Structural isomers and stereoisomers configuration | types of isomers | isomers | isomerism

types of isomers and their definition
and their representation

1. CHEMISTRY ISOMERISM STRUCTURAL ISOMERS AND STEREOISOMERS CONFIGURATION

2. STRUCTURAL ISOMERS A  structural isomer , or  constitutional isomer, is a type of isomer in which molecules with the same molecular formula have different bonding patterns and atomic organization, as opposed to stereoisomers in which molecular bonds are always in the same order and only spatial arrangement differs. There are multiple synonyms for structural isomers.

3. THREE CATAGORIES OF STRUCTUARL ISOMERS SKELETAL ISOMERS (CHAIN ISOMERS) POSITIONAL ISOMERS (REGIOISOMERS) FUNCTIONAL ISOMERS

4. SKELETAL ISOMERS (CHAIN ISOMERS) In  chain isomerism , or  skeletal isomerism , components of the (usually carbon) skeleton are distinctly re-ordered to create different structures. Pentane exists as three isomers:  n -pentane (often called simply "pentane"), isopentane (2-methylbutane) and neopentane (dimethylpropane). n -pentane isopentane neopentane

5. POSITIONAL ISOMERS (REGIOISOMERS) pentan-1-ol pentan-2-ol pentan-3-ol In  position isomerism  ( Regio isomers ) a functional group or other substituent changes position on a parent structure. In the table below, the hydroxyl group can occupy three different positions on an  n -pentane chain forming three different compounds.

6. FUNCTIONAL ISOMERS Functional isomers  are structural isomers that have the same molecular formula (that is, the same number of atoms of the same elements), but the atoms are connected in different ways so that the groupings are dissimilar. These groups of atoms are called functional groups, functionalities. Example: cyclohexane and 1-hexene both have the formula C 6 H 12 .These two are considered functional group isomers because cyclohexane is a cycloalkane and 1-hexene is an alkene. cycloalkane 1-hexene

7. STEREOISOMERS In stereochemistry,  stereoisomerism , or  spatial isomerism , is a form of isomers in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer. They are two types: Optical isomerism(Enantiomers) Geometrical isomerism

8. Enantiomers Enantiomers, also known as optical isomers, are two stereoisomers that are related to each other by a reflection: they are mirror images of each other that are non-superimposable. Human hands are a macroscopic analog of this. Every steroidogenic center in one has the opposite configuration in the other. Two compounds that are enantiomers of each other have the same physical properties, except for the direction in which they rotate polarized light and how they interact with different optical isomers of other compounds. As a result, different enantiomers of a compound may have substantially different biological effects. Pure enantiomers also exhibit the phenomenon of optical activity and can be separated only with the use of a chiral agent. In nature, only one enantiomer of most chiral biological compounds, such as amino acids (except glycine , which is achiral) , is present. An optically active compound shows two forms : D(+),D(-)

9. CHIRILITY  In compounds in which an atom that is connected to 4 different substituent groups. This atom is called a-symmetric atom or a stereo center. Those compounds are called chiral compounds.

10. OPTICAL ACTIVITY The interaction with light is called optical activity and enantiomers are often called optical isomers. Optical rotation is measured with the polarimeter.

11. REPRESENTATION SAWHORSE PROJECTION NEWMAN PROJECTION

12. FISHER PROJECTION It is a formula which represent tetrahedral carbon atom and their substituent's in two dimensions. The molecule is drawn in the form of cross. The tetrahedral carbon is the plane of the paper at the center of cross. Atoms connected to the tetrahedral carbon by horizontal bonds are behind the plane of the paper. Atoms connected to the tetrahedral carbon by vertical bonds in front of the plane of the paper. Fisher projection tell us the absolute configuration then we get R and S enantiomers.

13. DIASTEREOMERS Diastereomers  (sometimes called  diastereoisomers ) are a type of a stereoimers. Diasteoreomers are defined as non-mirror image non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocentre and are not mirror images of each other. When two diastereoisomers differ from each other at only one stereocenter they are epimers. Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two. Diastereomerism can also occur at a double bond, where the cis vs trans relative positions of substituents give two non-superimposable isomers. NOMENCLATURE Cis -Trans nomenclature E-Z nomenclature Syn -Anti system of nomenclature.

14. Cis-Trans nomenclature In this, compound of the type CH2 = CH2 can exist in the following two forms due to frozen rotation about carbon - carbon double bond. The isomers in which the identical groups are on the same side of the double bond is called cis which the group are on opposite side called as trans. cis-1,2-dichloroethene trans-1,2-dichoroethene

15. E-Z nomenclature  When all the four substituents are different cis- trans type of isomerism cannot be applied. In this type E-Z system of nomenclature is applied based upon the sequence rules of Cahn Ingold and prelog for naming. Higher priority is assigned to atoms of higher atomic number. Z = Zusammen (same side) • E = (opposite side)

16. Syn -Anti system of nomenclature When C=N is formed by reaction of aldehyde with NH2-G then H on carbon and substituent's on nitrogen are on the same side then configuration is Syn and when on opposite sides and configuration is anti where G may be H,R,OH,NH,NHph and NHCONH2.

17. Resources Wikipedia thank you