Isomerism Flashcards
How many isomers are there for C4H10, C5H12, C6H14 and C7H16?
2, 3, 5 and 9
Chain Isomerism
Compounds having the same molecular formula but different selection of principal carbon chain
Position Isomerism
Compounds having same molecular formula but different position of the functional group, substituent or multiple bond
Functional Isomerism
Compounds having the same molecular formula but different types of functional groups are present
Metamerism
Different numbers of carbon atoms present bivalent atom or the functional group present in them
Tautomerism
Special case of functional isomerism that are in dynamic equilibrium with each other
Conformers
Compounds that are obtained when a molecule is rotated along C-C bond
Staggered and Eclipsed form of ethane
Staggered, dihedral angle is 60 degree and eclipse, dihedral angle is 0 degree.
Skew conformers
All conformers of C2H6 except for staggered and eclipsed form
Stability of conformers of n-Butane
Anti-staggered(180)> Gauche(60)> Partially Eclipsed(120)>Fully eclipsed(0)
Steric and Torosional Strain
Repulsion due to bulky group and repulsion between the bond pair
Stability of conformers of cyclo-hexane
Chair> Twist Boat> Boat> Half Chair
Stereoisomers
Compounds having the same molecular formula, but different orientation of atoms in space
Optical Isomers
Compounds having same molecular formula, but they differ from each other based on optical rotation or optical activity
Optical Activity
Compounds having same molecular formula, but one of them is dextrorotatory and another one is levorotatory
Conditions for a compound to be chiral atom
- It must be sp2 hybridise
- All four valencies must be satisfied by different atoms on group
Conditions for asymmetric and desymmetric molecules
POS, COS are absent
Condition for opitcal isomerism
A compound must be dissymmetric to exhibit optical isomerism
Object and its mirror image should be non-super imposable of each other.
Allene
Compounds having even number of consecutive double bonds
Cumelenes
Compounds containing odd number of consecutive double bonds and they do not exhibit optical isomerism
Racemic mixture
Equi-molar mixture of object and its mirror image
Enantiomers
Objects and their non-superimposable mirror images are enantiomers to each other.
They have same physical properties.
Meso Form
Form of optically active substance which will have POS and COS in it. They should be optically inactive.
R and S configuration
When lowest priority is on vertical line, then clockwise is R form and anti-clockwise is S-form
When lowest priority is on horizontal line, then clockwise is S-form and anti-clockwise is R-form.
Total optical isomers if the compound is unsymmetrical having ānā chiral centre
2^n
Stereogenic Area
Part of the molecule which shows stereoisomerism is known as the stereogenic area.
D and L form
If the principal functional group is on the top and the hydroxyl group w.r.t last chiral is present on the right side of the plane, then it is D-form and if it is present on the left, then it is L-form.
E and Z form
When the priority due to CIP rule is on the same side, then it is Z form and on the opposite side, then it is E form.
If the symmetry is present, then geometrical isomerism is
2^n
