DF - isomerism Flashcards
General formula
a formula that can describe any member of a family of compounds
eg. CnH2n+1OH for alcohols
Molecular formula
the actual no. of atoms of each element in a molecule
eg. C2H10O
Shortened structural formula
shows the atoms, carbon by carbon, with the attached hydrogens and functional groups
Structural formula
shows how all the atoms are arranged and all the bond between them
Skeletal formula
shows the bonds of the carbon skeleton only, with any functional groups
the hydrogen and carbon atoms are not shown
what is structural isomerism?
structural isomers have a different structural arrangement of atoms
- the atoms are connected in different ways but still have the same molecular formula
what are the 3 types of structural isomers?
- different carbon skeleton
- functional group in different place
- different functional groups
different carbon skeleton - explain and effects
the carbon skeleton can be arranged differently
eg. as a straight chain or branched - butane and methylpropane
have similar chemical properties but physical properties, like boiling point, will be different because of the change of shape in the molecule
functional group in different place - explain and effects
the skeleton and functional group could be the same only with the functional group attached to a different carbon atom
eg. butan-1-ol and butan-2-ol
different physical properties and the chemical properties might be different too
eg. primary, secondary and tertiary alcohols
different functional groups - explain and effects
the same atoms can be arranged into different functional groups
eg. butan-1-ol and ethoxyethane
they will have very different physical and chemical properties
Is there rotation around C=C double bonds?
No
doubles bonds are rigid and don’t bend much either
Is there rotation around C-C single bonds?
Yes
C-C bonds rotate freely - like wheels on an axis
What is Stereoisomerism?
Stereoisomers have the same shortened structural formula but a different arrangement in space
What causes stereoisomerism?
the lack of free rotation around the C=C double bond
What are the types of stereoisomerism? - explain them
Z-isomers and E-isomers
- Z-isomers (cis) - the same side, the hydrogens are either both below or both above the plane
- E-isomers (trans) - across, the hydrogens are not on the same side
if no hydrogens - cis/trans is used, looks for the same groups.