Hydrolysis of sucrose gives
(a) α-D-(-)-glucose and β-D-(-)-fructose
(b) α-D-(+)-glucose and β-D-(+)

Q: Why is sucrose considered a non-reducing sugar?

Sucrose is a non-reducing sugar because the glycosidic bond is formed between the anomeric carbon of glucose (C1) and the anomeric carbon of fructose (C2). Since both reducing groups are tied up in the bond, there is no free aldehyde or ketone group available to reduce reagents like Tollens' or Fehling's.

Q: What exactly does the 'D' stand for in D-glucose?

The 'D' refers to the stereochemical configuration of the highest-numbered chiral carbon (farthest from the carbonyl group). If the hydroxyl (-OH) group on this carbon points to the right in a Fischer projection, it is designated as 'D', matching the configuration of D-glyceraldehyde.

Q: How are the (+) and (-) signs different from D and L?

D and L refer to the structural geometry (relative configuration) of the molecule, while (+) and (-) refer to the experimental optical activity (direction in which the molecule rotates plane-polarized light). There is no direct correlation; a 'D' sugar can be either (+) or (-).

Q: What is an anomeric carbon?

The anomeric carbon is the carbon derived from the carbonyl carbon (the aldehyde or ketone group) of the open-chain form of the carbohydrate molecule. In the cyclic form, it is the carbon bonded to two oxygen atoms.

Q: Why is the product mixture called 'invert sugar'?

Before hydrolysis, sucrose has a positive specific rotation ($+66.5^\circ$). After hydrolysis, the mixture contains glucose ($+52.5^\circ$) and fructose ($-92.4^\circ$). Because the negative rotation of fructose is stronger, the net rotation of the mixture becomes negative. This 'inversion' of the optical sign gives it the name 'invert sugar'.

Question

Hydrolysis of sucrose gives

Options:

(A) $\alpha$-D-$(-)$-glucose and $\beta$-D-$(-)$-fructose

(B) $\alpha$-D-$(+)$-glucose and $\beta$-D-$(+)$-fructose

(C) $\alpha$-D-$(-)$-glucose and $\beta$-D-$(+)$-fructose

(D) $\alpha$-D-$(+)$-glucose and $\beta$-D-$(-)$-fructose

Sigma Percentile · Accepted Answer

### The Sweet Chemistry of Sucrose

Imagine stirring a spoonful of sugar into your morning tea. That common table sugar is scientifically known as **sucrose**, a fascinating disaccharide. But what happens when we break it down? The process of breaking down sucrose using water and an acid catalyst (or an enzyme like sucrase) is called **hydrolysis**.

When sucrose undergoes hydrolysis, it splits into its two fundamental building blocks—its constituent monosaccharides.

$$	ext{Sucrose} + H_2O \xrightarrow{H^+} 	ext{Glucose} + 	ext{Fructose}$$

### Decoding the Monosaccharides

To answer this question correctly, we need to know the exact stereochemical identity of these monosaccharides. Sucrose is formed by a glycosidic linkage between the anomeric carbon of glucose and the anomeric carbon of fructose.

Specifically, the glucose unit is in the **$\alpha$** form, and the fructose unit is in the **$\beta$** form. Furthermore, both of these naturally occurring sugars belong to the **D-series** of carbohydrates, meaning the hydroxyl group on their highest-numbered chiral center is on the right side in a Fischer projection.

### The Tale of Optical Rotation

Now, let's talk about how these molecules interact with light. When plane-polarized light passes through a solution of these sugars, they rotate the plane of the light.

Naturally occurring D-glucose rotates the light to the right (clockwise). We call this property **dextrorotatory**, and it is denoted by a **$(+)$** sign.

On the other hand, naturally occurring D-fructose rotates the light to the left (anticlockwise). This makes it **levorotatory**, which is denoted by a **$(-)$** sign.

### The Final Verdict

Combining all these intricate details, we can precisely name the products of sucrose hydrolysis:

1. **$\alpha$-D-$(+)$-glucose**
2. **$\beta$-D-$(-)$-fructose**

If we look at the given options, examiners often try to trick students by swapping the $(+)$ and $(-)$ signs or the $\alpha$ and $\beta$ designations. By staying sharp and remembering these facts, we can confidently conclude that **Option (d)** is the correct answer.

### Bonus Concept: Invert Sugar

Here is a beautiful piece of trivia: Pure sucrose is dextrorotatory (specific rotation of $+66.5^\circ$). However, after hydrolysis, the resulting mixture becomes levorotatory. Why? Because the levorotation of fructose ($-92.4^\circ$) overpowers the dextrorotation of glucose ($+52.5^\circ$).

Since the sign of rotation *inverts* from positive to negative during the reaction, the hydrolysis of sucrose is often called the **inversion of cane sugar**, and the resulting equimolar mixture of glucose and fructose is famously known as **invert sugar**.

Animated Solution for Chemistry - Biomolecules: Hydrolysis of sucrose gives

Select Answer:

Visualized Solution

\text{Hydrolysis of Sucrose}

\text{Products of Hydrolysis}

\text{Optical Rotation}

\text{Final Isomers}

\text{Correct Option}

\text{Invert Sugar}

The Sigma Insight: Carbohydrates

The Sweet Chemistry of Sucrose

Decoding the Monosaccharides

The Tale of Optical Rotation

The Final Verdict

Bonus Concept

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