Question

Give chemical reactions to show the presence of an aldehyde group and straight chain in glucose.

Answer 1

Glucose, a monosaccharide, contains an aldehyde group and a straight chain. One of the reactions to show the aldehyde group is the reaction with Tollen’s reagent, which forms a silver mirror. The reaction is: \[ \text{C}_6\text{H}_{12}\text{O}_6 + 2[Ag(NH_3)_2]^+ \rightarrow \text{C}_6\text{H}_{12}\text{O}_6^{\text{(oxidized)}} + 2Ag \] To show the straight chain structure, glucose undergoes oxidation and reduction, demonstrating the open-chain form.

Answer 2

Anomers are a type of stereoisomer found in cyclic carbohydrates. They differ in the configuration around the anomeric carbon, which is the carbonyl carbon of the open-chain form that becomes chiral after cyclization. The two anomers are typically referred to as $\alpha$-anomer and $\beta$-anomer, depending on the orientation of the hydroxyl group attached to the anomeric carbon.

Answer 3

The structure of $\beta$-D-Glucopyranose is as follows: \[ \chemfig{*5([O]C1-OC(CO)C(O)-C(O)-C(O)-C1O)} \] This structure represents the $\beta$-anomer of D-glucopyranose, where the hydroxyl group at the anomeric carbon (carbon 1) is on the opposite side of the ring relative to the CH2OH group.

Answer 4

Sucrose is a disaccharide composed of glucose and fructose. When sucrose undergoes hydrolysis in the presence of an acid or enzyme, it breaks into glucose and fructose. This reaction inverts the optical rotation, as sucrose is dextrorotatory and the resulting mixture of glucose and fructose is levorotatory. This phenomenon is why sucrose is called "invert sugar."