Naming Unsaturated Hydrocarbons
Unsaturated:
Hydrocarbons with one double bond are called
_________________. All of their names end in _________.
Hydrocarbons with one triple bond are called ________________.
All of their names end in _________.
A prefix is still used to denote _____________________________.
One more thing is added to the names of unsaturated
hydrocarbons: a ______________ to say which carbon the double
or triple bond is attached to.
For example, 2-heptyne looks like this:
Remember that every carbon always has ______ bonds.
Use the molecule kits to build the following molecules and fill in the chart. Assess the molecular
formulas to determine the relationship between the number of carbons and the number of hydrogens
for molecules with a double or triple bond.
Name
2-butene
3-pentene
1-propyne
1-butyne
1-ethene
2-pentyne
Structural Diagram
Formula
Writing Formulas For Unsaturated Hydrocarbons
For alkenes the number of hydrogens is always ___________________ the number of carbons.
The general formula can be written as:
where n is the number of carbons.
For alkynes the number of hydrogens is always ___________________ the number of carbons plus _____.
The general formula can be written as:
where n is the number of carbons.
Write the formulas for the following hydrocarbons:
1. 2-hexene = _____________
2. 1-ethyne = _____________
Drawing Unsaturated Hydrocarbons
1. Determine the number of carbons and draw
Example: 3-Heptene
that many in a row connected by a single line.
2. If the molecule name ends in –ene you know
that there is a double bond. If the name of the
molecule ends in –yne you know that there is a triple bond. The name of the molecule will tell you
where that bond is located. For example, 2-butene will tell you that there are 4 carbons and the double
bond is located after the second one. Add another line for the double bond or two lines for a triple
bond.
3. Each carbon atom must have 4 bonds connected to it. Add enough hydrogens so that each carbon has
4 total bonds connected to it.
4. Use the molecular formula to make sure that you have the correct number of hydrogens.
3-Heptene =