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Naming Alkenes, Alkynes, and Cyclics
Carbon can form 4 bonds due to its 4 valence electrons
Alkenes: contains at least one carbon-carbon double bond Suffix -ene
Alkynes: contains at least one carbon-carbon triple bond Suffix -yne
Contain less hydrogen than the alkanes because two (alkenes) or three (alkynes) of a carbon’s bonds are used for double or triple bonds
Since they contain less than the maximum quantity of H, they are referred to as unsaturated Whereas alkanes are saturated with the maximum
number of H’s per carbon
There are a few changes to the naming rules. 1. The name ends in –ene 2. The main chain must contain both carbon
atoms of the double bond (even if a longer chain is possible)
3. The carbon atoms are numbered to give the double-bonded carbon atoms the lowest numbers.
2-ethyl-3-methyl-1-pentene
CH2 C CH CH3
CH2
CH3
CH2
CH3
One change: the name now ends in –yne
Practice:
CH3 C C CH3CH2 CH2 C C H
Cl
Carbon atoms are arranged to form rings
Named by prefixing cyclo- to the name
cyclopropane cyclobutane cyclopentene
Branches can also form off of cyclic compounds
To number the branches, use the lowest combination of numbers
If there is a double or triple bond in the ring, those atoms will be C1 and C2
Example Notice the double bond. So the chain is on C3
(lowest possible)
3-ethylcyclopentene
CH
CH
CH2 CH2
CH CH2 CH3
Practice CH
CH
CCH2
CH2
CH2
CH3
CH3
For convenience, rings are often simply represented as geometric figures
It is understood that there is a carbon (with the appropriate number of hydrogen) at each point
cyclobutane cyclopentene 1,2,3-tricyclohexane
The general formula describes the number of C atoms to the number of H atoms
Alkanes: CnH2n+2
Alkenes and Cycloalkanes: CnH2n
Alkynes: CnH2n-2
Helps easily find the formula for a
hydrocarbon
Naming and Drawing Alkenes and Alkynes
Worksheet #3
Cyclic Compounds
Worksheet #4