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flashcards on achiral, chiral, and stereomolecules

QuestionAnsweranswer cont.
What is Chiral/Achiral How do you distinguish between the two? Chiral: mirror images of a molecule are not superimposable, doesn't always have a stereocenter, NO PLANE OF SYMMETRY Achiral: mirror images of a molecule are superimposable, PLANE OF SYMMETRY Test superimposability or see if it has a plane of symmetry all planar molecules are achiral
what are enantiomers, diastereomers and meso compounds enantiomers: must be chiral, mirror image pairs diastereomers: not superimposable, not mirror images meso compounds: has two or more stereocenters but is superimposable with mirror image all meso compounds are achiral meso compounds can be spotted due to their internal plane of symmetry
How do you identify stereocenters in a chiral molecule? what is a racemic mixture? it is attached to 4 DIFFERENT groups a racemic mixture: A + its enantiomer = 50/50
What is the difference between identical, structural isomers, conformers, and stereoisomers identical: exactly the same structural: same molecular formula, different structural formula conformers: different rotations of same molecular structure stereoisomers: atoms connected same, different spatial structure, ie. diastereomers and enant
Cahn, Ingold, Prelog rules to assign substituents 1. higher atomic number = higher priority and vice versa 2.if same A.N., go down chain to first point of difference, the one w attached to more things besides H, is higher priority 3.double and triple bonds treated as single bonds and expanded
What is one way to assign R/S? Version 1 1.rank substituents by priority 2.rotate until lowest, usually H, is farthest away 3.determine if the ranking progression is clockwise(R) or counter clockwise(S).
What is the other way to assign R/S? Version 2 1. rank substituents by priority 2. place thumb along stereocenter bond 3. see which hand, when curled gives 1,2,3 progression. Right means R, left means S
how do you compare relationships in more complex structures? use R/S if all the r's switch to s's and vice versa, it's an enantiomer if some r's switch to s's or vice versa, its a diastereomer if you invert a stereocenter, the R/s switches
what happens with halgenation of different parts of an alkane if you halogenate a substituent, it remains active as long as the stereocenter is left intact halogenation of a stereocenter leads to a racemic mixture
based on the relationship between two stereoisomers as diastereomers or enantiomers, what will their physical properties be like? bond length increases and strength decreases as you move down the pd table when bonded to a halogen bc of the mismatch but enantiomers, because they are the similar , mirror images, have the same properties. and diastereomers, because they are different, not superimposable or mirror images, have different properties
Created by: hsinha93