Question

Which one of the following is called 'invert sugar'?

• A. Maltose
• B. Sucrose
• C. Glucose
• D. Fructose

Hint:

Carbohydrate Facts:
Invert Sugar = Hydrolyzed SUCROSE (Equimolar Glucose + Fructose, net Levorotatory).
Milk Sugar = Lactose.
Malt Sugar = Maltose.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Carbohydrate optical rotation inversion: equimolar enzymatic or acid hydrolysis of dextrorotatory sucrose yields a levorotatory equimolar mixture of D-glucose and D-fructose called invert sugar.
Key Formula or Approach:
\[ \text{Sucrose } ([lpha]_D = +66.5^\circ) \xrightarrow{\text{Invertase / Acid}} \underbrace{\text{D-Glucose } (+52.5^\circ) + \text{D-Fructose } (-92.4^\circ)}_{\text{Invert Sugar Mixture } ([lpha]_D = -19.9^\circ)} \]

Step 2: Detailed Explanation:
In carbohydrate chemistry:
- Sucrose is a non-reducing disaccharide ($lpha$-D-glucopyranosyl-(1$ ightarrow$2)-$eta$-D-fructofuranoside) that is dextrorotatory ($[lpha]_D = +66.5^\circ$).
- Upon acid or enzymatic (invertase) hydrolysis, it splits into equimolar amounts of D-glucose and D-fructose.
- Because the strong levorotatory power of D-fructose ($-92.4^\circ$) exceeds the dextrorotatory power of D-glucose ($+52.5^\circ$), the optical rotation 'inverts' from positive ($+66.5^\circ$) to negative ($-19.9^\circ$).
- Hence, hydrolyzed sucrose (and sucrose as its parent source) is called Invert Sugar.

Step 3: Final Answer:
Hence, Sucrose is related to called invert sugar, corresponding to option (B).