Stereochemistry Flashcards
what is an isomer?
isomers are molecules with the same molecular formula but different structural formula
what are the two main types of isomers?
structural isomers
stereoisomers
what are structural isomers?
structural isomers have the same molecular formula but differ in the order in which atoms are bonded together
what are stereoisomers?
stereoisomers have the same molecular formula and bonding order, but their atoms are arranged differently in space
what are the two types of stereoisomers?
geometric
optical
what causes geometric isomerism?
geometric isomers occur when there is restricted rotation around a C=C double bond or a C-C single bond in a cyclic compound
what conditions are needed for geometric isomerism to occur?
two different groups must be attached to each carbon involved in the double bond or cyclic structure
how are geometric isomers labeled?
cis isomer - both groups are on the same side of the C=C bond
trans isomer - both groups are on opposite sides of the C=C bond
how do geometric isomers differ in properties?
they have different physical properties and different chemical properties
examples of physical and chemical properties
physical - melting and boiling point
chemical - dehydration reactions
what causes optical isomerism?
optical isomerism occurs in compounds with a chiral carbon
what is a chiral carbon atom?
it has four different groups attached in a tetrahedral arrangement
what are optical isomers also called?
enantiomers
what are the key characteristics of optical isomers?
they are asymmetric
they are non-superimposable mirror images of each other
how do optical isomers differ in properties?
they have identical physical and chemical properties except,
they rotate plane-polarised light in opposite directions
they may behave differently in chiral environments, such as biological systems
what is plane polarized light?
light that vibrates in only one plane after passing through a polarizer
how do optical isomers affect plane polarized light?
one isomer rotates light in one direction
the other isomer rotates light by the same amount but in the opposite direction
what is a racemic mixture?
a mixture containing equal amounts of both optical isomers, making it optically inactive because their effects cancel out
