Hydrocarbons are organic compounds made of only carbon and hydrogen. They include fuels, plastics, and other important products. The document describes tests conducted on various hydrocarbons to observe their physical and chemical properties. Acetylene was synthesized from calcium carbide and water, and reacted with bromine solution and potassium permanganate solution. Solubility, density, reactions with sulfuric acid, bromine, and potassium permanganate were tested for cyclohexane, cyclohexene, toluene, and chlorobenzene. The results showed that properties and reactivity differed based on whether the hydrocarbons were saturated, unsaturated, or aromatic compounds.

1. HYDRO C ARBONS

2. Hydrocarbons are organic compounds that contain
only carbon and hydrogen. They are extremely
important to our society because so many products are
derived from them:
fuels, fabrics, plastics, antifreezes, anaesthetics, insecticid
es, to name a few. The major source of aliphatic
hydrocarbons is petroleum, an extremely complex
mixture of compounds. Each of us, on the average, uses
several tons of petroleum each year (directly or
indirectly), mostly for fuel. Aromatic hydrocarbons are
mainly obtained from coal, although small amounts are
also obtained from petroleum.

3. Hydrocarbons may be saturated or unsaturated. A
saturated hydrocarbon is one that is maxed out in terms
of the number of hydrogen that can be present given
the number of carbons in the compound; it is impossible
to add more hydrogen atoms to the compound so it is
saturated with hydrogen. Acyclic alkanes are saturated;
there is no way additional hydrogen can be added
while keeping the same number of carbons and
maintaining normal bonding between the atoms.
Alkenes, alkynes, aromatic compounds, and cyclic
alkanes are unsaturated because hydrogen can be
added to them, in theory and usually in practice,
making them into acyclic alkanes.

4. Objective
 To observe physical and chemical
properties of some hydrocarbons
through tests

5. Outline of Procedure
A. Synthesis and Reaction of Acetylene
 in a two separate test tubes, measure 4 mL bromine
solution & 0.1% potassium permanganate
 place small pieces of calcium carbide in a dry test
tube fitted with a delivery tube, putting its end into
the bromine solution
 remove the cover of test tube and add water and
put it back immediately. Observe any changes in
color
 remove the delivery tube and bubble acetylene
through the potassium permanganate solution. Note
any changes in color

6. B. Solubility Tests
 mix 1 mL of each hydrocarbon to about 5 mL water
 note whether they are soluble, if not, note the
relative density of the hydrocarbon with respect to
water
 test the miscibility of two hydrocarbons (cyclohexene
& toluene) with each other by mixing 1 mL of each
C. Sulfuric Acid Tests
 add five drops of concentrated sulfuric acid to 1 mL of
each hydrocarbon, observe

7. B. Bromine Tests
 place 1 mL of each compound to be tested except
alkanes in a clean, dry test tube
 add drop by drop bromine solution (not more than
10 drops) to each compound. Observe
 do the same direction above, now in two test tubes
containing 1 mL alkanes
 expose one near a light bulb, let the other one remain
in the locker
 compare the time it takes for the sol’n to decolorize
C. Potassium Permanganate Tests
 add 2 drops of potassium permanganate to 1 mL
each of the hydrocarbons, observe

8. Results
Synthesis and reaction of acetylene
Reagent Observation
0.1% KMnO4
From dark red-brown to pale yellow
to an almost-clear solution
Bromine solution Violet to red-brownish

9. Other tests
Tests cyclohexane cyclohexene toluene chlorobenzene
Solubility
in water Immiscible Immiscible Immiscible Immiscible
density Less dense Less dense Less dense Denser
H2SO4
No observable
change
Brown
precipitate
formed
Immiscible, layer
formed
Immiscible, layer
formed
Bromine
without light
No observable
change, 5 mins
Colour of
bromine
disappears after
each drop
Color became
lighter; turbid
Slight change in
color
with light
Color changed;
became hazy,
3-5 mins
KMnO4 No change
Turbid organic
layer formed
Layer formed;
purple layer on
top
Layer formed,
purple layer at
the bottom

10. Discussion
Acetylene is formed when water reacts with calcium
carbide, CaC2.
Hydrocarbons are molecules that have little or no
polarity because they do not contain electronegative
atoms. They are soluble in solvents of low polarity. They
are not soluble in water, which is very polar, because the
water molecules attract each other strongly (and are not
nearly as interested in attracting nonpolar molecules).
That explains why hydrocarbons we have tested on the
experiment are all immiscible in water.
Mixing cyclohexane with conc. sulfuric acid shows no
observable change, that is because alkanes do not react
with conc. sulfuric acid. Unlike alkenes. Aromatic
hydrocarbon rings, such as toluene and
chlorobenzene, react quite slowly.

11. In bromine tests, bromine does not react with saturated
hydrocarbons (alkanes) because alkanes contain only C-C
bonds which cannot add bromine. Where in the
cycloalkanes solution, the color of the bromine solution was
only diluted to orange to light orange unless added with UV
light where it resulted in Bromine slowly disappearing over
time. Bromine readily reacts with unsaturated hydrocarbons
due to the C=C bonds that can be broken through addition
reaction. Where adding the bromine solution to
Cyclohexene will result in the disappearance of color of the
bromine solution after each drop and agitation. Aromatic
Hydrocarbons are unreactive with bromine without a
catalyst and may result in the dilution of the color of
bromine to orange to yellow.
In adding KMnO4 to cyclohexane, the KMnO4 was only
diluted indicated that it is unreactive to alkanes. In adding
KMnO4 to cyclohexene, it resulted in forming a purple
precipitate. Aromatic Hydrocarbons just like with alkanes
are unreactive to potassium permanganate.

12. Conclusion
Hydrocarbons can be known and be differentiated by their physical
properties and chemical reactivity. According to their solubility,
these hydrocarbons are insoluble; immiscible to water as they are
nonpolar substances as opposed to the high polarity of water. The
densities are the same for each with the exception chlorobenzene
due to the hydrogen bonds that have to be broken, the dispersion
forces that are acting upon the molecule as opposed to making
new bonds in reacting water with chlorobenzene. These
hydrocarbons also react with a conc. H2SO4 solution although
insoluble forming hydrogen bonds to the hydrocarbons. Even
Aromatic compounds also react with conc. Sulfuric acid as it
undergoes a substitution reaction. Alkanes are unreactive to
bromine unless under special condition or catalyst like being
exposed to UV light also alkanes are unreactive to potassium
permanganate. Alkenes are readily reactive to bromine since its
double bounds can be broken easily through addition reaction also
is relatively similar if alkenes are added with KMnO4. Aromatic
Compounds are unreactive because they are usually stable and can
only be reacted if given a catalyst.