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Transcript of Isomerism Ravi
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A term paper submitted for the partial fulfillment of the course
CHE 101
Submitted to: Submitted by:
Mr. HARMINDER SINGH Name: Ravi Ranjan
Deptt. Of Chemistry Roll. RE6901A14
Reg.No:10900841
Section: E6901
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ACKNOWLEDGEMENT
I would like to express the deepest appreciation to my subject teacher
Mr. Harminder Sir, who gave me this term paper through which I was able to interact with
the mysterious chemistry world. Sir you are a complete genius. You continuously &
convincingly enriched our knowledge throughout the session. Without Your guidance
and persistent help this dissertation would not have been possible.
My friend Rana Pratap Singh needs special thanks as he gave me his laptop for the project.
Without you, I would not have imagined to do this project.Sorry for taking so much
time.
Google also deserves thanks. Seriously nothing is perfect in this world except Google. Had
there been not Google, what we would have done.
Last but not the least, my parents for their evergreen love, support and trust on me. You have
a special place in my heart for inspiring the talent in me.
Thanks.
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Table of contents:
S. No. Contents Page No.(From- To)
1. Introduction of isomerism 4
2. Isomerism in Organic Chemistry 4
3. Types of Isomerism in Organic Chemistry 4-16
4. Isomerism in Inorganic Chemistry 17
5. Types of Isomerism in Inorganic Chemistry 17-21
6. References 22
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1. Introduction
Isomerism
Similar molecular formula of different compounds having different chemical or physicalproperties due to change in the arrangement of atoms is called isomerism.
Different structures are called isomers of each other.
For the first time isomerism was noticed in 1827, when Friedrich Woehler prepared cyanic acid
and found that although its elemental composition was identical to fulminic acid its properties
were quite different. From this it was found that chemical compounds could be different only
when they had different elemental compositions.
2. Isomerism in Organic Chemistry
It is one of the most important characteristics shown by the organic compounds.
The concept of isomerism illustrates the fundamental importance of molecular structure
and shape in organic chemistry. Carbon is the seventeenth most abundant element found
on the earths crust. It forms compounds than any other element except hydrogen.
3. Types of Isomerism in Organic Chemistry
In organic chemistry, isomerism is divided into following types:
I. STRUCTURAL ISOMERISM: Similar molecular formula of different compounds
but different chemical or physical properties due to change in the connectivity of
atoms is known as Structural Isomerism.
It is sub-divided into:
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a) Chain Isomerism[1]: Similar molecular formula of different compounds but
different chemical or physical properties due to change in the length of carbon
chain. It is also called skeletal isomerism.
Example:
C5H12 :
C4H9Br:
pentane 2-methylbutane
http://www.creative-chemistry.org.uk/molecules/chain.htmhttp://www.creative-chemistry.org.uk/molecules/chain.htm -
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C5H12:
&
b) Positional Isomerism: Similar molecular formula of different compounds but
different chemical or physical properties due to change in the position (locant
nos. of functional group, multiple bonds or side chain). In positionalisomerism, parent system always remains the same.
Example:
C4H8:
CH3-CH2-CH=CH2 & CH3-CH=CH-CH3
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c) Functional Group Isomerism [2]: Similar molecular formula of different
compounds but different chemical or physical properties due to change in the
functional group. A functional group isomer can be identified using infrared
spectroscopy.
Example:
Cyclo hexane & 1-hexene
&
C2H6O:
CH3-O-CH3 & CH3CH2-O-H
Di methyl ether Ethanol
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C4H8&C4H6:
d) Ring-Chain Isomerism: It is a type of functional group isomerism. This type
of isomerism is due to different modes of linking of carbon atoms, i.e., the
isomers possess either open chain or closed chain structures. For ring-chain
isomerism, the open structure must have at least one pi bond.
Examples:
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e) Metamerism: Similar molecular formula of different compounds but different
chemical or physical properties due to change in the molecular formula of
alkyl groups around polyvalent functional group. There is always same
functional group in all metamers.
Examples:
Diethyl ether & Methyl propyl ether
CH3-CH2-O-CH2-CH3 & CH3-O-C3H7
Diethyl amine & Methyl propyl amine
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C2H5-NH-C2H5 & CH3-NH-C3H7
Diethyl Ketone & Methyl Propyl ketone
f) Tautomerism: Phenomena in which any compound can exist into two
functional isomers are called tautomerism. Different isomers are called
tautomers of each other in which position of any one atom (generally H) may
be different. In other words we can say that when proton (H +) migrates from
one polyvalentatom to other polyvalent atom, the isomerism aroused is called
tautomerism.
The word tautomerism was proposed in 1886 to describe the mobile
equilibrium between two compounds having weakly bonded hydrogen atom.
It is basically of two types:
Keto-Enol tautomerism &
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Base Catalyzed tautomerism
Example:
Tetrahydronaphthalenedione:
2-aminopyrroles[3]:
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II. STEREO ISOMERISM: Isomerism aroused due to the change in the arrangement of
atoms in the space without changing the connectivity is known as Stereo Isomerism.
They differ only in the three-dimensional orientations of their atom in space.
It is further divided into:
a) Geometrical Isomerism: This isomerism arises due to the restricted rotation of
doubly bonded carbon. They can also arise from ring structures where rotation
of bond is restricted.
When the substituent groups are attached in the same direction, the
isomerism aroused is called cis-isomerism while when the
substituent groups are attached in the opposite direction, the isomerism
aroused is called trans-isomerism.
Generally Trans form is more stable than cis form due to less steric
repulsion.
When there are more than two different substituent groups on double
bond carbon than cis/trans form is not effective, and then E/Z system
is used. Z (zusammen) means together and is similar to cis form
whileE(entgegen) means opposite and is similar to Trans form.
A molecular configuration is assigned E/Z naming on the basis of
certain priority rule. The atom with higher atomic number is given
higher priority. If both the higher priority groups are on the same side,
the system is Z form & if on the opposite sides, it is E form.
Example:
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Cis-2-pentene & trans-2-pentene:
&
Trans-Fumaric Acid & Cis-Maleic Acid[4]:
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cis-1,2-dichloroethene & trans-1,2-dichloroethene:
&
(E)-But-2-ene & (Z)-But-2-ene
b) Optical Isomerism: Isomerism in the organic compound having same
molecular formula but rotates the plane polarized light in different direction is
called optical isomerism. Optical isomers are named like this because of their
effect on plane polarized light.
Optical isomers can occur when there is an asymmetric carbon atom. An
asymmetric carbon atom is one which is bonded to four different groups. The
term optical activity is derived from the interaction of chiral materials with
polarized light. This property was first observed by Jean-Baptiste Biot in
1815.
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Representation
I. Wedge-Dash formula : It is commonly used for cyclic system.
As with straight chains, cyclic Wedge-Dash Notation has two
bonds drawn in the plane of the page (sticks), one bond drawn
coming toward us, out of the page and above the ring
(wedged), and one bond drawn going away from us, behind the
page and below the ring (dashed). Example
II. Fischer Projection: It is the 2-d representation of 3-d organic
molecules by projection. All bonds are represented as
horizontal or vertical line. In a Fischer projection, all horizontal
bonds project toward the viewer, while vertical bonds project
away from the viewer.
Naming Conventions :
I. By R & S configuration: Priority is assigned on the basis of
atomic number. It labels each chiral centerR orSaccording to
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a system by which its substituent are each assigned a priority,
according to the Cahn Ingold Prelog priority rules (CIP), based
on atomic number. If move from higher priority group to
lower in clockwise direction, the configuration is R & if we are
moving in the anticlockwise direction, the configuration is S.
II. By Optical activity: when the plane of PPL is rotated in
clockwise direction it is dextro (D) form while when the
rotation is in the anti-clockwise direction it is laevo (L) form.
Examples:
Butan-2-ol:
2-hydroxypropanoic acid (lactic acid):
2-aminopropanoic acid (alanine):
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4. Isomerism in Inorganic Chemistry
It is one of the important characteristics of the transition metals to form complexes which
are called Coordination Compounds. In inorganic chemistry, coordination compounds
often show various types of the Isomerism.
5. Types of Isomerism in Inorganic Chemistry
As in the case of organic compounds, coordination compounds show two main types of
Isomerism:
I. STRUCTURAL ISOMERISM: It occurs due to the difference in the ligands.
It is further divided into:
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a) Ionization Isomerism: in this, coordination sphere must be cationic. The
anionic ligand present must be different from the anion present outside of
the coordination sphere. This isomerism arises, due to exchange of anionic
ligand with anion present outside of the coordination sphere.
Example:
[Co(NH3)5Cl]SO4 & [Co(NH3)5SO4]Cl
[Co(NH3)4Br2]Cl & [Co(NH3)4BrCl]Br
b) Coordination Isomerism: this isomerism arises due to exchange of ligand
between two coordination spheres. Both cation and anion must be
complex.
Example:
[Cr(NH3)5(CN)] & [Cr(NH3)(CN)5]
[Cr(NH3)4(CN)2] & [Cr(NH2CN)4]
c) Hydrate Isomerism: It arises due to the exchange of H2O within
coordination sphere & outside of it. H2O must be present as a ligand.
Example:
[Co(H2O)6]Cl3 & [Co(H2O)5Cl]Cl2.H2O
[Co(H2O)4Cl2]Cl.2H2O &
[Co (H2O)3 Cl3].3H2O
d) Linkage or Salt Isomerism: this type of isomerism is shown by the
compound having ambidentate ligand.
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Example:
[Co(NH3)5NO2]Cl2 &
[Co (NH3)5ONO]Cl2
e) Ligand Isomerism: this isomerism arises when more than one structures
are all possible for any ligand.
Example:
[Fe(H2O)2 C3H6(NH2)2 Cl2]
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f) Coordination Position Isomerism: It arises due to the exchange of ligand
associated with the central metal atom. In compounds, bridge ligands must
be present.
Example:
II. STEREO ISOMERISM : It arises due to the difference in the orientation of the
ligands.
It is sub-divided into:
a) Geometrical Isomerism [5]: If due to exchange of ligand within
coordination sphere changes arrangement in compound then aroused
isomerism is called as Geometrical Isomerism. Tetrahedral complex do
not show geometrical isomerism, only square planar & octahedral
complexes show geometrical isomerism.
If the identical ligands are aligned with an angle of 90o
with the central
metal, it is cis form while if the identical ligands are aligned at an angle of
180o with the central metal, it is Trans form. Example:
[PtBrClNH3(py)]
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Cis-dichloro tetra ammine cobalt(III) &Trans -dichloride tetra
ammine cobalt (III)
b) Optical Isomerism: Coordination compounds which are non super
imposable mirror images of each other are called as optical isomers or
enantiomers. They are of two typesd & l and they do not have any
plane of symmetry.
Square planar complexes do not show optical isomerism only tetrahedral
complex of type Mabcd (where M is the central metal and a, b, c, d ligands)
show optical isomerism.
Example:
[Co(en)2Cl2]+
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Mirror image
[Fe(Ox)3]3-:
Mirror image
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6. Reference Site
1> http://www.creative-chemistry.org.uk/molecules/chain.htm#
2>
http://en.wikipedia.org/wiki/Functional_isomer#Functional_group_isomerism
http://www.creative-chemistry.org.uk/molecules/chain.htmhttp://en.wikipedia.org/wiki/Functional_isomer#Functional_group_isomerismhttp://www.creative-chemistry.org.uk/molecules/chain.htmhttp://en.wikipedia.org/wiki/Functional_isomer#Functional_group_isomerism -
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3> http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-
4TTMN7R-
1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c
&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_ver
sion=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317
532
4>http://images.google.co.in/imgres?
imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.j
pg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-
acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16
&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&pr
ev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1
5> http://wwwchem.uwimona.edu.jm:1104/courses/IC10Kiso.html
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://images.google.co.in/imgres?imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.jpg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&prev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1http://images.google.co.in/imgres?imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.jpg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&prev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1http://images.google.co.in/imgres?imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.jpg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&prev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1http://images.google.co.in/imgres?imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.jpg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&prev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1http://images.google.co.in/imgres?imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.jpg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&prev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1http://images.google.co.in/imgres?imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.jpg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&prev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1http://images.google.co.in/imgres?imgurl=http://i.ehow.com/images/GlobalPhoto/Articles/5340486/337263_Full.jpg&imgrefurl=http://www.ehow.com/about_5340486_structure-fumaric-acid.html&usg=__BJlAigrx4B1dtqyKQwATWP_dAhs=&h=400&w=600&sz=16&hl=en&start=9&um=1&tbnid=ZHQqhcBcou0tQM:&tbnh=90&tbnw=135&prev=/images%3Fq%3Dfumaric%2Bacid%2Bstructure%26hl%3Den%26um%3D1http://wwwchem.uwimona.edu.jm:1104/courses/IC10Kiso.htmlhttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6THS-4TTMN7R-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1113044003&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=a1f0fa3ef693f916361207b13d317532http://images.goo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