TITLE- E1 AND E2 MECHANISM,CHEMICAL
COMPOSITION AND PROPERTIES OF PETROLEUM.
Abstract.
This document presents the research about E1 and E2 mechanism,
chemical compositions and properties of petroleum, it begins with E1
and E2 mechanism where it discuses mainly kinetics, order of reactivity
of alkyl halides and comparison between E1 and E2 reactions,
Ozonolysis, of alkenes, Markownikoff’s orientation. Finally, its details
the chemical composition and properties of petroleum, which is mainly
made of various number hydrocarbons such as carbon and hydrogen,
some of which also contain heteroatoms mostly sulfur, oxygen and
nitrogen. They main hydrocarbon types explained in this paper include
paraffin’s, naphthenes (cycloparaffins), aromatics, and hydrocarbons
series and the chemical configuration and physical properties of
petroleum. However, we collected the data and study it as methodology
to perform the research.
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TABLE OF CONTENS.
I. INTRODUCTION…………………………………………………………………..3
II. LITERATURE REVIEW…………………………………………………………..4
III. CHARACTERISTICS OF E1 AND E2 MECHANISM……………………….5
A. E1 MECHANISM………………………………………………………..…………….6
B. E2 MECHANISM…………………………………………………………….……….7
C. OZONOLOSISY…………………………………………………………….…………8
D. MARKOWIKOFF’S RULE…………………………
iv.
CHEMICAL COMPOSITION AND PROPETIES OF
PETROLEUM………………………………………………………………….10
A. CHEMICAL COMPOSITION OF TYPICAL
PETROLEUM…………………………………………………………………………..11
B. PHYSICAL PROPERTIES OF
PETROLEUM………………………………………………………………………….12
C. HYDROCARBON
SERIES……………………………………………………………………….…………12
v.
RESEARCH
GOALS……………………………………………………………….………..13
vi.
RESULTS AND
DISCUSION……………………………………..………………..…...…….14
vii.
CONCLUSION……………………………………………………..………..14
viii.
REFERENCES…………………………………………………....…………15
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I. Introduction
The elimination reaction in a different types of organic reaction in
which two substituent’s are removed from a molecule in one or two step
mechanism where it describe the reaction that goes by second-order
kinetics, Hughes and ingold is referred as E2 mechanism of reaction and
it is one-step mechanism and the two-step mechanism is known as E1
reaction. The comparative differences between E2 bimolecular and the
goes in second order while E1 is unimolecular first order. The
composition of petroleum is a complex mixture that constitute primarily
of hydrocarbons, derived from ancient living organisms deposited as
geological sediments.
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LITERATURE REVIEW.
Elimination reaction is a type of organic reaction in which two
substituents are removed from a molecule in either a one or two- step
mechanism. The one –step mechanism is known as the E2 reaction and
the two-step mechanism is known as the E1 reaction. In most organic
elimination reactions, at least one hydrogen is lost to form the double
bound. The unsaturation of the molecule increases. It is also possible
that a molecule undergoes reductive elimination, by which the valence
of an atom in the molecule decreases by two, though this is more
common in inorganic chemistry. There are three importance events in
these elimination reactions:
i.
Removal of a proton
ii.
Formation of the CC  bond.
iii.
Breaking of the bond to the leaving
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II. CHARACTERISTIC OF E1 AND E2 MECHANISM
Characteristics of E1
Characteristics of E2
reaction
Unimolecular reaction
Biomolecular reaction
Two step reaction
Single step reaction.
Carbocation intermediate formed. Hydrogen removes from beta
carbon.
Reactivity order of RX is
Trans elimination because low
321
energy consumption
No stereospecfic
Anti periplanar attack
Follow ziatsev rule.
Polar aprotic solvent best.
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Polar protic solvent good because
Phenyl group influences
stabilized ionic intermediate
elimination because product
alkenes further stabilized by
resonance.
Rate of reaction increases when
Reactivity order 321. No
concentration of substrate
steric effect.
increases
Rearrangement may take place.
Strong nucleophile influence
elimination.
No intermediate formed.
Examples.
6
e
A. E1 MECHANISM.
• E1 indicates an elimination, Unimolecular reaction, where
rate = KR-L-G. ( R-LG = Substrate)





H⎯C⎯C⎯LG→ H⎯C⎯C LG




Loss of the leaving group, LG, to generate a carbocation intermediate
then.



B H⎯C⎯C+  B⎯H




C=C


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Loss of proton H +, from the carbocation to form the -bond
Reaction influence the reaction pathway:
E1 mechanistic pathway is most common with:
Good leaving groups
Stable carbocation
Weak bases.
E1 reaction is non-stereo specific-follows zaitsev rule
Does not occur with primary alkyl halides (leaving groups).
E1 mechanism for Alcohols.


H+ 
H⎯C⎯C⎯OH 


C= C



E1 Mechanism for Alkyl Halides.
−


B
 
H⎯C⎯C⎯X  C=C


 
X= I, Br, C1, (F)
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B. E2 MECHANISM.
E2 Mechanism indicates an elimination, biomolecular reaction where
rate = K (B) [R-LG].This implies that the rate-determining step involves
an interaction between these two species, the base B, and the organic
substrate, R-LG.
• Kinetics---- second order
• Mechanism-single step.
• Stereospecfic
• Concerted-all bonds form form and break at same time
• Favoure by stronge base.
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C. OZONOLYSIS
Ozonolysis is an organic reaction where the unsaturated
bonds of alkenes, alkynes, or azon compounds are cleaved
with ozone.
D. MARKOWIKOFF; S RULE:
The rule state that with addiction of a protic acid HX to
asymmetric alkenes, the acid hydrogen (H) becomes
attached to the carbon with more hydrogen subsituents,
and the halide (X) group becomes attached to carbon with
more alkyl subsituents.
III. CHEMICAL COMPOSITION AND PROPERTIES OF
PETROLEUM.Composition by weight element percent range as
follow, carbon 83 to 85%, hydrogen 10 to 14% nitrogen 0.1 to 2%
Oxygen 0.05 to 1.5% sulfur 0.05 to 6.0% metals0.1%
Hydrocarbon average range Alkenes (paraffins) 30% 15 to
60% Napthenes 49% 30 to 60% Aromatics 15, 3 to30%
Asphaltic 6% remainder. Lighter hydrocarbons methane,
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ethane, propane and butane occur as gases pentane and
heavier ones are in the form of liquids or solids.
A. Hydrocarbon series.
A saturated hydrocarbon (some time called alkane) is one
which the valence of all the carbon atoms is satisfied by
single bonds for each carbon atom is connected to each
other carbon atom by a single covelant bond e.g. parrafins.
An saturated hydrocarbon is one in which the valence of
some of the carbon atom is not satisfied by single bond, so
that these atoms are connected to one another with two or
more covalent bonds e.g. benzene.
Paraffin
Parafins are also known as Alkanes and have the general
formula of CnH2n+2 where n is the number of carbon
atoms. Paraffins from C1 to C40 usually appear in crude oil
and represent up to 20% crude by volume. They are stable
and remain unchanged overlong periods of geological time.
Naphthenes.Napthenes or cycloparaffins are ring or
cyclic saturated hydrocarbons with the general formula
CnH2n. thermodynamic studies show that napthene rings
with five and six carbon atoms are the most stable
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naphthenic hydrocarbons. The content of cycloparaffins in
petroleum may vary up to 60%.
Aromatics.
Aromatics are an importance series of hydrocarbons found
in most every petroleum mixture from any part of the
world. This series of aromatics is called alkyl benzenes and
have a general formula of CnH2n-6 (where n6).
Asphaltenes
They are composed of fused benzene-ring network, but
they contain impurity atoms and are not true hydrocarbons.
These impurities are the high in molecular weight
compound previously referred to as NSO compounds.
Asphaltenes are heavy compound of crude oil and the major
components in many natural tars and asphalts.
B.
CHEMICAL PROPERTIES OF PETROLEUM.
Hydrocarbons are found in nature in many different forms,
mainly as: Liquid petroleum: known as crude oil to
distinguish it from refined oil it is most important
commercially.
Natural gas: which is lighter fraction of hydrocarbons, can
be free or dissolved.
Asphalt, tar, and pitch:
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C. CHEMICAL COMPOSITION OF TYPICAL
PETROLEUM.
ELEMENT
NATURAL GAS
CRUDE OIL
ASPHALT
CARBON
65-80
82-87
80-85
HYDROGEN
1-25
12-15
9-11
SULPURE
0.2
0.1-6
2-8
NITROGEN
1-15
0.1-2
0-2
OXYGEN
0
0.1-5
0
D. Physical properties of petroleum.
The physical properties are most commonly used in
petroleum are as follows. Specific gravity, volume, viscosity,
refraction index, fluorescence, optical activity, color, odor,
boiling point.
IV. Research goals.
To understand E1 AND E2 reactions and how the differ significantly in
the nature of transition states that determine the regiochemistry of the
product, the pathway involves a transition state leading from starting
material directly to the product,to understand two main methods
involved in the reaction that is dehydration (elimination of water) and
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dehydrohalogenation (Removal of a hydrogen atom and a halogen
atom).
To know the petroleum properties and how they are use in to check
quality of fuel oil, to differentiate between difference of petroleum using
chemical or physical properties.
V. Result and discussion
Because there are two mechanisms for nucleophilic substitution, there
are also two elimination mechanisms. The E1 mechanism is nearly
identical to the Sn1 mechanism, differing only in the course of reaction.
The alkanes from Pentane (C5H12) to Octane (C8H18) are refined into
petrol and the one from nonane (C9H20) to hexadecane (C16 H34) are
refined into diesel fuel, kerosene and jetfoil. Alkanes with more than 16
carbon atoms can be refined into fuel oil and lubricating oil. Paraffins
wax is an alkanes with approximately 25 carbon atoms. Asphalt has 35
and up carbon atoms. Those with four or fewer carbon atoms are in
gaseous state at room temperature.
VI. Conclusion.
The usual mechanism for dehydrohalogenation is E2 mechanism.
Its exhibits second-order kinetics, and both the alkyl halide and
the base appear in the rate equation. The reaction is concertedbonds are broken and form single step. Regarding chemical
composition and properties of petroleum, the hydrocarbon
structures found in oil include saturates, aromatics, and polar
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compounds that include resins and asphasltenes. The resins and
asphaltenes are largely recalcitrant in the environment.
VII. REFERENCES.
Robert J. Ouellette, j. David rawn, in organic chemistry, Haloalkanes and
alcohols nucleophilic substitution and elimination reaction, second
edition, 2018.
Chemicals composition of petroleum journal, by chang Samuel Hsu, Paul
R Robinsin. https://www.link.spriger.com
https://www.sciencediret.com, origin, composition and properties of
petroleum.
https://www.slideshare.net physical and chemical properties of
petroleum Oct 8, 2016.
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