Organic Chemistry
Diastereomers are any set of stereoisomers that are not enantiomers, such as molecules with multiple stereocenters in which some centers are inverted and others are not, or cis and trans isomers. A meso compound is a compound that contains both multiple chiral centers and an internal mirror plane of symmetry, making them achiral despite having chiral centers.
Fischer projections are used to visualize three-dimensional compounds in 2D, with vertical axis bonds pointing away and horizontal axis bonds coming towards the viewer. Rotating a Fischer projection by 90 degrees or swapping any two groups creates its enantiomer, while rotating it by 180 degrees or swapping groups twice regenerates the same molecule. Lastly, when it comes to optical activity, optically inactive reagents will produce optically inactive products, meaning if all reagents are achiral or racemic, the product will also be achiral or racemic.
Lesson Outline
<ul> <li> Diastereomers <ul> <li>Definition: any two stereoisomers that aren't enantiomers</li> <li>Enantiomers: non-superimposable mirror images</li> <li>Diastereomers examples: trans and cis isomers</li> <li>Diastereomers with multiple chiral centers</li> </ul> </li> <li> Meso Compounds <ul> <li>Definition: compounds with multiple chiral centers and an internal mirror plane of symmetry</li> <li>Achiral despite containing chiral centers</li> </ul> </li> <li> Fischer Projections <ul> <li>Viewing 3D molecules in a 2D plane</li> <li>Creating Fischer projections: orientation, vertical and horizontal axis rules</li> <li>Comparison with 3D depictions</li> <li>Rotating Fischer projections or swapping groups: generates enantiomers</li> </ul> </li> <li> Optical Activity Principle <ul> <li>In order to form an optically active product, you need optically active starting materials or reagents</li> <li>Optically inactive reagents result in optically inactive products</li> <li>Chiral and optically inactive: 50/50 racemic mixture of enantiomers</li> </ul> </li> </ul>
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FAQs
Diastereomers and enantiomers are two types of stereoisomers, which are molecules that have the same molecular formula and connectivity of atoms but differ in the three-dimensional orientation of their atoms in space. Diastereomers are stereoisomers that have opposite configurations at one or more, but not all, chiral centers. They often have different physical properties and chemical reactivities. Enantiomers are stereoisomers that are non-superimposable mirror images of each other and have the same physical and chemical properties, except for their optical activity. Both diastereomers and enantiomers are important concepts in stereochemistry, as they affect the structure-function relationship, biological activity, and properties of compounds.
Meso compounds are a special category of stereoisomers that have multiple chiral centers but exhibit achiral properties, which means they lack optical activity. This occurs because the compound contains a plane of symmetry that leads to the existence of equal and opposite chiral centers, resulting in a net cancelation of the optical activities. Meso compounds are different from other stereoisomers, such as enantiomers and diastereomers, in that they are not optically active and do not have an enantiomer.
Fischer projections are a convenient way to represent the three-dimensional stereochemical arrangement of chiral centers in a molecule using a two-dimensional drawing. In a Fischer projection, the molecule is represented as a simple cross, with horizontal lines representing bonds pointing towards the viewer and vertical lines representing bonds pointing away from the viewer. This allows for easy visualization of the R/S configurations around each chiral center and facilitates comparing and analyzing the relationships between different stereoisomers. Fischer projections are especially useful in illustrating the stereochemistry of carbohydrates, amino acids, and other biomolecules with multiple chiral centers.
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