Organic synthesis Flashcards
What are isomers
Isomers are molecules with the same molecular formula but a different arrangement of the way in which the atoms are joined together (i.e. a different structure).
What is chain isomerism
This is when the main carbon chain (sometimes known as the parent chain) of a molecule is shortened and extra carbon and hydrogens are present as a ‘branch’ from the main chain.
What is positive isomerism
This is when the functional group of a molecule moves to a different position on the chain. This can affect both alkenes (when the double bond moves) and alcohols (when the -OH group moves).
What rules to follow to work out the name of complex molecules
1) Identify the longest continuous chain of carbon atoms. This is the main chain and will give you the basis of the molecule’s name (for example, a five carbon chain will give you - pent - as part of the name).
2) rIdentify the functional group of the molecule.
OH group for alcohols. This means the name will end in -anol.
C=C group for alkenes. This means the name will end in -ene.
If none of the above groups are present, then it is an alkane and will end in -ane.
3) Identify any carbon side chains. These will be either methyl (-CH3) or ethyl (-CH2CH3) groups and will go at the front of the name in alphabetical order.
4) Number the carbons in the main chain, starting from the end that has the functional group closest to it.
5) Put numbers in front of each group according to the number of the carbon that it is attached to.
Note that if a position number is needed for an alcohol group, the number is put between the –an- and the –ol of the name. For example, butan-1-ol.
