University:
Eastern Kentucky University
Course:
CHE 361 | Organic Chemistry I
Academic year:

2020
Views:

85

Pages:

1
Author:

Oerallerxhcq

Organic Chemistry 2: Isomer Structural Isomers Relative & Absolute Configuration • Share only a molecular formula. • Have different physical and chemical properties. Stereoisomers Relative Configuration: Gives the stereochemistry of a compound in comparison to another compound. E.g. D and L. Compounds with atoms connected in the same order but differing in 3D orientation. Chiral Center: Four different groups attached to a central carbon. 2n Rule: 𝑛=#$of$chiral$centers #$of$stereoisomers=23 Absolute Configuration: Gives the stereochemistry of a compound without having to compare to other compounds. E.g. S and R. Cahn-Ingold-Prelog Priority is given by looking at atoms connected to Priority Rules: the chiral carbon or double-bonded carbons; whichever has the highest atomic # gets highest priority. (Z) and (E) for Alkenes: (Z): Highest priority on same side. (E): Highest priority on opposite sides. Conformational Isomers (R) and (S) for A stereocenter’s configuration is determined by Stereocenters: putting the lowest priority group in the back and drawing a circle from group 1-2-3. (R): Clockwise (S): Counterclockwise Anti Gauche Eclipsed Fischer Projection: Vertical lines go to back of page (dashes); horizontal lines come out of the page (wedges). Differ by rotation around a single (s) bond Cyclohexane Equatorial: In the plane of the molecule. Substituents: Axial: Sticking up/down from the molecule’s plane. Configurational Isomers Altering Fischer Switching 1 pair of substituents inverts the Projection: stereochemistry; switching 2 pairs retains stereochemistry. Rotating entire diagram 90° inverts the stereochemistry; rotating 180° retains stereochemistry. Enantiomers Enantiomers: Nonsuperimposable mirror images. Opposite stereochemistry at every chiral carbon. Same chemical and physical properties, except for rotation of plane polarized light. Optical Activity: The ability of a molecule to rotate plane-polarized light: d- or (+) = RIGHT, l- or (-) = LEFT. Racemic Mixture: 50:50 mixture of two enantiomers. Not optically active because the rotations cancel out. Meso Compounds: Have an internal plane of symmetry, will also be optically inactive because the two sides of the molecule cancel each other out. Diastereomers Diastereomers: Stereoisomers that are NOT mirror image. Cis-Trans: A subtype of diastereomers. They differ at some, but not all, chiral centers. Different chemical and physical properties.