Isomers are molecules with the same molecular formula but different arrangements of atoms. This means that isomers have the same number of atoms of each element, but the atoms are arranged differently in space. Isomers can have different physical and chemical properties, even though they have the same molecular formula.
Define isomers Explain
stereo isomerism and optical isomerism of monosaccharides in detail
Stereoisomers
are isomers that have the same structural formula but differ in the way that
their atoms are arranged in three-dimensional space. Stereoisomers arise from
the existence of chiral centers, which are carbon atoms with four different
groups attached to them. Stereoisomers can be further classified into two
types: enantiomers and diastereomers.
Optical
isomers, also known as enantiomers, are a type of stereoisomerism that occurs
when two molecules are mirror images of each other and cannot be superimposed.
Optical isomers have identical physical and chemical properties except for
their interaction with plane-polarized light. Enantiomers rotate the plane of
polarized light in opposite directions, and this property is used to
distinguish them from each other.
Monosaccharides
are simple sugars that cannot be hydrolyzed into smaller molecules. They have
the general formula (CH2O)n, where n can range from 3 to 7. Monosaccharides are
classified based on the number of carbon atoms they contain. For example,
trioses have three carbon atoms, tetroses have four carbon atoms, and so on.
Stereoisomerism
occurs in monosaccharides when one or more of the carbon atoms in the molecule
has four different groups attached to it. For example, in the case of glucose,
which is a hexose sugar, the carbon atom at position 5 (C-5) has four different
groups attached to it. This carbon atom is called a chiral center, and it gives
rise to two stereoisomers: D-glucose and L-glucose.
D-glucose and
L-glucose are mirror images of each other and are therefore enantiomers. They
have the same physical and chemical properties except for their interaction
with plane-polarized light. D-glucose rotates the plane of polarized light to
the right, while L-glucose rotates the plane of polarized light to the left.
Optical
isomerism is an important concept in biochemistry, as many biological molecules,
including proteins and DNA, are chiral and interact selectively with one
enantiomer over the other. Therefore, the ability to distinguish between
enantiomers is essential for understanding the biological activity of these
molecules.
Isomers are molecules
that have the same molecular formula but different structural arrangements of
atoms. In other words, isomers have the same number of atoms of each element,
but the atoms are arranged differently in space. Isomers can have different
physical and chemical properties, even though they have the same molecular
formula. There are different types of isomers, including structural isomers,
stereoisomers, and geometric isomers, each characterized by a specific type of
difference in their structural arrangement.
Stereoisomerism
is a type of isomerism where two or more compounds have the same molecular
formula and sequence of bonded atoms, but differ in their spatial arrangement
due to the presence of chiral centers. Stereoisomers of monosaccharides, which
are the simplest forms of carbohydrates, are of two types: optical isomers or
enantiomers, and diastereomers.
Optical
isomers, also known as enantiomers, are a special type of stereoisomerism that
occurs when two molecules are non-superimposable mirror images of each other,
i.e., they have the same chemical formula and connectivity but different
three-dimensional orientation of their constituent atoms. Enantiomers have the
ability to rotate the plane of plane-polarized light in equal amounts but in
opposite directions. This property is known as optical activity and is used to
distinguish between the two enantiomers. In the context of monosaccharides,
optical isomerism arises due to the presence of a chiral carbon atom, i.e., a
carbon atom bonded to four different substituent groups. For example, D-glucose
and L-glucose are enantiomers of glucose.
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Diastereomers,
on the other hand, are stereoisomers that are not mirror images of each other
and have different physical and chemical properties. They can differ in terms
of their stereochemistry at one or more chiral centers, but not all. In
monosaccharides, diastereomers arise when two or more chiral centers are
present, and their configurations are different in the two molecules. For
example, glucose and fructose are diastereomers of each other, differing in
their stereochemistry at C2, C3, and C4.
The optical
isomerism of monosaccharides is of great significance in biology as it affects
their interaction with other molecules in the cell. For instance, only one of
the enantiomers of a particular sugar may be metabolized by an enzyme, while
the other enantiomer may not be recognized. This selectivity is an important
aspect of molecular recognition, which is a fundamental process in
biochemistry. Moreover, carbohydrates play important roles in the body,
including energy storage and cell signaling, and the specific properties of
optical isomers can impact these functions.
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