Aim 2: Hydrocarbons
HYDROCARBONS
Hydrocarbons are compounds made up of atoms from only two
elements: Hydrogen and Carbon
IUPAC names identify the number of carbons in the longest
chain with a prefix:
number of
carbons
1
prefix examples
meth-
2
eth-
3
prop-
4
but-
5
pent-
6
hex-
7
hept-
8
oct-
9
non-
10
dec-
methane
ethane, ethene, ethyne
propane, propene, propyne
Every carbon atom must have 4 bonds (8 e- total)!
Every covalent bond has 2 shared e-s.
Every hydrogen atom must have 1 bond (2 e-)!
homologous
alkanes
series
bonds between only
carbon atoms single
bonds
general
CnH2n+2
formula
Saturated (S) S
Unsaturated
(US)
alkenes
alkynes
one
double
bond
CnH2n
one triple
bond
US
US
CnH2n-2
n = a certain number of carbon atoms bonded together
1
Alkanes (Paraffin Family)
-all bonds connecting carbon atoms (C-C bonds) are
single bonds
-saturated hydrocarbons
-CnH2n+2
-used for fuels
-each member of the series differs from the one
before it by CH2 (1 carbon and 2 hydrogens)
-the name will begin with the prefix representing the
number of carbons
-the name will end in -ane.
-methane is the only alkane that does not connect to
another carbon by a single bond because there is only
one carbon!
Types of Formulas
Examples:
Molecular Formula- shows the #
OF ATOMS of EACH ELEMENT;
least info
C2H6
Structural Formula- diagram of
the molecular structure of
compound
Condensed Structural Formulaeach Carbon is written separately
followed by atoms bonded to it
CH3CH3
2
Every carbon atom must have 4 bonds (8 etotal)!
Every covalent bond has 2 shared e-s.
Every hydrogen atom must have 1 bond (2 e-)!
You must be able to:
-determine the molecular formula for
-name
-draw the structural formula for
-write the condensed structural formula for all
alkanes.
Drawing Structural Formulas for Alkanes
Use Table P and Table Q to determine the # of
Carbon and Hydrogen atoms
Remember that each Carbon MUST have FOUR Bonds!!
3
Example: Formulas for Methane
Molecular:
Structural:
Condensed:
Example: Formulas for Ethane
Molecular:
Structural:
Condensed:
4
Isomers
Isomers are compounds that have the same molecular
formula (same number of atoms of each element) but
different structural formulas (different structures,
different physical properties, different chemical
properties, different names)
-The more carbons there are, the more isomers
there will be.
Alkanes have isomers. The carbons could be arranged
in a straight chain (unbranched) or there could be
branches of carbons that stem off of the largest
chain.
C4H10
C5H12
5
Alkenes (Olefins)
-there will be one C=C (double) bond
-unsaturated hydrocarbons
-CnH2n
-each member of the series differs from the one before
it by CH2 (1 carbon and 2 hydrogens)
-the name will begin with the prefix representing the
number of carbons
-the name will end in -ene.
-there is no "methene". This series starts with ethene.
-alkenes with 4 or more carbons allow for the double bond to
be placed in different spots along the chain. These are
isomers (same molecular formula; different names,
structures, and properties).
The lowest number of the carbon in the chain that
touches the double bond is part of the name of the molecule
(1-hexene is an isomer of 2-hexene).
Every carbon atom must have 4 bonds (8 e- total)!
Every covalent bond has 2 shared e-s.
Every hydrogen atom must have 1 bond (2 e-)!
You must be able to:
-determine the molecular formula for
-name
-draw the structural formula for
-write the condensed structural formula for all alkenes.
6
Example: Formulas for Ethene
Molecular:
Structural:
Condensed:
Example: Formulas for Propene
Molecular:
Structural:
Condensed:
7
Alkynes
-there will be one C≡C (triple) bond
-unsaturated hydrocarbons
-CnH2n-2
-each member of the series differs from the one before
it by CH2 (1 carbon and 2 hydrogens)
-the name will begin with the prefix representing the
number of carbons
-the name will end in -yne.
-there is no "methyne". This series starts with ethyne.
-alkynes with 4 or more carbons allow for the
triple bond to be placed in different spots along
the chain. These are isomers (same molecular
formula; different names, structures, and
properties).
The lowest number of the carbon in the chain
that touches the triple bond is part of the name of
the molecule (1-hexyne is an isomer of 2-hexyne).
Every carbon atom must have 4 bonds (8 e- total)!
Every covalent bond has 2 shared e-s.
Every hydrogen atom must have 1 bond (2 e-)!
You must be able to:
-determine the molecular formula for
-name
-draw the structural formula for
-write the condensed structural formula for all alkynes.
8
Example: Formulas for Ethyne
Molecular:
Structural:
Condensed:
Example: Formulas for Propyne
Molecular:
Structural:
Condensed:
9