Question

Identify the sugar containing $\alpha, \beta$-1,2-glycosidic linkage.

• A. Sucrose
• B. Maltose
• C. Lactose
• D. Raffinose

Hint:

Sucrose is uniquely formed by locking the two reducing/anomeric carbons of its component monomers together (C1 of glucose and C2 of fructose). This head-to-head structural arrangement is why it is the only common non-reducing disaccharide and the only one with a 1,2-linkage.

Answer 1

The Correct Option is A

Step 1: Understand the clue.
We need the sugar whose two units are joined through an $\alpha,\beta$-1,2-glycosidic linkage, meaning both anomeric carbons (C1 of one, C2 of the other) are tied up in the bond.
Step 2: Test sucrose.
Sucrose joins $\alpha$-D-glucose (through its C1) to $\beta$-D-fructose (through its C2). That is exactly an $\alpha,\beta$-1,2 link.
Step 3: Test maltose.
Maltose links two glucose units by an $\alpha$-1,4 bond, not 1,2.
Step 4: Test lactose.
Lactose links galactose and glucose by a $\beta$-1,4 bond, not 1,2.
Step 5: Test raffinose.
Raffinose is a trisaccharide; its galactose is attached $\alpha$-1,6, so it does not fit the simple 1,2 description either.
Step 6: A confirming feature.
Because both anomeric carbons of sucrose are locked in the bond, sucrose is a non-reducing sugar - a hallmark of the 1,2 linkage. The answer is option (1).
\[ \boxed{\text{Sucrose has the } \alpha,\beta\text{-1,2 linkage}} \]