Isomerism Flashcards
isomerism
phenomenon of existing 2 or more molecules with same molecular formula, but different structural formulas and diff phy and chem props
isomers
molecules that have same molecular formula but differ in properties and arrangement of atoms in the molecule
structural isomerism
arises from difference in arrangement atoms within the molecule and is independent of position of atom in the space around the molecule
classification of structural isomerism
chain position functional group metamerism tautomerism ring chain
classification of isomerism
structural
stereo
chain or nuclear isomerism
diff arrangement of C atoms in a C chain
position isomerism
diff position of atoms or groups in C chain which remains intact in isomers
functional group
have different func grps and thus belong to homologous series
metamerism
isomers are formed when 2 valencies of a hetero atom are satisfied by diff alkyl grps
tautomerism
isomers are co existing in eqm
ring chain isomerism
arises from diff in modes of linkages of C chains to get straight chain and cyclic isomers
geometrical isomers
possess the same structural formula but differ in their spatial arrangement of atoms or groups around double bond
stereo isomerism
same structural formula but differ in spatial arrangement within the molecule
2 types of configurational isomerism
geometrical
optical
2 types of stereo isomers
configurational
confirmational
optical activity
phenomenon of rotating the plane polarized light
dextro rotatory, laevo rotatory
dextro: rotates plane polarized light to right
laevo: to left
chiral C atom
4 valencies are satisfied by diff atoms and grps
enantiomers
optically active isomers form non super imposable mirror imgs
conditions of optical isomerism
1) molecule shouldnt have plane of symmetry
2) should not super impose on mirror img
characteristics of enantiomers
1) identical props in all respects except in interaction with plane polarized light
2) identical chem props but differ in reactivity with optical active reagents
3) diff bio props
diastereomers
stereoisomers which are not mirror imgs of a compound
racemic mixture
equimolecular mixture of dextro and laevo forms of an optically active substance
resolution of racemic mixture
separating d and l forms from mixture
conformational isomerism
isomerism arising from the diff in conformation of the isomers
2 forms of conformation
staggered
eclipsed
types of projections of conformation
seahorse
newman
haworth
fischer
proximal
front C atom in newman projection
distal
back atom in newman projection
2 forms in which cyclohexane can exist
boat form
chair form
why do substituents larger than H generally suffer greater steric crowding when they are oriented axial rather than equatorial
axial bonds are parallel to each other
2 principles of conformation in cyclohexane
1) chair conformations are generally more stable
2) substituents on chair conformers prefer to occupy equatorial positions due to increased steric hinderance of axial locations
conformation
shape that a molecule can adopt due to the rotation around one or more single bonds
angle strain
strain due to deviation from one or more ideal bond angles
torsional strain
strain caused by van der Waals repulsion which can be reduced or eliminated by rotation around a single bond
