Chapter 2: Isomers Flashcards
what are structural isomers
share only the molecular formula; different chemical and physical properties
what are conformational isomers
differ by rotation around sigma bond
what are staggered conformations
60 degrees apart
what are anti staggered conformations
two largest groups 180 degrees apart; strain minimized
what are gauche conformations
two largest groups 60 degrees apart
what are eclipsed conformations
groups directly in front of each other
what are totally eclipsed conformations
two largest groups in front of each other; strain maximized
what is angle strain
stretching or compressing angles from their normal size
what is nonbonded strain
interactions between substituents attached to non adjacent carbons
what is axial position
sticking up or down from plane of molecule; more strain
what is an equatorial position
in the plane of the molecule; less strain
what are configuration isomers
can only be interchanged by breaking and reforming bonds
what are enantionmers
nonsuperimposable mirror images; opposite stereochemistry at every chiral carbon; same chemical and physical properties
what are racemic mixtures
equal concentrations of two enantiomers rotations that cancel one another out
what are meso compounds
internal plane of symmetry ; optically inactive
what are diastereomers
non-mirror images; differ at some but not all chiral centers; different chemical and physical properties
what are cis-trans isomers
subtype of diastereomer in which groups differ in position about an immovable bond
what is relative configuration
gives the stereochemistry of a compound in comparison to another
what is a chiral center
carbon with four DIFFERENT groups attached
what is absolute configuration
gives stereochemistry without having to compare; uses Cahn-Ingold-Prelog Priority rules
what is a Z alkene
highest priority substituents on same side of double bond
what are the Cahn-Ingold-Prelog Priority rules
highest atomic number = highest priority
what is an E alkene
highest priority groups on opposite sites of double bond
how is stereochemistry determined
lowest priority group in the back; draw circle from group 1 to 2 to 3; if circle is clockwise (R); If circle is counterclockwise (S)
what are the lines in fisher projections
vertical –> dashes
horizontal –> wedges