Glossary

25.4 Configurations of the Aldoses

2 min read•may 7, 2024

are sugar molecules with an aldehyde group. They come in different sizes and shapes, creating a variety of . Understanding their configurations is key to grasping how these important biological molecules function.

help visualize aldose structures in 2D. D and L configurations, along with mnemonics for remembering specific aldoses, make it easier to navigate the complex world of sugar .

Configurations of Aldoses

Stereoisomers of aldoses

Top images from around the web for Stereoisomers of aldoses

  • Organic chemistry 10: Stereochemistry - chirality, enantiomers and diastereomers View original

    Is this image relevant?

  • Stereoisomerism - Wikipedia View original

    Is this image relevant?

  • Organic chemistry 10: Stereochemistry - chirality, enantiomers and diastereomers View original

    Is this image relevant?

1 of 3

Top images from around the web for Stereoisomers of aldoses

  • Organic chemistry 10: Stereochemistry - chirality, enantiomers and diastereomers View original

    Is this image relevant?

  • Stereoisomerism - Wikipedia View original

    Is this image relevant?

  • Organic chemistry 10: Stereochemistry - chirality, enantiomers and diastereomers View original

    Is this image relevant?

1 of 3
  • Aldoses are monosaccharides contain an aldehyde functional group and are classified by the number of carbon atoms
    • has 3 carbons (), has 4 carbons (), has 5 carbons (, ), and has 6 carbons (, )
  • Stereoisomers have the same molecular formula but different spatial arrangements of atoms
    • Aldoses contain allowing for the existence of stereoisomers
      • Number of stereoisomers increases with the number of chiral centers
        • 2n2^n possible stereoisomers for n chiral centers
    • are non-superimposable mirror images of each other
      • D and L notation distinguishes between enantiomers
    • are stereoisomers that are not mirror images of each other
      • are diastereomers that differ at only one chiral center

Fischer projections of monosaccharides

  • represent the three-dimensional structure of a molecule in a two-dimensional drawing
    • Horizontal lines represent bonds coming out of the plane towards the viewer
    • Vertical lines represent bonds going behind the plane away from the viewer
  • D and L configurations determined by the orientation of the hydroxyl group on the chiral center farthest from the aldehyde group
    • has the hydroxyl group on the right side
    • has the hydroxyl group on the left side
  • Common monosaccharides in D and L configurations:
    • and (trioses)
    • and (tetroses)
    • , , , and (pentoses)
    • , , , and (hexoses)

Mnemonics for aldose structures

  • Mnemonics help remember the names and configurations of and
    • "All Altruists Gladly Make Gum in Gallon Tanks" for aldohexoses:
      1. (all R)
      2. (RLRR)
      3. Glucose (RLRS)
      4. (RLSR)
      5. (RSRR)
      6. (RSSR)
      7. Galactose (RSRS)
      8. (RSSR)
    • "Rarely Let Very Xylophones Ruin" for aldopentoses:
      1. Ribose (all R)
      2. (RLRR)
      3. Xylose (RLRS)
      4. (RLSR)

Stereochemistry and Optical Activity

  • Stereochemistry studies the three-dimensional arrangement of atoms in molecules
  • refers to molecules that are non-superimposable on their mirror images
    • Chiral molecules contain at least one (a carbon bonded to four different groups)
  • is the ability of chiral compounds to rotate plane-polarized light
  • are used to assign R or S configuration to chiral centers

Key Terms to Review (51)

Aldohexoses: Aldohexoses are a class of monosaccharides, the simplest form of carbohydrates, that contain six carbon atoms and have an aldehyde group at one end. They are the most common and biologically important group of hexoses, which are essential for various metabolic processes in living organisms.
Aldopentoses: Aldopentoses are a class of monosaccharides that contain five carbon atoms and have an aldehyde group at one end. They are important in the context of understanding the configurations of aldoses, which are a type of monosaccharide.
Aldoses: Aldoses are a class of monosaccharides, the simplest form of carbohydrates, that have an aldehyde group (CHO) at the first carbon atom. They are one of the two main types of monosaccharides, the other being ketoses, which have a ketone group (C=O) at the second carbon atom.
Allose: Allose is a rare aldose sugar that is one of the eight common stereoisomeric forms of the monosaccharide glucose. It is characterized by its unique configuration and properties within the context of the configurations of aldoses.
Altrose: Altrose is a rare aldose sugar that is one of the 16 possible stereoisomers of the hexose monosaccharide. It is closely related to other aldose sugars and plays a role in the configurations of these molecules, particularly in the context of 25.4 Configurations of the Aldoses.
Anti stereochemistry: Anti stereochemistry describes the spatial arrangement in a chemical reaction where two substituents are positioned on opposite sides of a double bond or ring structure after the reaction. It is particularly relevant in the halogenation of alkenes, resulting in products where the added atoms are located across from each other.
Asymmetric Carbon: An asymmetric carbon, also known as a chiral carbon, is a carbon atom that is bonded to four different substituents. This unique arrangement gives the molecule the ability to exist in two non-superimposable mirror-image forms, known as enantiomers, which have important implications in organic chemistry and biochemistry.
Cahn-Ingold-Prelog Priority Rules: The Cahn-Ingold-Prelog priority rules are a set of guidelines used to assign a priority order to the substituents attached to a chiral carbon atom. This allows for the unambiguous determination of the stereochemistry of a molecule, which is crucial in the field of organic chemistry.
Chiral Centers: Chiral centers are atoms within a molecule that have four different substituents attached, resulting in a non-superimposable mirror image. This asymmetry gives rise to the concept of chirality, which is essential in understanding optical activity, meso compounds, and the stereochemistry of various organic reactions and biomolecules.
Chirality: Chirality is a fundamental concept in organic chemistry that describes the three-dimensional arrangement of atoms in a molecule. It refers to the property of a molecule that is non-superimposable on its mirror image, resulting in the existence of two distinct forms known as enantiomers. Chirality is a crucial factor in understanding the behavior and properties of various organic compounds, including their interactions with living systems.
Chirality centers: A chirality center in organic chemistry is an atom, typically carbon, that has four different groups attached to it, leading to non-superimposable mirror image forms of the molecule. These centers are crucial for determining the 3D spatial orientation of molecules, affecting their chemical behavior and interactions.
D Configuration: D configuration is a system used to assign the absolute stereochemistry of chiral carbon centers in organic molecules. It is based on the Cahn-Ingold-Prelog (CIP) priority rules, which determine the priority of substituents attached to the chiral center.
D-erythrose: D-erythrose is an aldose, a monosaccharide with an aldehyde group at the end of the carbon chain. It is one of the four stereoisomers of the simple sugar erythrulose, and is classified as a D-sugar based on the configuration of the chiral carbon atoms.
D-galactose: D-galactose is a monosaccharide, or simple sugar, that is an important component of many complex carbohydrates. It is a C-4 epimer of D-glucose, meaning it differs in the configuration of the hydroxyl group at the fourth carbon. D-galactose is a key term in understanding the topics of D,L Sugars and the Configurations of Aldoses.
D-glucose: D-glucose is a monosaccharide, the most abundant sugar found in nature. It is an aldose, meaning it has an aldehyde group at one end, and is the stereoisomer with the D-configuration, indicating the position of the hydroxyl group on the chiral carbon farthest from the aldehyde group.
D-glyceraldehyde: D-glyceraldehyde is a simple monosaccharide, specifically an aldose, that serves as an important model compound for understanding the configurations of sugars. It is the simplest possible aldose, containing three carbon atoms and a single aldehyde group.
D-ribose: D-ribose is a monosaccharide, a type of simple sugar, that is an essential component of ribonucleic acid (RNA). It is a key player in the topics of enantiomers, D-L sugars, and the configurations of aldoses.
D-sugar: D-sugar, also known as dextrose, is a type of monosaccharide that is the primary form of glucose found in the human body. It is an aldose, meaning it has an aldehyde group at the end of the carbon chain, and it has a specific stereochemical configuration around the chiral carbon atoms.
D-Xylose: D-Xylose is a monosaccharide, specifically an aldose, that is a common constituent of hemicellulose in plant cell walls. It is a naturally occurring sugar that is important in the context of understanding the configurations of aldoses, a key topic in organic chemistry.
Diastereomers: Diastereomers are a type of stereoisomer that have the same molecular formula and connectivity, but differ in their three-dimensional arrangement of atoms in space. They are not mirror images of each other and do not exhibit the property of chirality.
Enantiomers: Enantiomers are a pair of stereoisomers that are non-superimposable mirror images of each other. They have the same molecular formula and connectivity, but differ in the spatial arrangement of their atoms, resulting in a unique handedness or chirality.
Epimers: Epimers are a type of stereoisomers that differ in the configuration of only one stereocenter, or chiral carbon, within a molecule. This subtle difference in the spatial arrangement of atoms can have significant implications in the context of carbohydrate chemistry and stereochemistry.
Erythrose: Erythrose is a monosaccharide, specifically an aldose, that contains four carbon atoms. It is a member of the erythrulose family and is an important intermediate in various metabolic pathways, particularly those related to the configurations of aldoses.
Fischer projections: Fischer projections are a two-dimensional drawing method used in organic chemistry to represent the three-dimensional spatial arrangement of atoms around chiral centers, primarily in carbohydrates. This method uses horizontal lines to represent bonds projecting forward (out of the plane) and vertical lines for bonds projecting backward (into the plane).
Fischer Projections: Fischer projections are a way of representing the three-dimensional stereochemistry of organic molecules, particularly carbohydrates, on a two-dimensional plane. They are named after the German chemist Emil Fischer, who developed this method of depicting the spatial arrangement of atoms in a molecule.
Galactose: Galactose is a monosaccharide, or simple sugar, that is a C-4 epimer of glucose. It is an important component of lactose, the primary sugar found in mammalian milk, and is also produced in the body during the metabolism of lactose.
Glucose: Glucose is a simple sugar, or monosaccharide, that serves as the primary source of energy for the body's cells. It is a key component in various metabolic processes and plays a central role in carbohydrate chemistry and biochemistry.
Glyceraldehyde: Glyceraldehyde is a simple sugar (monosaccharide) that is an important intermediate in various metabolic pathways, particularly in the process of glycolysis. It is the simplest aldose, containing a single aldehyde group and three carbon atoms.
Gulose: Gulose is one of the eight aldose monosaccharides, which are the simplest carbohydrates that contain an aldehyde group. It is a C-3 epimer of glucose, meaning it has the same molecular formula but a different spatial arrangement of the hydroxyl groups around the third carbon atom.
Hexose: A hexose is a monosaccharide, or the simplest form of carbohydrate, containing six carbon atoms. Hexoses are the most common and biologically important class of carbohydrates, playing crucial roles in energy production, structural support, and signaling within living organisms.
Idose: Idose is a monosaccharide, a type of simple sugar, that is a C-3 epimer of glucose. It is a member of the aldose family, which are monosaccharides containing an aldehyde group at the terminal carbon. Idose is particularly relevant in the context of understanding the configurations of aldoses, as discussed in section 25.4 of the curriculum.
L Configuration: L configuration refers to the spatial arrangement of atoms or functional groups around a chiral carbon center, where the priority of the substituents is such that the lowest priority group is positioned on the left side when the molecule is viewed with the highest priority group facing the observer. This configuration is an important concept in the context of understanding the configurations of aldoses.
L-Erythrose: L-Erythrose is an aldose, a monosaccharide with an aldehyde group at one end. It is one of the four stereoisomers of the tetrose sugar erythrulose, and specifically refers to the L-configuration of the molecule.
L-Galactose: L-Galactose is an aldose, a monosaccharide with an aldehyde group at one end. It is the C-4 epimer of D-glucose, meaning it has the same chemical formula but the hydroxyl group on the fourth carbon is in the opposite orientation.
L-glucose: L-glucose is the enantiomer of the more common D-glucose, with the hydroxyl groups arranged in the opposite configuration around the chiral carbon atoms. As a result, L-glucose exhibits the opposite optical activity compared to D-glucose, making it an important concept in the study of optical activity, the classification of sugars, and the configurations of aldoses.
L-glyceraldehyde: L-glyceraldehyde is a simple monosaccharide, or sugar, that serves as an important intermediate in various metabolic pathways. It is the aldose form of glycerol, with a single aldehyde group and three carbon atoms. L-glyceraldehyde is a key component in understanding the concepts of D,L sugars and the configurations of aldoses.
L-Ribose: L-Ribose is a monosaccharide, a type of aldose, that is the structural component of ribonucleic acid (RNA). It is an important sugar in the context of the configurations of aldoses, as it represents one of the stereoisomeric forms that aldoses can adopt.
L-sugar: L-sugar, also known as left-handed sugar, is a type of monosaccharide that is the mirror image of the more common D-sugar. L-sugars have the opposite configuration of their carbon atoms compared to the D-sugars, which are the predominant form found in nature and in living organisms.
L-Xylose: L-Xylose is a naturally occurring aldose sugar with the molecular formula C₅H₁₀O₅. It is the enantiomer of the more common D-xylose, and is found in various plant materials, including wood, straw, and corn cobs. L-Xylose is an important monosaccharide in the context of understanding the configurations of aldoses.
Lyxose: Lyxose is a monosaccharide, specifically an aldose, that is one of the less common naturally occurring sugars. It is a C-3 epimer of ribose, meaning it has the same molecular formula but a different spatial arrangement of the hydroxyl groups around the third carbon atom.
Mannose: Mannose is a monosaccharide, a type of simple sugar, that is an aldose with the chemical formula C₆H₁₂O₆. It is an important carbohydrate found in various organisms and plays crucial roles in the context of the topics 25.4 Configurations of the Aldoses, 25.5 Cyclic Structures of Monosaccharides: Anomers, and 25.7 The Eight Essential Monosaccharides.
Optical Activity: Optical activity is the ability of certain molecules to rotate the plane of polarized light as it passes through a solution containing those molecules. This phenomenon is directly related to the concept of chirality, where molecules can exist in two non-superimposable mirror-image forms, known as enantiomers.
Pentose: A pentose is a monosaccharide, or simple sugar, that contains five carbon atoms. Pentoses are an important class of carbohydrates that play a crucial role in the configurations of aldoses and the classification of carbohydrates.
Ribose: Ribose is a monosaccharide, a type of simple sugar, that is an essential component of ribonucleic acid (RNA). It is a pentose sugar, meaning it has five carbon atoms, and is the backbone of the RNA molecule, playing a crucial role in various biological processes.
Ribulose: Ribulose is a five-carbon sugar that is an important intermediate in the Calvin cycle of photosynthesis. It serves as a key substrate in the conversion of carbon dioxide into organic compounds within plant cells.
Stereochemistry: Stereochemistry is the study of the three-dimensional arrangement of atoms in molecules and how this arrangement affects the chemical and physical properties of the substance. It examines the spatial orientation of atoms and their relationship to one another, which is crucial in understanding many organic chemistry concepts.
Stereoisomers: Stereoisomers are molecules that have the same molecular formula and connectivity, but differ in the three-dimensional arrangement of their atoms in space. This spatial arrangement of atoms leads to different physical and chemical properties, even though the atoms are connected in the same way.
Talose: Talose is a rare aldose sugar that belongs to the family of monosaccharides. It is one of the eight stereoisomeric forms of the hexose sugars and is closely related to the more common sugars like glucose and galactose.
Tetrose: A tetrose is a monosaccharide, or the simplest type of carbohydrate, that contains four carbon atoms. Tetroses are an important class of carbohydrates that are relevant in the context of classifying carbohydrates and understanding the configurations of aldoses.
Triose: A triose is a simple sugar or monosaccharide containing three carbon atoms. Trioses are an important class of carbohydrates that serve as building blocks for more complex sugars and play a crucial role in various metabolic pathways.
Xylose: Xylose is a monosaccharide, or simple sugar, that is classified as an aldose. It is a pentose sugar, meaning it has five carbon atoms, and it is found naturally in plant materials like wood, straw, and corn cobs. Xylose is an important component in the context of understanding the configurations of aldoses and the eight essential monosaccharides.
© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
Back
Practice QuizGlossary
Practice QuizGlossary
Next guide