Naming Monosaccharides Quiz

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Questions and Answers

What distinguishes aldoses from ketoses?

Aldoses contain a ketone group while ketoses contain an aldehyde group.

Aldoses and ketoses both contain a carboxylic group.

Aldoses contain an aldehyde group while ketoses contain a ketone group. (correct)

Both aldoses and ketoses contain identical structural formulas.

Which term describes monosaccharides with four carbon atoms?

Pentoses

Hexoses

Trioses

Tetroses (correct)

What is the classification of glucose?

Ketotriose

Aldopentose

Aldohexose (correct)

Ketopentose

Which process forms the ring structure of sugars from an aldehyde group?

Condensation reaction between the aldenol group and hydroxyl group. Signup and view all the answers

Which of the following represents a hexose?

Fructose Signup and view all the answers

What are aldotrioses?

Monosaccharides with three carbon atoms and aldehyde groups. Signup and view all the answers

What is the characteristic structure of pyranose?

A six-membered ring. Signup and view all the answers

What determines if a sugar is classified as an α-sugar or a β-sugar?

The position of the remaining hydroxyl group in the ring structure. Signup and view all the answers

What term describes the 1-4 ring form that resembles an organic compound called furan?

Glucofuranose Signup and view all the answers

What type of carbon atom is known as an asymmetric carbon atom?

A carbon atom bonded to four different groups Signup and view all the answers

Which statement about optical isomerism is correct?

It involves compounds that are mirror images of each other. Signup and view all the answers

What is the formula to determine the number of isomers for a substance containing asymmetric carbon atoms?

2n Signup and view all the answers

Which of the following chemically signifies D and L isomers?

The spatial arrangement of atoms Signup and view all the answers

What is the anomeric carbon in an aldose sugar?

Carbon number 1 Signup and view all the answers

What is mutarotation in the context of optically active substances?

A gradual change of specific rotation Signup and view all the answers

What is the specific rotation of β-glucose when freshly dissolved in water?

+19 Signup and view all the answers

Study Notes

Naming Monosaccharides

Monosaccharides can be named based on the presence of an aldehyde or ketone group
Aldoses: Monosaccharides containing an aldehyde group (-CHO). The suffix "-ose" generally means sugar.
Ketoses: Monosaccharides containing a ketone group (-C=O).
Monosaccharides can also be named based on the number of carbon atoms they contain:
Trioses: 3 carbon atoms
Tetroses: 4 carbon atoms
Pentoses: 5 carbon atoms
Hexoses: 6 carbon atoms
Heptoses: 7 carbon atoms
To classify monosaccharides fully, both the presence of the aldehyde or ketone group and the number of carbon atoms are used:
Aldotrioses and ketotrioses
Aldotetroses and ketotetroses
Aldopentoses and ketopentoses
Aldohexoses and ketohexoses

Classification of Monosaccharides

Trioses:
- Aldotrioses: Glyceraldehyde (glycerose), the "parent" sugar
- Ketotrioses: Dihydroxyacetone
Tetroses:
- Aldotetroses: Erythrose
- Ketotetroses: Erythrulose
Pentoses:
- Aldopentoses: Ribose, arabinose, xylose, and lyxose
- Ketopentoses: Ribulose and xylulose
Hexoses:
- Aldohexoses: Glucose, galactose, and mannose
- Ketohexoses: Fructose

Ring (Cyclic) Structures of Sugars

Simple open-chain formulas for sugars don’t explain reactions like the inability of glucose to react fully like an aldehyde. This suggests the aldehyde group is “masked” in some way.
In solution, sugars with aldehyde groups undergo these transformations:
- Hydration: The aldehyde group is hydrated to form an aldenol group (alcohol).
- Condensation: The -OH of the aldenol group condenses with the -OH on C4 or C5 to form a ring structure (hemiacetal structure).
- α or β form:
  - If the remaining -OH is on the right side, it’s an α-sugar.
  - If the remaining -OH is on the left side, it’s a β-sugar.

Pyranose and Furanose

The 1-5 ring form is called pyranose because it resembles pyran (e.g., α and β glucopyranose).
The 1-4 ring form is called furanose because it resembles furan (e.g., α and β glucofuranose).

Asymmetric Carbon Atoms

An asymmetric carbon atom is attached to four different groups or atoms.
Compounds with asymmetric carbons, known as chiral centers, exhibit two properties:
- Optical Activity: They rotate the plane of polarized light.
  - (ɗ) or (+) = dextrorotatory, rotates the plane of polarized light to the right.
  - (ℓ) or (-) = levorotatory, rotates the plane of polarized light to the left.
- Optical Isomerism: They can exist in more than one form (isomers).

Speciﬁc Rotation

For a fixed concentration and tube length, the angle of rotation depends only on the substance. This is called specific rotation.
The specific rotation is measured in degrees when the concentration is 100g/dL, the tube length is 10 cm, and sodium light at 20°C is used. For example, glucose has a specific rotation of (+52.5), and fructose has (-91).

Optical Isomerism

A substance with one asymmetric carbon atom has two isomers.
A substance with two or more asymmetric carbon atoms can exist in a number of isomers calculated by 2^n, where n is the number of asymmetric carbons.
For example, glucose has four asymmetric carbons, resulting in 16 possible isomers.

D and L Isomers (Enantiomers)

Enantiomers are mirror images of each other.
They have the same structural formula but differ in their spatial configuration. They rotate polarized light equally but in opposite directions.
Glyceraldehyde, the simplest monosaccharide, has one asymmetric carbon and two optical forms: L and D forms.
D and L forms are classified based on the position of the -OH group attached to the carbon next to the last -CH2OH. For example, using carbon number 5 in glucose.

Anomeric Carbon and Anomers

Anomeric carbon: The asymmetric carbon formed from the active carbonyl sugar group – carbon number 1 in aldoses and carbon number 2 in ketoses.
Anomers: Isomers formed by changing the position of the -OH group attached to the anomeric carbon. For example, α and β glucose are two anomers.

Mutarotation

Mutarotation is the gradual change in specific rotation of an optically active substance with a free aldehyde or ketone group.
For example:
- Freshly dissolved α-glucose in water has a specific rotation of +112.
- Freshly dissolved β-glucose in water has a specific rotation of +19.

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Description

Test your knowledge on the classification and naming of monosaccharides! This quiz covers both aldehyde and ketone groups as well as the number of carbon atoms. Review important terms like aldoses, ketoses, and various carbon classifications.