3.1 Hydrocarbons: Types of Reactions
Define the following in your own words:
a) hydrocarbon
d) alkyne
b) alkane
e) structural isomer
c) alkene
f) geometric isomer
Physical Properties of Hydrocarbons
 non-polar
 large hydrocarbons are solids because they have
stronger intermolecular bonds, therefore a higher
melting & boiling point
o ex: coal, plastics
 smaller hydrocarbons are gases and liquids
o ex: methane (natural gas), propane, octane
(gasoline), etc.
propane (……………..) = low MP/BP
octane (……………..) = medium MP/BP
coal (……………..) = high MP/BP
Combustion Reactions of Hydrocarbons
 all hydrocarbons burn in the presence of oxygen to
produce large amounts of heat and light energy
o makes hydrocarbons useful fuels
 this reaction is an example of a combustion reaction
o ALK + O2  CO2 + H2O + 
 called “complete” combustion when lots of oxygen is
present and only carbon dioxide & water are
produced
o ex: complete combustion of propane
o
C3H8 + O2  CO2 + H2O + 
 your body’s cells undergo complete combustion every
moment of every day
o you take in O2 through your nose/mouth, your
cells split glucose, an organic compound, into
useful energy for muscle contraction, digestion,
normal body functions (homeostasis)
o the CO2 produced by your body’s cells travels
through your veins to your lungs where it’s
exhaled
o the H2O produced is perspiration
 when not enough oxygen is present, carbon
monoxide and carbon soot is produced instead
o called “incomplete” combustion
o ex: incomplete combustion of propane
o
C3H8 + O2  CO + H2O + C + 
 many other organic compounds like alcohols,
carbohydrates like sugars, etc., undergo combustion
as well
Ex: Write a balanced chemical equation for the
(complete) combustion of pentane.
Ex: Write a balanced chemical equation for the
(complete) combustion of 1-hexene.
HW: p. 188 Practice # 5
Addition Reactions of Alkenes and Alkynes
 alkenes and alkynes are more reactive than alkanes
because of their double/triple bonds
 double & triple bonds have substantially more energy
trapped inside them then single bonds
 double & triple bonds can be converted to single
bonds by performing chemical reactions
o energy is released during this process
 when the double/triple bond is broken, it allows other
atoms to combine with the carbon such as hydrogen,
halogens or “functional groups” like -OH (hydroxyl)
o called an addition reaction
o only occurs with alkenes or alkynes because
alkanes are already all single bonds
addition reaction = when a molecule (hydrogen,
halogen) is added to an alkene or
alkyne to break apart the
double/triple bond in a chemical
reaction
 ex: ethyne + hydrogen gas
What can be added to an ALKene/yne in an addition
reaction?
 hydrogen (H2) to saturate the carbons
o saturating tastes better
 foods are examples of natural organic
compounds
 halogens like Br2, Cl2, etc.
 acids like HCl, HBr, HI, etc.
 oxygen (forms alcohols, ketones, aldehydes, etc.)
 nitrogen (forms amines, amides, amino acids)
Ex: Use structural diagrams to represent an addition
reaction of hydrochloric acid to a propene molecule.
Ex: Use structural diagrams to represent an addition
reaction of water and 2-butene.
 when a double/triple bond is present, the molecule is
called unsaturated, but if it only has single bonds it is
a saturated molecule
o ex: saturated vs. unsaturated fats
 saturated fats are saturated with hydrogen
atoms
o fats are examples of complex organic molecules
polyunsaturated = hydrocarbon containing more than 1
double/triple bond
o healthier alternative to saturated fats
HW: p. 190 Practice # 6, 7
substitution reaction = when a halogen or hydrogen is
substituted for another in an ALK
o double/triple bonds aren’t broken but instead
hydrogens are replaced with halogens or vice versa
o ex: butane vs. 2-fluoro, 3-chloro butane
C4H10 vs.
C4H8FCl