unit 2a: stereochemistry Flashcards
two types of isomers
structural isomers, stereoisomers
two types of stereoisomers
geometric, optical
structural isomers
when the atoms are bonded together in a different order
stereoisomerism
when the atoms are connected in the same way and in the same order however are arranged differently in 3D space
geometric isomers occur in
molecules containing a C=C double bond as there is no free rotation of the groups of atoms around a double bond, only occurs when there are different groups each side of the double bond
two types of geometric isomers
cis- when the groups are on the same side of the double bond, trans- when the groups are on opposite sides of the double bond
boiling points of geometric isomers
cis isomers tend to have higher boiling points as they tend to be more polar, symmetry in trans isomers cancels out polarity
chemical properties of geometric isomers
occasionally cis and trans isomers can have different chemical properties
geometric isomers and cyclic compounds
geometric isomerism can arise in cyclic compounds where rotation around the C-C single bonds is restricted due to the ring structure
optical isomers occur in
a molecule that contains a tetrahedral carbon atom that has four different groups attached (a chiral carbon)
chiral carbon
a tetrahedral carbon atom with four different groups attached, these can exist in two isomeric forms
optical isomers are
non-superimposable mirror images of each other called enantiomers
physical properties of optical isomers
they have identical physical properties, except for their effect on plane polarised light
optical isomers and plane polarised light
one isomer will rotate the light in a clockwise direction and the other will rotate it in an anticlockwise direction. light is rotated by the same amount although different directions
optically active substances
substances that can rotate plane polarised light
