18 Questions
What is the result of the reaction between the OH group on C5 and the aldehyde carbonyl during cyclization?
Formation of a six-membered ring
What is the difference between 𝛂-D-glucose and 𝛃-D-glucose?
Position of the OH group on the new chirality center
What happens during mutarotation in carbohydrates?
Conversion to an equilibrium mixture of two different carbohydrate forms
What is the product of a dehydration reaction between two monosaccharides?
Acetal and water
What is the role of a glycosidic bond in carbohydrates?
Joins carbohydrate molecules together by liberating water molecule
Which disaccharide is also known as malt sugar?
Maltose
In Fischer projections, how are the horizontal bonds represented?
As wedges
How is the configuration about the chiral center most distant from the carbonyl carbon used to differentiate D and L isomers?
By the stereochemistry of the hydroxyl group
How many chiral centers are present in glucose according to the text?
Four
Which statement is true regarding D and L isomers?
D and L isomers are enantiomers.
What defines D isomers in monosaccharides according to the text?
The stereochemistry at the most distant chiral center from the carbonyl carbon
What term describes sugars that differ only in the configuration around one carbon atom?
Epimers
When converting D-Glucose from Fischer projection to a cyclic monosaccharide, what is the first step?
Rotate the Fischer projection 90 degrees clockwise
In the Haworth projection of glucose, which OH group reacts with the aldehyde carbonyl to form a six-membered ring (pyranose)?
OH group on C5
What is the key difference between D-Glucose and L-Glucose in terms of chirality centers?
Their OH groups on the chirality center farthest from the carbonyl are different
Which statement best describes the chirality centers in a Fischer projection of a monosaccharide?
Chirality centers are represented by crosses
For a D monosaccharide, where is the OH group located in relation to the carbonyl group?
Farthest from the carbonyl on the right
Which type of sugars are glucose and other naturally occurring sugars?
D-sugars
Study Notes
Stereoisomers of Monosaccharides
- Glyceraldehyde has 2^1 = 2 stereoisomers
- Aldohexoses have 2^4 = 16 stereoisomers due to their four chiral centers
- Steroisomers of monosaccharides can be divided into two groups based on the configuration at the chiral center most distant from the carbonyl carbon
- D-isomers have the same configuration as D-glyceraldehyde, and L-isomers have the same configuration as L-glyceraldehyde
Fischer Projections
- Used to represent compounds with several chirality centers, such as aldohexoses
- The molecule is drawn with a vertical carbon skeleton, with the aldehyde at the top, and horizontal bonds are assumed to come forward (on wedges)
- The CH2OH group at the end of the chain ends up above the carbon skeleton
Cyclization and Anomers
- The OH group on C5 reacts with the aldehyde carbonyl to form a six-membered ring with a new chirality center
- Cyclization yields two isomers, α and β, depending on the location of the OH group on the new chirality center
- The α-isomer (α-D-glucose) has the OH group on the new chirality center drawn down
- The β-isomer (β-D-glucose) has the OH group on the new chirality center drawn up
Mutarotation
- The change in specific rotation that occurs when an α or β form of a carbohydrate is converted to an equilibrium mixture of the two
Disaccharides
- A disaccharide consists of two monosaccharides linked together by a glycosidic bond
- A glycosidic bond is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate, by liberating a water molecule
- Examples of disaccharides include maltose, composed of two D-glucose molecules
Monosaccharides
- Glucose and all other naturally occurring sugars are D-sugars
- L-Glucose, a compound that does not occur in nature, is the enantiomer of D-glucose
- L-Glucose has the opposite configuration at every chirality center
Haworth Structures
- A Haworth projection is a common way of writing a structural formula to represent the cyclic structure of monosaccharides
- The hydroxyl and carbonyl groups can react together to form a ring
- In glucose, the OH group on C5 reacts with the carbonyl carbon to form a six-membered ring (pyranoses)
Test your knowledge on Fischer projection and monosaccharide stereochemistry concepts. Learn the differences between D and L monosaccharides and how to determine their configurations. Explore the characteristics of D-sugars and the significance of L-glucose in stereochemistry.
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