Isomerism-1 Flashcards
what are isomers and what is isomerism
Two or more than two compounds having the same molecular formula but different physical/chemical or
both properties are called isomers and the phenomenon is called isomerism.
classification of isomers
(i) structural isomerism
- Chain isomers
- Positional isomerism
- Functional isomerism
- Ring chain isomerism
- Metamerism
(ii) Stereoisomerism
- Geometrical Isomerism
- Optical Isomerism
what is chain isomerim
when two cpds have same molecular formula, same functional group but different arrangement of carbons in the parent chain .
iso- one methyls carbons surrounding the second carbon
neo- two methyl carbons surrounding the second carbos
min no of carbon for alkane= 4
min no of carbon for alkene= 4
min no of carbon for alkyne=5
what is positional isomerism
The compounds which have same molecular formula, same functional group, same parent carbon chain but
different position of functional group or multiple bond or substituents, show position isomerism.
min no of carbon for alkane=6
min no of carbon for alkene=4
min no of carbon for alkyne=4
what is iupac name for triptane
2,3,3,- triimethylbutane
what is ringchain isomerism
Same molecular formula but different mode of linking (open chain & closed chain) of carbon atoms..
alkene= cycloalkane
alkyne/alkadiene=cycloallkene
ringchain isomers are also functional isomers but priority is fr ring chain isomers
what is functional isomerism
Same molecular formula but different functional groups.
- alcohols, ethers
- acids, esters
- aldehydes,ketones
- nitro and nitrite
- cyanid and isocyanide
- primary,secondary,tertiary amines
- phenolic, alcoholic (benzene ring) cpds
alkyl halides do not show func isomerism
what is metamerism
Same molecular formula, same polyvalent Functional group but different alkyl groups attached to polyvalent
Functional group.
Polyvalent Functional group [Which have more than one valency] are :
ether, sulphur
-C-O-
II
O
ketone, acid anhydride
-C-N H -
II
O
-NH-
-N-
I
what are the two types of stereoisomerism
(i) Configurational Isomerism
- Geomtircal isomerism
- Optical isomerism
(ii) Conformational Isomerism
what is geometrical isomerism
Stereo isomer which cannot interconvert at room temperature due to restricted rotation known as
Geometrical isomerism.
Alkenes ( >C C<), oximes (>C N—) and azo compounds [—N N—] etc., show G. I. due to restricted
rotation about double bond and (ii) cycloalkanes show G. I. due to restricted rotation about single bond in
ring.
what is the condition for geomtetrical isomerism in alkenes
Each sp2 hybiridised carbon must have individuallly differentgrps.
If any of the double bonded ccarbons have two same groups bonded with it, then geomtrical isomerism cannot occur
what is cis trans system
If same groups are at same side then cis and if same groups are at different side then trans.
what are components of E-Z nomenclatur e
E (Entgegen) : When high priority groups are at opposite side.
Z (Zusamman) : When high priority groups are at same side.
give the cip rules
they help in determining the high priority and low priority grps
(i) higher the atomic number, more priority
(ii) if two grps have same atomic number then consider the next atom in the chain
(iii) consider miltiple bonds as single bonds
(iv) the grp with higher mass, has more priortiy
Geometrical isomerism in oximes
Oximes show G. I. due to restricted rotation about double bond.
l Only those oximes show Geometrical isomerism in which sp2 carbon have two different groups.
syn= if the H and OH are present on the same side
anti= if H and OH are present on opposite sids
