Naming Alkenes, Alkynes, and Cyclics - Wikispaces - Naming Alkenes... · Contain less hydrogen than...

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