Paper Hydrocarnon and its and Derrivatives GROUP 1

STRUCTURE THEORY OF STRUCTURE, LEWIS AND LINUS PAULING FOR H2O, CH4,
ETHENA, ETHUNA AND FORMALDEHID MOLECULES
Lecturer: Dr. Marham Sitorus., M.Si

Arranged by :
 Akhirunnisa Audina (4201131018)
 Annisa Rahayu (4203131045)
 Catherine Juperta H Marbun (4203331023)

BILINGUAL CHEMICAL EDUCATION STUDY PROGRAM
DEPARTMENT OF CHEMISTRY

MEDAN STATE OF UNIVERSITY 2020/2021

FOREWORD
Praise the presence of Allah SWT for giving His grace and guidance so that we can
complete the paper entitled "The theory of the structure of Kekulé, Lewis and Linus Paulng for
the molecules of H2O, CH4, Ethene, Ethane and Formaldehyde" on time.
The purpose of the writing of this paper is to fulfill the duties onhydrocarbon courses. In
addition, this paper also aims to add insight into "Kekule, Lewis and Linus Paulng's structural
theory for H2O, CH4, Ethene, Ethene and Formaldehyde molecules" for readers as well as for
authors.
We thank you Mr. Dr.Marham Sitorus., M.Si , who has given this assignment so as to
increase knowledge and insight in accordance with the field of study we are engaged in.
We also thank all those who have shared some of their knowledge so that we can
complete this paper.
We realize that the paper we write is far from perfect. Therefore, we will wait for
constructive criticism and suggestions for the perfection of this paper.

Medan, 19 May 2021

GROUP 1

CHAPTER I
PRELIMINARY

A. Background

In everyday life we often take for granted the world around us, along with the changes
that occur in it, asking for example, what is water? what is gasoline? why can gasoline burn and
water not? What is the meaning of tarbakar? Why does iron rust and gold not? What is rubber
and how to make artificial rubber? The questions above are some of the problems discussed in
chemistry. Therefore, chemistry can be defined as chemistry is the study of everything about
matter, such as substance, structure, properties, changes, and the energy that accompanies its
changes.

An atom combines with other atoms through chemical bonds so that it can form
compounds, both covalent and ionic compounds. Ionic compounds are formed through ionic
bonds, which are bonds that occur between positive ions (atoms that release electrons) and
negative ions (atoms that capture electrons). As a result, the compounds formed are polar. In
each compound, the atoms are joined together by a form of bonding between atoms which is
called a chemical bond. A chemist from the United States, namely Gilbert Newton Lewis (1875-
1946) and Albrecht Kosel from Germany (1853-1972) explained the concept of chemical bonds :

1. Rare gas elements (group VIIA) are difficult to form compounds because their electron
configuration has a stable electron arrangement.

2. A collection of data that is in an electronic format that is owned by rare gas elements, namely
by releasing electrons or capturing electrons.

3. If an element releases an electron, that is, an element of electrons in another element. In fact, if
you are not mistaken for an electron, it means accepting electrons from the elements. So a stable
arrangement when bonded to other atoms.

4. The tendency for atoms to have eight electrons in the outer shell is called the kaide octet.

B. Aim

This paper aims to make students able to explain Kekule Structure Theory, Lewis Structure and
Linus Pauling Structure H2O, CH4, Etuna and Formaldehyde.

C. Benefits

1. Knowing Kekule's structural theory
2. Knowing the Lewis structure theory
3. Knowing Linus Pauling's structural theory for H2O, CH4, Ethene, Etuna and Formaldehyde
molecules.

CHAPTER II
DISCUSSION

A. Kekule Structure Theory
Kekulé structure theory is the most khalasik theory based on the valence theory of

Frankland (1825-1899). Based on substance purification skills and both qualitative and
quantitative analysis, Frankland observes things like the table below:

Frankland argued that an atom is not only distinguished by weight but also by its
binding capacity which is called valence. The concept of valence at that time was defined as
the ability of an elemental atom to bind hydrogen atoms. Hydrogen atoms can bind an (H)
and form H2 molecules, so H has one valence. Furthermore, oxygen atoms can bind two H
atoms to form H2O molecules, then O has two valences and so on

Based on the combination of the theory of Frankland and Kekulé, several elements
have a valence and a notation like the one below,

Furthermore, according to kekule, when the valence lines join to form a bonding line,
a molecular model is obtained which is called the kekule structure as in the example below.

At first scientific experts laughed at this kekule structure. However, it turns out that
the kekule theory can explain that there are only two C2H6O molecules with a structure.

Science experts will be able to accept a hypothesis if a hypothesis (imagination) can
predict something that is proven by facts obtained from experiments (experiments). Until
now, organic experts could not make compounds with the molecular formula C2H6O in
more than two structures so that scientists could accept the kekule structure theory. The
above phenomenon is a type of isomer, hereinafter known as a functional isomer.

B. Lewis Structure Theory
The kekule structure theory views that each element is saturated, meaning that it can

no longer bind additional atoms. Thus ammonia (NH3) is saturated even though in fact there
are NH4 + molecules. At that time the concept of coordination had not yet been found

According to Bohr, the atom consists of a small, dense nucleus and electrons. The
electrons surround the nucleus while the nucleus consists of protons (positively charged and
neutrons (neutral), according to Bohr the maximum number of electrons in a shell (path) is
according to the formula: 2n2 (N = 1, 2, 3 ...), maximum electrons in each shell are 2, 8, 18,
etc. The arrangement of electrons in each shell is called the electron configuration with an
example of the electron configuration of several atoms as below:

Lewis and chemists argued that the electrons were responsible for the binding and
bonding forces depending on the energy of the electrons. By using the concept of valence
electrons, Lewis modified the notation to kekule with the grain concept, with some examples
of elemental atom notation as below:

According to Lewis's concept, the bonding between atoms in a molecule occurs due
to the sharing of electrons. The sharing of an electron pair occurs in order to fulfill the
octet method (which surrounds 8 electrons except hydrogern 2 electrons). Some molecules
with descriptions using Lewis structural theory are as follows:

Thus the concept of the (-) bond line in Kekulé theory is an electron pair (:) in Lewis
theory. Thus fundamentally there is no difference between the Kekule and Lewis
structures, because the bond lines in the Kekule structure have the same meaning as the
electron pairs in the Lewis structure.

C. Linus Pauling's Structural Theory
 Ethene
The phenomenon of the existence of single, double and triple bonds can be

explained both by kekule theory and Lewis theory, for example for a simple molecule
C2H4 (ethene) is described as follows:

In the kekule and Lewis structures the two bonds in the double bond are the same,
even though in fact the two bonds are different which is proven, that when an addition
reaction is carried out only one of them reacts and this is the basis of the Linus Pauling
structure theory.

linus pauling based his atomic theory on wave mechanics which put forward the
concept of orbitals. Orbital is the area most likely (most likely) to find electrons because
electrons have a dualism (de broglie) nature, namely electrons have wave properties
because they have very small masses (photons) the position of electrons in wave
mechanics is determined based on four quantum numbers

The principal quantum number (n) determines the energy level or size of the
orbital or in common language is determining the shell number (trajectory)
The azimuth (l) quantum number determines the shape of the s, p, d, or f orbitals
The magnetic quantum number (m) determines the direction and number of
orbitals
The spin quantum number (s) determines the maximum number of electrons in
an orbital which is 2 electrons with spin (+1/2) and (-1/2).
(1) The aufbau principle (charging electrons starts from the lowest energy)
(2) Hund rule (a stable configuration will form as many unpaired electrons as possible)
(3) Paul's exclusion (each orbital is occupied by a maximum of 2 electrons with the
following example:

The s orbital shape is a cylindrical sphere (no vertices), while the p and d
orbital forms are twisted balloons (having vertices). The number of s orbitals is
one while the number of p orbitals is 3 (px, py, and pz, the number of d orbitals is
5, while the number of f orbitals is 7 which is called degeneration orbitals (have
the same energy).

The bonding in the linus pauling structure uses the concept of
hybridization, which is the fusion (marriage) between atomic orbitals (OA) into a
molecular orbital (OM) which is based on the law of conservation of orbitals, i.e.
if n atomic orbitals combine it will produce n degenerate molecular orbitals.

Based on the concept of hybridization, molecular orbitals (OM) sp3, sp2 and sp
appear with molecular shapes and binding angles, respectively:

 Sp3 hybridation (tetrahedral, 109, 50)
 Sp2 hybridization (planar = flat, 1200)
 Hubridation sp2 (linear, 1800)
Atoms of the constituent elements of organic compounds that can undergo
hybridization as above are C, O and N.
Based on the linus pauling structure, it can be explained the difference between the
bonds between ó and π, while the ó bonds. In general, the ó bond is stronger than the π
bond, while the strongest ó bond is the hybrid (ss) bond in H2 and the weakest is the hybrid
(pp) on the halogen (X2). While the sequence of s and p hybrid strengths is: sp> sp2> sp3
due to a decrease in s character towards sp3. In fact, the lone pair is also a bond
symbolized by n (non-bonding electrons) which is weaker than ó and π. So if you do an
addition (addition) reaction to an alkene then what reacts (breaks) is the π bond.

 Methane (CH4)
The hybridization theory was promoted by chemist Linus Pauling in explaining the

structure of molecules such as methane (CH4). Historically, this concept was developed for
simple chemical systems, but this approach has been applied more widely, and is now
considered an effective heuristic for rationalizing the structure of organic compounds.

In CH4, the four sp3 hybrid orbitals overlap with the hydrogen 1s orbital, resulting
in four sigma bonds. These four bonds have the same length and bond strength, so that it is
in accordance with the observation.

An alternative view is to view carbon as a C4− anion. In this case, all of the
carbon orbitals are filled:

If we recombine these orbitals with 4 hydrogen s-orbitals (4 protons, H +) and
allow a maximum separation of 4 hydrogens (i.e. tetrahedals), then we can see that at
each orientation of the p orbitals, a single hydrogen will overlap. of 25% with the C-s-
orbital and 75% with the three C-p-orbitals. This HaL is equal to the relative percentages
between the s and p of the sp3 hybrid orbitals (25% s and 75% p).

According to orbital hybridization theory, the valence electrons of methane should have
the same energy level, but the photoelectron spectrum [3] shows that there are two bands,
one at 12.7 eV (one electron pair) and one at 23 eV (three electron pairs). . This
inconsistency can be explained if we consider the combination of additional orbitals that
occurs when the sp3 orbitals combine with the 4 hydrogen orbitals.
 Etuna

ethyne molecules; Atoms of each carbon atom σ-bonded with hydrogen, but triple
bond with the carbon itself. In ethyne, only the 2s orbital and one p orbital are hybridized
to produce two sp hybrid orbitals capable of forming two σ bonds per carbon atom in
ethane.

Ethene structure

Hybridization of carbon atom orbitals to form two sp hybrid orbitals
The two hybridized sp orbitals are arranged to form a linear geometry with a bond angle
of 180o.

The two unhybrid 2p orbitals in the two carbons form two triple bonds with two π
bonds. Other hybridations produced according to the valence bond theory include the
dsp3, d2sp3 hybrid orbitals.

CHAPTER III

CLOSING

A. Suggestion

From the above discussion it can be stated that :
* Lewis structures show each atom and its position in the structure of each molecule using its
chemical symbol. Lines are drawn between the atoms that are bonded to each other (pairs of dots
that can be used as a line). The excess electrons that make up the lone pair are represented as
pairs of dots, and are placed next to the atom. Although none of the major groups from the
second period onwards normally react by gaining, losing, or sharing electrons until they reach
the valence electron shell with a full octet (8) of electrons, no other rule obeys a different rule.
Hydrogen (H) can only form bonds that have only two electrons, whereas transition metals often
conform to the duodectet rule (12) (for example, compounds such as permanganate ions).

*Kekulé's Structural Theory states that carbon atoms are arranged in a hexagonal form where
there are double bonds alternating between carbon atoms, and there is a weakness, namely that
the double bond in benzene should have a tendency to react. Additional. In fact, a lot of benzene
is involved in substitution reactions. And different bonds are single bonds and double bonds. But
in reality, according to experiments, benzene has only one bond length of 0.139 nm. This shows
that all the bonds in benzene are the same.

*Linus Pauling's Structural Theory argues that electrons act as waves which take their positions
around atoms based on their wavelengths. Pauling also developed the Resonance Theory, a
concept which shows that in a given molecule, the electrons are held together by several atoms.

BIBLIOGRAPHY

Zumdahl, S S. 2009 Chemical Principles Sixth Edition. Houghton Mifflin Company, New York.
Fessenden, Ralph J. and Joan S. Fessenden. 1982. Organic Chemistry. Jakarta: erlangga
Risqiana, FA 2013. "Systematics of Hydrocarbons in Teaching Materials Textbook for High
School Students Studying the Sciences Chemistry" (Online)