Multiple Choice
What molecule is removed from glucose molecules during the formation of maltose through glycosidic bond formation?
28. Carbohydrates
Monosaccharides - Cyclization
6:00 minutesProblem 59
Textbook Question
The aldaric acid of D-glucose forms two five-membered-ring lactones. Draw their structures.
Verified step by step guidance1
Understand the problem: Aldaric acids are dicarboxylic acids derived from aldoses by oxidizing both the aldehyde group and the terminal primary alcohol group to carboxylic acids. For D-glucose, this means both the C1 and C6 carbons are oxidized to carboxylic acids. Lactones are cyclic esters formed when a hydroxyl group reacts with a carboxylic acid group within the same molecule.
Identify the functional groups in D-glucose: D-glucose has hydroxyl (-OH) groups on carbons C2, C3, C4, and C5. After oxidation to aldaric acid, the molecule will have carboxylic acid groups at C1 and C6, and hydroxyl groups at the other carbons.
Determine the possible lactone formations: A five-membered ring lactone (γ-lactone) forms when the hydroxyl group on C4 or C5 reacts with the carboxylic acid group on C1. This creates two possible structures depending on which hydroxyl group participates in the reaction.
Draw the first lactone structure: For the first lactone, the hydroxyl group on C4 reacts with the carboxylic acid group on C1. This forms a five-membered ring with the following atoms: C1 (carboxylic acid carbon), O (from the hydroxyl group on C4), C4, C3, and C2. The remaining hydroxyl groups and the carboxylic acid group on C6 remain unchanged.
Draw the second lactone structure: For the second lactone, the hydroxyl group on C5 reacts with the carboxylic acid group on C1. This forms a five-membered ring with the following atoms: C1 (carboxylic acid carbon), O (from the hydroxyl group on C5), C5, C4, and C3. The remaining hydroxyl groups and the carboxylic acid group on C6 remain unchanged.
Verified video answer for a similar problem:This video solution was recommended by our tutors as helpful for the problem above
Video duration:
6mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Aldaric Acid
Aldaric acids are a type of dicarboxylic acid derived from aldoses, where both the aldehyde and the terminal alcohol group are oxidized to carboxylic acids. In the case of d-glucose, the aldaric acid formed is d-glucaric acid. Understanding the structure of aldaric acids is crucial for recognizing how they can undergo cyclization to form lactones.
Recommended video:
Guided course
03:10
Monosaccharides - Strong Oxidation (Aldaric Acid)
Lactone Formation
Lactones are cyclic esters formed when a hydroxyl group reacts with a carboxylic acid group within the same molecule, leading to the loss of water. In the case of d-glucose aldaric acid, two different five-membered lactones can be formed depending on which hydroxyl group participates in the reaction. This concept is essential for predicting the structures of the resulting lactones.
Recommended video:
Guided course
05:19Lactones and Lactams
Five-Membered Ring Structures
Five-membered ring structures, such as furanoses, are common in carbohydrate chemistry. They are formed when a sugar molecule cyclizes, creating a stable ring that can influence the molecule's reactivity and properties. Recognizing the formation of these rings from aldaric acids is key to drawing the correct structures of the lactones derived from d-glucose.
Recommended video:
Guided course
05:14Ring Expansion
12:58mWatch next
Master Monosaccharides - Cyclization with a bite sized video explanation from Johnny
Start learningRelated Videos
Related Practice