MINISTRY OF EDUCATION AND
SCIENCE OF THE REPUBLIC OF
KAZAKHSTAN
KAZAKH
NATIONAL WOMEN TEACHER
TRAINING UNIVERSITY
INSTITUTE OF NATURAL
SCIENCES
DEPARTMENT OF
CHEMISTRY
SIW
Topic: Isomerism and Isomerism
types
Reviewed by: Sarsenbaeva
Zamira Berkbayevna
Performed by: 2nd year student
of the specialty
"6B01507-Chemistry"
Berdimatova Umida
Almaty
2022
Plan:
-
Introduction
1.1. А.M.Butlerovts chemical,
structural theory
II. The main
part
2.1. Isomerism of organic
compounds
2.2. Types of
isomerism.
2.3. Structural
isomerism
2.4. Spatial
isomerism
III.
Conclusion
IV.
References
Introduction
Before the emergence of AM
Butlerov's theory of chemical structure, the existence of
substances with the same composition and molecular weight, but
different in the location of atoms, remained unknown. These
substances have different properties. The ability of carbon atoms
to form four covalent bonds with other carbon atoms opens up the
possibility of several compounds with the same elemental
composition. This phenomenon is called
isomerism.
Prior to the development of
the theory of chemical structure, only one substance of
C4H10 butane with a linear structure
of the carbon chain was known. AM Butlerov suggested that the
molecular formula is the same, but the sequence of carbon atoms in
the molecule can be a different substance. Thus, an isomer of
butane was obtained, which is called isobutane (with a branched
structure).
In September 1861, at a
conference of naturalists in Speyer (Germany), AM Butlerov spoke on
"The chemical structure of matter." In this report, he presented
the main ideas of the theory of construction. The essence of this
theory consists of the following basic
principles:
1. All atoms in a molecule are
connected in sequence according to their valences. The order of
addition of atoms in a molecule and the nature of the bonds between
them M. Butlerov called it chemical structure. It is determined
that there are one, two and three bonds between and that the chain
of carbon atoms is open and closed:
2. Properties of substances
are their qualitative, quantitative,not only in the atoms of the
6ipre molecule the order of communication with each other and
between them.
This principle of the theory
of construction is an organic, widespread phenomenon of isomerism
in chemistry.
3. By studying the properties
of a given substance, it is possible to determine the structure of
the molecule of the substance and to some extent express the
structure and properties of the formula
6ip.
4. Atoms and groups of atoms
entering the molecule interact with each other, including the
interaction of directly connected
atoms.
Butlerov's idea of the
interaction of these atoms was further developed by his student VV
Markovnikov.
2.1. Isomerism of organic
compounds
Organic compounds are chemical
compounds (except for carbon oxides, carbon dioxide and its salts)
that always contain a carbon atom as the main element. From ancient
times the people used natural dyes, cane sugar, various oils, etc.
could use. The number of organic compounds has exceeded 5 million
due to the chemical interaction of carbon atoms with atoms of many
other elements. They are characterized by the phenomenon of
isomerism, which studies organic chemistry, and various complex
changes.
Before the advent of the
theory of the chemical structure of A. M. Butlerov, the existence
of substances that have the same composition and the same molecular
weight, but differ in the arrangement of atoms, remained unknown.
These substances have different properties. The ability of carbon
atoms to form four covalent bonds, including those with other
carbon atoms, opens up the possibility of the existence of several
compounds of the same elemental composition. This phenomenon was
called isomerism.
Before the creation of the
theory of the chemical structure, only one substance of the
composition `C4H10` was known - butane, which has a linear
structure of the carbon chain. A. M. Butlerov suggested the
possibility of the existence of another substance with the same
molecular formula, but with a different sequence of carbon atoms in
the molecule. Thus, an isomer of butane was obtained, which was
called isobutane (has a branched
structure).
There are three isomers for
pentane:
The boiling points of butane
and pentane differ from each other, which serves as evidence that
the properties of the compounds depend on the structure of their
molecules.
2.2. Types of
isomerism.
Isomerism. Structural and
spatial formulas and models According to the theory of chemical
structure, each substance has a specific chemical structure.
However, several substances can correspond to the same molecular
formula. But their chemical structure and structural formula are
different. Isomers are substances with the same qualitative and
quantitative composition and molecular weight, but different
structure and, accordingly, different properties. The order in
which carbon atoms interact with each other or with atoms of other
elements is called the phenomenon of isomerism. Therefore, ethyl
alcohol and dimethyl ether were considered isomers. The phenomenon
of isomerism is very common in organic chemistry and is one of the
main reasons for the abundance of organic
matter.
Isomerism means that each
compound has the same molecular formula, but each compound contains
two or more substances with different structures. In these
substances, called isomers, all the elements are in the same
proportions, but each molecule has a different structure of
atoms.
The word isomer comes from the
Greek word isomers, which means "equal parts". Contrary to the
prediction, isomers may or may not have similar characteristics
depending on the functional groups in their
structure.
There are two main classes of
isomerism: constitutional (or structural) isomerism and
stereoisomerism (or spatial isomerism). Isomerism is found in both
organic substances (alcohols, ketones, etc.) and in inorganic
substances (coordination
compounds).
Sometimes they appear
spontaneously; In these cases, the isomers of the molecule are
stable and under normal conditions (25°C,1 atm), which was a very
important breakthrough in chemistry when it was
discovered.
2.3. Structural
isomerism
Structural isomers - compounds
of the same qualitative and quantitative composition, differing in
the order of binding of atoms, i.e. chemical structure.Therefore,
structural isomers have the same molecular formula but different
structural formulas.
Types of structural
isomerism
-
The isomerism of the carbon
skeleton is due to the different order of atoms that form the
skeleton of molecules..For example, structural isomers of the
composition C5H12:
-
Position
isomerism:
-
multiple
bonds -
a type of isomerism
characteristic of compounds with more than 3 carbon atoms and
having double or triple bonds.
-
functional
group-
a type of isomerism
characteristic of oxygen- and nitrogen-containing organic
compounds.
-
Interclass isomerism
(isomerism of functional
groups)
is characteristic of compounds
that have the same general formula, but belong to different classes
and have different chemical and physical
properties.
2.4. Spatial
isomerism
Spatial isomers are substances
with the same composition and chemical structure, but with a
different spatial arrangement of atoms in a molecule. Types of
spatial isomerism - geometric (cis-trans) and optical
isomerism.
1. Geometric isomerism (or
cis-trans-isomerism).
Geometric isomerism is
characteristic of compounds in which the position of substituents
relative to the plane of the double bond or cycle is different. For
example, for alkenes and
cycloalkanes.
The double bond does not have
free rotation around its axis.
Therefore, substituents at
carbon atoms in a double bond can be located either on one side of
the double bond plane (cis isomer), or on opposite sides of the
double bond plane (trans isomer). In this case, no rotation can be
obtained from the cis-isomer of the trans-isomer, and vice
versa.
For example, butene-2 exists
as cis- and trans-isomers.
1,2-Dimethylpropane also forms
cis-trans isomers:
Geometric isomers differ in
physical properties (boiling and melting points, solubility, dipole
moment, etc.). For example, the boiling point of cis-butene-2 is
3.73°C, and of trans-butene-2
0.88°C.
At the same time, cis-trans
isomerism is characteristic of compounds in which each carbon atom
in the C=C double bond (or in the cycle) has two different
substituents.
For example, in the butene-1
molecule CH2=CH-CH2-CH3, the substituents at the first carbon atom
in the double bond (two hydrogen atoms) are the same, and butene-1
does not form cis-trans isomers. But in the butene-2
CH3-CH=CH-CH3 molecule, the substituents on each carbon atom in
the double bond are different (hydrogen atom and methyl group CH3),
so butene-2 forms cis- and
trans-isomers.
Thus, for compounds of the
type СH2=СHR and СR2=СHR', cis-trans isomerism is not
typical.
2. Optical
isomerism
Optical isomers are spatial
isomers, the molecules of which are related to each other as an
object and an incompatible mirror image.Optical isomerism is
characteristic of molecules of substances having an asymmetric
carbon atom. An asymmetric carbon atom is a carbon atom bonded to
four different substituents.
Such molecules have optical
activity - the ability to rotate the plane of polarization of light
when a polarized beam passes through a solution of a substance. For
example, 3-methylhexane forms optical
isomers:
Conclusion
In short, isomers are
substances with the same molecular formula, but different structure
and different physical and chemical
properties.
There are several types of
isomerism. Structural isomerism is caused by a different order of
addition of carbon atoms in the molecule. Structural isomers may
differ in the structure of the carbon skeleton, the plural bonds
and the location of substituents, as well as may belong to
different classes of organic
compounds.
Spatial isomerism arises from
the different positions of atoms in space. The order of atomic
bonds of geometric isomers is the same, but differs in the spatial
arrangement that determines their different properties. Optical
isomerism is characteristic of substances containing an asymmetric
carbon atom (c), that is, a carbon atom attached to four different
substituents. Optical isomers do not match their mirror
image.
References
-
Rudzitis G.E. Chemistry.
Fundamentals of General Chemistry. Grade 10: textbook for
educational institutions: basic level / G. E. Rudzitis, F. G.
Feldman. – 14th edition. – M.: Enlightenment,
2012.[
RUSSIAN]
-
Chemistry. Grade 10. Profile
level: textbook. for general education institutions / V. V. Eremin,
N. E. Kuzmenko, V. V. Lunin et al. - M.: Bustard, 2008. - 463
p. .[
RUSSIAN]
-
Chemistry. Grade 11. Profile
level: textbook. for general education institutions / V. V. Eremin,
N. E. Kuzmenko, V. V. Lunin et al. - M.: Bustard, 2010. - 462
p. .[
RUSSIAN]
-
Khomchenko G. P., Khomchenko
I. G. Collection of problems in chemistry for applicants to
universities. - 4th ed. - M.: RIA "New Wave": Publisher Umerenkov,
2012. - 278 p. .[
RUSSIAN]