The chemistry of compounds
containing carbon.

Refinery and tank storage facilities, like this one in Texas, are
needed to change the hydrocarbons of crude oil to many
different petroleum products. The classes and properties of
hydrocarbons form one topic of study in organic chemistry.
A hydrocarbon is a compound
consisting of only hydrogen and
carbon.
 The carbon to carbon can be
single, double, or triple bonds.
 The bonds are always nonpolar.

an organic compound (as acetylene or butane) containing only carbon and
hydrogen and often occurring in petroleum, natural gas, coal, and bitumens
Here are some Characteristics of hydrocarbons:
Has non-polar molecules
sp3 hybridization
Contains only hydrogen and carbon
non-electrolytes because of poor ionization
In "most** situations, it is not soluble in water
The reactivity is very slow
The low boiling point makes it pretty easy to decompose
Presented by Brent Daigle, Ph.D. (ABD)

Carbon-to-carbon
bonds can be single
(A), double (B), or
triple (C). Note that in
each example, each
carbon atom has four
dashes,
which
represent four bonding
pairs of electrons,
satisfying the octet
rule.

Carbon-to-carbon chains can
be (A) straight, (B) branched,
or (C) in a closed ring. (Some
carbon bonds are drawn longer,
but are actually the same
length.)
1.
Hydrocarbons - molecules that possess only hydrogen and carbon
a1. Alkanes – noncyclic hydrocarbons with only C-C single bonds.
Formula CnH2n+2 where n is an integer.
Example:
Butane CH3CH2CH2CH3
C4H10
a2. Cycloalkanes – cyclic hydrocarbons with only C-C single bonds.
Formula CnH2n where n is an integer.
Example:
Cyclobutane
C4H8
b1. Alkenes – noncyclic hydrocarbons with C=C double bonds.
Formula CnH2n where n is an integer.
Example:
2-Butene CH3CH=CHCH3
C4H8
3-8
b2. Cycloalkenes – cyclic hydrocarbons with C=C double bonds.
Formula CnH2n-2 where n is an integer.
Example:
Cyclobutene
C4H6
c. Alkynes – noncyclic hydrocarbons with C≡C triple bonds.
Formula CnH2n-2 where n is an integer.
Example:
CH3C ≡ CCH3
Butyne
C4H6
d. Aromatic Hydrocarbons – benzene and its derivatives
H
H C C C H
C
H
C
C
or
C6H6
H
H
3-9
2. Compounds containing Oxygen
a. Alcohols R-OH
Functional Group OH hydroxyl group
CH3OH methyl alcohol
HOCH2CH2OH ethylene glycol (antifreeze)
b. Ethers
R-O-R
CH3CH2-O-CH2CH3 Diethylether
c. Aldehydes and Ketones
O
O
R-C-H
R-C-R'
Functional Group C=O carbonyl group
O
O
H
3-10
O
d.
O
Carboxylic Acids
R-C-OH
O
Functional Group
-CO2H
-COOH
-COH Carboxyl Group
O
O
CH3-C-OH
+
H3O+
H2O
+
CH3CO-
Acetic Acid
e. Derivatives of Carboxylic Acids
O
R-C-OR'
Ester
O
R-C-Cl
Acid Chloride
O
R-C-NH2
Amide
3-11
3. Nitrogen-Containing Molecules
a. Amines
R-NH2
Functional Group -NH2 amino group
CH3NH2
N
N
H
Amines are Lewis and Bronsted bases because of the nonbonded pair of electrons
..NH2
+
HCl
NH3+ Cl
b. Amides (see above)
c. Nitriles
R C N
Functional Group
C N
Cyano Group
3-12
Single versus Double Bonds
H
H
H
H
H
H
C
C
H
H
C
H
H
H
C
H
Ethane
The carbon-carbon single bond in ethane freely rotates at room temperature.
H
H
C
H
C
C
H
H
Ethylene
H
H
C
H
Pi bond broken
The carbon-carbon double bond in ethylene does not freely rotate at room temperature.
Why not?
Answer: The Pi bond would have to be broken. It will not break at room3-13
temperature
Isomers – different compounds with the same formula
a.
Constitutional (Structural) Isomers – isomers that differ in their bonding
sequence
CH3
CH3CHCH2CH3\
C5H12
CH3CH2CH2CH2CH3
C5H12
Br
Cl
vs
H
Br
H
C=C
C=C
H
H
C2H2BrCl
Cl
C2H2BrCl
b. Stereoisomers – isomers that differ in their spatial orientation
Br
Cl
C=C
H
H
Cl
C=C
H
C2H2BrCl
Cis isomer
H
Br
C2H2BrCl
Trans isomer
3-14
Use of Wedges and Dashed Lines
H
H C
H
H
Solid Wedge indicates “coming toward you”
Dashed Line indicates “going away”
Narrow Line indicates “in the plane of paper”
CH3
CH3
CH3
CH3
Question: Are the above cycloalkanes constitutional or stereoisomers?
Answer: Stereoisomers
3-15

•
•
•
•
Alkanes are hydrocarbons with only single bonds.
SATURATED HYDROCARBONS – they contain only
C&H
they have only C-C and C-H single bonds
Contain the maximum possible number of H per C
Occasionally
referred
to
as
ALIPHATIC
compounds; Greek aleiphas, meaning fat (many
animal fat contain long carbon chains similar to
alkanes)
 Alkanes occur in what is called a homologous
series.
 Each successive compound differs from the one
before it only by a CH2
Characteristics
AKA Paraffins, are chemical compounds that
consist only of the elements carbon (C) and
hydrogen (H). Each are linked by a single bond.
Each carbon atom must have 4 bonds (either C-H
or C-C bonds), and each hydrogen atom must be
joined to a carbon atom (H-C bonds).
General formula CnH2n+2 (Linear saturated
hydrocarbon)
Brent Daigle, Ph.D. (ABD)
Chemical structure of methane
the simplest alkane

1.
2.
3.
4.
5.
Tetrahedral
109.5o
MW=16 g/ml
PHYSICAL PROPERTIES
Non-polar – comparable
SOURCES:
EN of C & H;
1. END PRODUCT OF ANAEROBIC
symmetrical cmpd.
DECAY OF PLANT AND ANIMALS
 It is a major constituent of natural
Low b.p. (-161.5o), or
gas (97%)
o
low m.p.(-83 ) – weak
 Fire damp of coal mines
 Marsh gas bubbling in swamp
VW attraction.
 Methane can be isolated by
Colorless
fractional distillation
Sp. Gravity = 0.4 g/mL 2. OXIDATION BY HALOGENS
(HALOGENATION)
Slightly soluble in water
The Alkanes
Methane
H
H
C
H
CH4
H
Ethane
H
H
Propane
H
H
H
H
C
C
C
H
H H
H
Presented by Brent Daigle, Ph.D. (ABD)
H
C
C
H
H
C3H8
H
C2H6
The number of carbon atoms = root name!
meth
 eth
 prop
 but
 pent
 hex
 hept
 oct
 non
 dec

1 carbon
2 carbon
3 carbon
4 carbon
5 carbon
6 carbon
7 carbon
8 carbon
9 carbon
10 carbon
Presented by Brent Daigle, Ph.D. (ABD)
Physical Properties of Alkanes
1. Combustion - Alkanes are flammable, i.e. they burn.
CH4
+
2 O2
CO2
+2 H2O
2. Boiling and melting points
a. Both bp and mp increase with increasing carbon number for straightchain
alkanes with formula CnH2n+2
Carbon Number
C1- C4
C5 – C16
C17 – C30
C30 – C50
>C50
Physical State
gases
liquids
oils and greases
paraffin waxes
plastics (polyethylene)
3-21
b. Branching tends to lower the boiling point and raise the melting point
BP
60oC
58oC
50oC
MP -154oC
-135oC
-98oC
Explanation:
MP Branching reduces the flexibility of the molecule which
reduces the entropy term
S in the equation Tmp = H/S. Since S is in the denominator,
Tmp increases.
BP Branching reduces surface area (more compact structure), and
therefore London dispersion forces which control boiling point for
these molecules.
3. Solubility – alkanes are nonpolar molecules and therefore insoluble in water,
which is polar. Alkanes are hydrophobic.
4. Densities – alkanes are less dense than water, with densities near 0.7 g/mL.
Therefore they float on water, e.g. Exxon Valdez
3-22 oil spill.

Petroleum is a mixture of alkanes,
cycloalkanes, and aromatic hydrocarbons.


Petroleum is formed from the slow
decomposition of buried marine life, primarily
plankton and algae.
As petroleum is formed it is forced through
porous rock until it reaches an impervious
layer of rock.

Here it forms an accumulation of petroleum
and saturated the porous rock creating an oil
field.

Crude oil is the petroleum that is
pumped directly from the ground.
It is a complex mixture of
hydrocarbons with one or two carbon
atoms up to a limit of about 50
carbon atoms.
 This is usually not useful, so it must
separated by distillation.


Crude oil from the ground is separated into usable
groups of hydrocarbons at this Louisiana refinery. Each
petroleum product has a boiling point range, or "cut," of
distilled vapors that collect in condensing towers.

Petroleum
products and
the ranges of
hydrocarbons
in each
product.

The octane rating
scale
is
a
description
of
how
rapidly
gasoline burns. It
is based on (A) nheptane, with an
assigned octane
number of 0, and
(B)
2,2,4trimethylpentane
,
with
an
assigned number
of 100.
Octane Number
Straight-chain hydrocarbons have low octane and make poor fuels.
Octane Number = 0
heptane
Branched Alkanes burn more slowly and reduce the knocking in the engine.
Octane Number = 100
2,2,4-trimethylpentane
3-28
1. The first step in petroleum refining is fractional distillation.
3-29
Separate fractions
based on differences
in boiling point.
Refining of Petroleum
3-31
2. Upstream processing of the distillates.
a. Catalytic hydrocracking – produces small alkanes from large alkanes by
adding hydrogen.
H2, heat
Si-Al catalyst
b. Catalytic cracking – produces small alkenes and alkanes by cracking in the
absence of hydrogen.
heat
Si-Al catalyst
c. Catalytic Reforming – the alkanes and cycloalkanes are upgraded to higher
octane number by conversion into aromatic compounds.
-H2
catalyst, heat
-3H2
catalyst, heat
3-32



Removing
HYDROGEN
from an alkane, the partial
structure that remains is
called an ALKYL GROUP.
Are NOT stable compounds
themselves,
they
are
simply PARTS of larger
compounds.
Are named by replacing
the –ane ending of the
parent alkane with a –yl
ending.


In naming alkyl groups: the prefixes sec- (for
secondary) and tert- (for tertiary) used for the
C4 alkyl groups, refers to the number of other
carbon atoms attached to the branching carbon
atom.
There are 4 possibilities: primary
(1o),
secondary (2o), tertiary (3o) and quaternary
(4o).
Sample problems