Download Physical Properties of Hydrocarbons

Hydrocarbons
at Room Temperature
 Gas
 Methane
 Ethane
 Propane
 Butane
 Liquid
5 to 19
Carbons
 Waxy
20 to 40
Carbons
 Plastic
40 or more
Carbons
Melting Point
As the length of hydrocarbons get longer, the
Melting Point grows Higher.
Why?

Melting and Boiling Temperatures of Alkanes
600
500
Tempurature (˚C)
400
Boiling Point (˚C)
300
200
Melting Point(˚C)
100
0
-100
-200
-300
0
5
10
15
20
25
Number of Carbons
30
35
40
45
What other material properties
change?
 Viscosity
 Hardness
 Toughness
 Flammability
Physical Properties of Hydrocarbons
• The first four alkanes (C1 to C4) are all gases at room
temperature.
• Compounds from C5 to C17 are oily liquids.
• Compounds greater than C17 are solids at room
temperature and pressure.
• As the number of carbon atoms increases, the
molecules become larger and heavier. This also means
that their melting points and boiling points increase.
• Liquid alkanes are insoluble in water, are less dense
than water. Alkanes are soluble in non-polar solvents.
Reactions of hydrocarbons
• Complete Combustion (oxidation)
reactions
Alkanes, alkenes and alkynes burn in air
reacting with the oxygen in air to produce
carbon dioxide and water.
CH (g) + 2O (g) CO (g) + H O(g)
• Incomplete combustion (oxidation)
reactions produces carbon monoxide and
water vapour.
4
2
2
2
Reactions of alkanes
• Substitution reactions
Alkanes react with halogens in sunlight or at high temperature in a
substitution reaction.
Substitution continues if more halogens are present.
Su
UV light
S
• Alkanes
Reactions of the alkenes & alkynes
• When alkenes or alkynes react with halogens
they undergo addition reactions.
Naming hydrocarbons
Functional Groups
Functional groups
• Functional groups are parts of molecules
that result in characteristic features.
Name
Group
Naming
Halo alkanes
-X
The number of the carbon atom to which the halogen has
been bonded must be given followed by the halogen and
then the prefix indicating the number of carbons in the
chain.
Alkanols
-OH
Alkanols have the ending -ol.
Carboxylic
group
-COOH
add the ending -oic acid to the alkyl prefi x.
Ester
Amines
the alkanol (alkyl) name is given first, followed by
the acid part. The -oic
ending of the acid is replaced with -oate.
-NH2
the suffix -amine to the alkane group to which
the —NH2 has been added
Esters
• The carboxylic acids react with alkanols to
form esters. Esters are a group of compounds
which give the pleasant ‘fruity’ smell to
various fruits. This is called a dehydration or
esterification reaction.
Name and draw the expanded structural formula of the ester formed when
ethanol reacts with propanoic acid.
• .
Crude oil
• Crude oil, also called petroleum, is a complex
mixture of carbon and hydrogen (hydrocarbons),
which exist as a liquid in the earth's crust.
• The carbon and hydrogen in crude oil are thought
to have originated from the remains of
microscopic marine organisms that were
deposited at the bottom of seas and oceans and
was transformed at high temperature and
pressure into crude oil and natural gas.
Petroleum Refining
• Petroleum refining is the process of separating
the many compounds present in crude
petroleum. This process is called fractional
distillation where the crude oil is heated; the
various of the compounds boil at different
temperatures and change to gases; and are later
recondensed back into liquids.
• The principle which is used is that the longer the
carbon chain, the higher the temperature at
which the compounds will boil.
Fractional distillation
properties
The various components of crude oil have different sizes,
weights and boiling temperatures and viscocity
• bigger the molecule greater the intermolecular force
• ... more viscous as the intermolecular attractive forces
between molecules increases.
• ... higher melting point as more vibrational kinetic
energy is needed to overcome the intermolecular
attractive forces holding the molecules together to form
the crystals.
• ... less flammable as they become less volatile, again
due to increasing intermolecular forces.
Cracking
• Cracking is the name given to breaking up
large hydrocarbon molecules into smaller and
more useful bits. This is achieved by using high
pressures and temperatures without a
catalyst(thermal cracking), or lower
temperatures and pressures in the presence of
a catalyst(catalytic cracking).