Question

Which of the following hexoses will form the same osazone when treated with excess phenyl-hydrazine?

• A. $D$-glucose, $D$-fructose and $D$-galactose
• B. $D$-glucose, $D$-fructose and $D$-mannose
• C. $D$-glucose, $D$-mannose and $D$-galactose
• D. $D$-fructose, $D$-mannose and $D$-galactose
• E. $D$-glucose, $D$-galactose and $D$-talose

Answer 1

Answer: (B)

D-glucose, D-fructose and D-mannose form the same osazone treated with excess phenyl hydrazine because they differ only 1st and 2nd carbon atoms which are transformed to the same form.
They form same osazone