User:GreyAvocado/Stereochemistry

Definitions

Optical Activity:

• Definition: Optical activity is the ability of a chiral molecule to rotate plane-polarized light.
• Explanation: When plane-polarized light passes through a solution containing a chiral compound, the plane of light is rotated either clockwise or counterclockwise. The degree of rotation is specific to each enantiomer and can be used to distinguish between the two.
• Measurement: This is measured using a polarimeter, with the direction of rotation described as dextrorotatory (+) or levorotatory (-).

Types (delete?)

• Atropisomerism An energetic form of axial chirality. This form of chirality derives from differential substitution about a bond, commonly between two sp²-hybridized atoms.
• Cis–trans isomerism Also referred to as geometric isomers, these compounds have different configurations due to the inflexible structure of the molecule. Two requirements must be met for a molecule to present cis-trans isomerism: 1. Rotation within the molecule must be restricted. 2. Two nonidentical groups must be on each doubly bonded carbon atom.
• Conformational isomerism This form of isomerism is also referred to as conformers, rotational isomers, and rotamers. Conformational isomerism is produced by rotation about the Single bond.
• Diastereomers These stereoisomers are non-image, non-identical. Diastereomers occur when the stereoisomers of a compound have differing configurations at corresponding stereocenters.
  • Example: Threonine and erythrose are diastereomers of each other. They have similar structures but cannot be mirror images due to the multiple chiral centers.
• Enantiomers A pair of chiral molecules that are non-superimposable mirror images of each other.
  • Example: The two enantiomers of the drug ibuprofen are (R)-ibuprofen and (S)-ibuprofen, with only the (S)-form active in reducing inflammation and pain.
• Epimers:
  • Definition: Epimers are a type of diastereomer that differ in configuration at only one chiral center.
  • Explanation: They are commonly found in sugar chemistry, where two sugars can differ by the configuration of a single carbon atom.
  • Example: Glucose and galactose are epimers, differing only at the C-4 position in their structure.

Catalogue of Stereoisomers

Atropisomers

Atropisomerism is an energetic form of axial chirality. This form of chirality derives from the inability to rotate about a bond, due to steric hindrance between functional groups, commonly between two sp²-hybridized Carbon atoms.

Atropisomer pair example

Cis-Trans isomers

Cis-Trans isomers, also referred to as geometric isomers, have different configurations due to the inflexible structure of the molecule, usually an alkene double bond. Two requirements must be met for cis-trans isomerism:

1. Rotation within the molecule must be restricted.

2. Two nonidentical groups must be on each doubly bonded carbon atom.

Cis-trans isomer pair example

Conformational isomers

Conformational isomerism pairs are also referred to as conformers, rotational isomers, and rotamers. Conformational isomerism is produced by rotation about the Single bond. Conformers are differentiated by energy differences. The example below shows the eclipsed (left) and staggered (right) conformations of the same molecule.

Conformational isomer pair example

Diastereomers

Diastereomers are non-superimposable, non-identical stereoisomers. Diastereomers occur when the stereoisomers of a compound have differing (R)/(S) configurations at some, but not all corresponding stereocenters.

• Example: Threonine and erythrose are diastereomers of each other. They have similar structures but cannot be mirror images due to the multiple chiral centers.
• Example: The below pair can also be classified as epimers.

Diastereomer pair example

Enantiomers

Enantiomers are a pair of chiral molecules that are non-superimposable mirror images of each other. Enantiomers occur when the stereoisomers of a compound have differing (R)/(S) configurations at all corresponding stereocenters.

• Example: The two enantiomers of the drug ibuprofen are (R)-ibuprofen and (S)-ibuprofen, with only the (S)-form active in reducing inflammation and pain.

Enantiomer pair example

Epimers

Epimers are a subcategory of diastereomers that differ in (R)/(S) configurations at only one corresponding stereocenter. They are commonly found in sugar chemistry, where two sugars can differ by the configuration of a single carbon atom.

• Example: D-glucose and D-galactose are epimers, differing only at the C-4 position in their structure. (see sugar numbering)

Epimer pair example

Grammar fixes:

• "that forms the structure of molecules" → "that form the structure of molecules"

• "which by definition" → "which are defined as having the same molecular formula and sequence of bonded atoms (constitution) but differing in the geometric positioning of the atoms in space."
• "the effect on the physical or biological properties these relationships impart upon the molecules in question" → "the effects these relationships have on the physical or biological properties of the molecules."
• "the manner in which these relationships influence the reactivity of the molecules in question"→"and how these relationships affect the reactivity of molecules.
• Kekulé used tetrahedral models earlier in 1862 but never published these → Kekulé explored tetrahedral models earlier, in 1862, but never published his work
• Arthur Robertson Cushny, Scottish Pharmacologist, in 1908, first offered a definite example → Arthur Robertson Cushny, a Scottish pharmacologist, first provided a clear example in 1908...
• allowing the relative position of these atoms in the molecule to be described unambiguously → ...allowing unambiguous descriptions of their relative positions in the molecule.
• Thalidomide example → Thalidomide Example
• Some of the several proposed mechanisms of teratogenicity involve a different biological function for the (R)- and the (S)-thalidomide enantiomers. → Several proposed mechanisms of teratogenicity involve different biological functions for the (R)- and (S)-thalidomide enantiomers.
• In the human body however, thalidomide undergoes racemization → In the human body, however, thalidomide undergoes racemization
• developmental deformations → developmental deformities

References

• Chemdraw (RRID:SCR_016768)
• Moss, G. P. (2016). Basic Terminology of Stereochemistry [dataset]. In IUPAC Standards Online. De Gruyter. https://doi.org/10.1515/iupac.68.3330
  • Lists most of the relative terminologies. Very useful
• Petersen, Q. R. (1966). Introduction to stereochemistry (Mislow, Kurt). Journal of Chemical Education, 43(3), A272. https://doi.org/10.1021/ed043pa272.2
  • One of the earliest publications on stereochemistry, foundation of many other researches. Useful.
• Crouch, R. D. (2002). Stereochemistry (Morris, David G.). Journal of Chemical Education, 79(2), 167. https://doi.org/10.1021/ed079p167.1
  • Author assumes readers have no prior knowledge on stereochemistry, fits well for this project. Very useful.