Summary
Summary Summaries CMY 127
- Course
- Cmy 127
- Institution
- University Of Pretoria (UP)
Summaries based off the textbook and class notes
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THEME 2: SATURATED HYDROCARBONS AND CONFORMATIONSTRUCTURAL ISOMERISM IN ALKANES
‐ Alkanes are saturated hydrocarbons
o Straight chain or branched chain alkanes have formula CnH2n+2
o Cyclic alkanes have 2 H’s fewer than the max for each ring
‐ Conformers: molecules can fold into different 3-dimensional arrangements but
remain the same molecule
‐ Structural (constitutional) isomers: 2 different compounds with the same molecular
formula
‐ There are 5 structural isomers for C6H14
‐ The number of structural isomers increases with the size of the alkane
‐ Saturated C’s are classified as primary (1o), secondary (2o), tertiary (3o) or quaternary
(4o) according to the number of attached C groups → rather use names over symbols
IUPAC NAMING OF ORGANIC COMPOUNDS
‐ Names of straight chain alkanes indicate the carbon number and end in -ane
NUMBER OF CARBONS PARENT
1 Meth-
2 Eth-
3 Prop-
4 But-
5 Pent-
6 Hex-
7 Hept-
8 Oct-
9 Non-
10 Dec-
‐ Branched chain alkanes must be named according to the longest chain (parent
chain), and the substituents
‐ A substituent is named according to the alkane it would have been
o Methyl (Me)
o Ethyl (Et)
o Propyl (Pr)
o Butyl (Bu)
‐ R- is used as the abbreviation to imply any random alkyl group (any hydrocarbon
group)
, NAMING BRANCHED ALKANES
1. Find the parent chain
o Choose the longest continuous carbon chain, with the most substituents
2. Number the atoms in the main chain
o Begin at the end, nearest to a branch
3. Name and number the substituents
o Group identical substituents and use the prefixes → di-, tri-, tetra- etc.
4. Write the complete name
o Arrange the substituents in alphabetical order
o Add the parent and functional group suffix (-ane)
‐ Separate numbers by commas and separate numbers from letters by hyphens →
take note there are no spaces in the name of an alkane
NAMES OF BRANCHED ALKYL GROUPS (NB!!)
‐ Sometimes the alkyl group is branched, there are 4 common branched alkyl groups
with their own names
‐ Every organic molecule must have its own IUPAC name even if the structural
drawings look different
CYCLOALKANES (CnH2n)
‐ A saturate hydrocarbon that contains C-atoms bonded to form a ring
‐ Five-membered (cyclopentane) and six-membered (cyclohexane) rings are abundant
in nature
IUPAC NAMES
‐ Named as a cycloalkane according to the C atoms in the ring, unless there is a longer
side chain, then it becomes a cycloalkyl substituent
o If only one substituent then no need to give it a number
o Number the C’s of the ring to ger the lowest possible set of numbers (i.e. if
you can number in multiple ways then use the smaller set)
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