, on the other hand, does not go through these processes.
(iii) Glucose comes in two crystalline forms: alpha- and beta-glucose. The alpha–form (m.p. = 419 K) crystallizes from a concentrated glucose solution at 303 K, while the beta – form (m.p. = 423 K) crystallizes from a heated, saturated aqueous solution at 371 K. The open chain structure of glucose does not explain this behavior.