Isomers

Chain isomerism Positional isomerism Functional group isomerism same molecular formula different structural formula

different arrangement of carbon skeleton

different location of substitutional/functional groups on C chain

different functional groups

Criteria Presence of chiral center cis trans isomerism same molecular and structural formula but different spatial 3d arrangement of atoms

have different physical properties due to difference in SA of contact between molecule but have the same chemical properties due to the fact that they have the same functional group

types 1. alcohols (OH), ethers(OCH3) CnH2n+2O 2. alkenes and cycloalkenes CnH2n 3.carboxylic acids(OH-C=O) and esters(O-C=O) CnH2nO2 4. aldehydes(H-C=O )and ketones( CH3-C=O) CnH2nO have different physical and chemical properties

two conditions for it to exist restricted rotation about a bond can be due to 1. C=C in a str8 chain 2. Ring structure two different groups on each of the carbon atoms with restricted atoms 3. cyclic alkenes do not exhibit cis trans despite fulfilling both conditions

have identical atoms groups of atoms on the same side of the double but never on the same carbon

have identical atoms/groups of atoms on diagonal sides of the double bond

same chemical but different physical 1.due to differences in polarity

a molecule with ‘m’ cis trans C=C has a max of 2^m stereoisomers

exists when molecules contain at least one chiral centre causing them to lack a point and plane symmetries

if C atom is attached to 4 diff atoms/groups of atoms labelled with a *

pair of compounds with same connectivity but opposite 3d shapes. non superimposable images mirror images of each others

• enantiomers rotate the plane of plane polarised light by equal angles in the opposite directions when equal conc of enantiomers are being analysed similar chemical properties(exc when interacting w a chiral mol.) and physical properties(exc in the direction in which they rotate plan polarised light) different different biological properties 2.racemic mixture mixture containing equal conc of enantiomers the equal but opp rotation of plane polarised light by each enantiomers results in net zero optical activity. mixture is optically inactive despite having chiral molecules

a molecule with n chiral centers has a max of 2^n stereoisomers

• might have isomers that are identical/superimposable

contains 2 chiral centers but is superimposable on its mirror image as it has a plane of symmetry optically inactive as the effect on the plane polarised light by each half of the mol. is equal in magnitude but opposite in directions. Hence they cancel each other out to give a net zero effect on plane polarised light

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the arrangement of atoms between a pair of enantiomers are recognised • enantiomers can interact differently with the chiral receptor cells in taste buds to detect taste • enantiomers can interact differently with chiral receptor cells in the nose to detect smell • drugs work by interacting with the appropriate receptor site via IMF which are very specific