Chapter 5 - Stereochemistry Flashcards
What are the two major classes of isomers?
Constitutional Isomers and Stereoisomers
Define Configuration
a particular three-dimensional arrangement
What is the major difference between constitutional and structural isomers?
they have different IUPAC names
What is the major difference between two stereoisomers?
they have the same IUPAC name (cis/trans may differ) and only differ in the way the atoms are oriented in space
Define Constitutional Isomer
different order of connections that gives a different carbon backbone and/or different functional groups
Define Stereoisomers
same connection, different spatial arrangement of atoms
What are the two different types of Stereoisomers?
Enantiomers: mirror images
Diastereomers: all other stereoisomers (includes cis, trans, and configurational)
Define Chiral
a mirror-image molecule that is NOT the same when superimposed and contain a stereogenic center (ex: hands are stereoisomers and chiral)
Define Achiral
a mirror-image molecule that is the same when superimposed and usually contain a plane of symmetry (ex: a flask is a stereoisomer and achiral)
Define Enantiomers
a mirror-image molecule that is non-superimposable
this makes it a chiral molecule and an enantiomer
What groups can we omit when looking for stereogenic centers?
CH2 groups
CH3 groups
double bonded carbons
triple bonded carbons
What is the main characteristic to look for in the search for stereogenic carbons?
All 4 bonded groups on a carbon atom must be DIFFERENT
no stereogenic carbons = achiral molecule
R-enantiomers rotate which direction?
Clockwise
S-enantiomers rotate which direction?
Counterclockwise
What are the rules to assigning priorities for stereogenic carbons?
1 - highest priority to highest atomic number
2 - “tie” sends priority to atom of first difference with higher atomic number
3 - highest priority to isotope of larger mass
4 - “break” multiple bonds to assign priorities
lowest priority atom always goes in the back
