http://moodle.rockyview.ab.ca/mod/book/pr
int.php?id=58486

I.
Alkanes are very unreactive due to single C C
bonds. All combustion reactions are highly
exothermic.(low polarity &van der waals)
Complete Combustion:
2C8 H18 + 25O2 => 16CO2 + 18 H2 O
II. Incomplete Combustion
C8 H18 + 9O2 => 2CO2 + 9 H2 O + C + 5CO
C and CO are emitted as particulates. Read
page 193
Solve Hodder page 300, question 10.

Question 9
Homolytic Fission:
When the cleavage of covalent bond between two atoms
takes place in a manner, which enables each atom to
retain one electron of the shared pair.
This fission is symmetrical and leads to the formation of atoms or groups
of atoms having unpaired electrons, called free radicals.
Cl-Cl
=>
Cl●
+
chlorine
free radical
( Cl atom )
Cl●

Heterolytic fission is unsymmetrical , one of the
fragments takes both the electrons of the shared
pair, leaving none on the other. This results into
two charged particles as:
C6 H5CH2
Cl =>
C6 H5CH2+
+ Cl-
ALKANES UNDERGO SUBSTITUTION
ALKENES UNDERGO ADDITION

Alkanes undergo free radical substitution. This reaction
takes place in a series of steps. With excess of the
halogen, it continues until all the hydrogens were
substituted)
CH4 (g) + Cl2 (g) => CH3 Cl(g) + HCl(g)
(1)
Initiation Step:
(2) Propagation Step:
(3) Termination Step:
With excess of the halogen, it continues until all the
hydrogens were substituted)
Solve Hodder page 300, question #8 and 11
1. The active species in the chlorination of an alkane is
A.
Cl2 molecules
B. Cl atoms
C. Cl– ions
D. Cl+ ions
2. This question concerns several different compounds with two carbon atoms.
Ethane, C2H6 , reacts with chlorine to produce chloroethane as the first product.
(i) Write a balanced equation for this reaction.
(ii) This reaction will not occur simply by mixing the chemicals. What else is required?
(iii)What mechanism is involved in this reaction?

ALKANES UNDERGO FREE RADICAL
SUBSTITUTION.

ALKENES AND ALKYNES UNDERGO
ADDITION !!

The main source of alkenes is from the
cracking of the higher fractions.
C10H22 (g) => C8H18 (g) + C2H4(g)
About 10% of the crude oil is converted into
alkenes.
They are used as a chemical feedstock:
plastics, solvents,detergents.

You may have heard
of biofuels being
used to fuel
automobiles. Biofuel,
or gasohol as it is
called in many
countries, is a
mixture of gasoline
and ethanol.

Margarines

PVC


There are three key areas for the use of
alkenes:
Hydrogenation of unsaturated lipids to make
margarine, the production of ethanol and the
production of polymers.

Alkenes undergo addition due to the
presence of the double bond.
Catalyst: Ni , 180◦C

Unsaturated fatty acids may be converted to
saturated fatty acids by the relatively simple
hydrogenation reaction.
Addition of hydrogen to an alkene
(unsaturated) results in an alkane (saturated).
H2C=CH2 + H2 ---> CH3CH3

Vegetable oils are commonly referred to as "polyunsaturated".
This simply means that there are several double bonds
present. Vegetable oils may be converted from liquids to
solids by the hydrogenation reaction. Margarines and
shortenings are "hardened" in this way to make them solid or
semi-solids.

It has long been recognized that saturated
fats tend to increase the blood level of the
"bad" LDL cholesterol.
Monounsaturated (one double bond) and
polyunsaturated fats (two or more double
bonds) found primarily in vegetable oils tend
to lower "bad" LDL cholesterol. An elevated
LDL-C increases the risk of developing
coronary heart disease.


Test for unsaturation: Bromine water is a yellow/orange
solution. The color will disappear because the product is
colorless: alkenes with Br2 (aq)
The hydrogen will tend to migrate to the side with the
greater number of hydrogen atoms.
This preference is known as Markovnikoff´s Rule.
DO THE REACTION WITH But 2 ene and HBr !!!!


Water does not react directly with alkenes
under normal conditions, concentrated
sulfuric acid is required:(page 201)
Reaction:


Monomer: ethene
Polymer: Polyethene

http://www.chem.umn.edu/services/lectured
emo/info/Breathalyzer.html
Different types of Alcohols
Primary (1º)
H
Secondary (2º )
CH3
│
│
CH3─C─OH
│
│
H
CH3
CH3
│
CH3─C─OH
│
CH3─C─OH
H
1C
3C
attached
to C-OH
Tertiary (3º)
2C
attached
to C-OH
attached
to C-OH
Oxidation of 1° Alcohols
In the oxidation [O] of a primary alcohol 1, one H is
removed from the –OH group and another H from the C
bonded to the –OH.
primary alcohol
aldehyde
[O
]
OH
│
CH3─C─H
H2O
│
H
ethanol
(ethyl alcohol)
(acetaldehyde)
O
║
CH3─C─H
K2Cr2O
7
H2SO4
ethanal
+
Oxidation of 2° Alcohols
The oxidation of 2 alcohols is similar to 1°, except that a
ketone is formed.
secondary alcohol
OH
│
CH3─C─CH3
│
H
2-propanol
ketone
[O
]
║
CH3─C─CH3 + H2O
K2Cr2O
7
H2SO4
O
2-propanone
Oxidation of 3° Alcohols
Tertiary 3 alcohols do not oxidize.
Tertiary alcohol
no reaction
OH
│
CH3─C─CH3
[O
]
no product
│
CH3
no H on the C-OH to oxidize
K2Cr2O
7
H2SO4
2-methyl-2-propanol

If we compare the physical properties of
ethanol, ethanal and ethanoic acid we can
devise a way of obtaining a good yield of
ethanal before further oxidation to ethanoic
acid.
Ethaol and ethanoic acid: hydrogen bonds
Ethanal: dipole dipole , lower BP

Distillation apparatus


ethanol
H+ /Cr2 O7-2


The scheme below can be used to devise reaction
pathways. They should involve no more than two
steps.
Converting 2 butene to butanone:







http://www.chem.umn.edu/services/lecturedemo/info/Breathalyzer.html
1.
A.
B.
C.
D.
Which alcohol undergoes oxidation most easily?
CH3CH2CH2CH2CH2OH
CH3CH(OH)CH2CH2CH3
CH3CH2CH(OH)CH2CH3
(CH3)2C(OH)CH2CH3
A small amount of alkanol, RCH2OH, is added to a warm solution of potassium dichromate(VI) and sulphuric acid and left for
some time. When the reaction is complete, which functional group will be present in the product?

A.

RCH2––O––CH2R


O


B.
RC––H


O


C.
RC––O––H


OO


D.
RC––O––CH2R