E and Z
Key Questions
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Answer:
E-ZE−Z isomerism occurs because there is restricted rotation about double bonds.Explanation:
In
E-ZE−Z isomers you must have:- restricted rotation, often involving a
"C=C"C=C double bond - two different groups on one end of the bond and two different groups on the other end.
For example, an alkene such as but-2-ene has two different groups on each alkene carbon.
It can exist as
E-ZE−Z isomers that differ in the positions of the substituents on the double-bonded atoms.
The substituents can be given "priorities", with atoms with higher atomic numbers given higher priorities (the Cahn-Ingold-Prelog rules).
If the highest priority groups for each carbon are on the same side of the molecule, we have the
ZZ isomer.If the highest priority groups for each carbon are on opposite sides of the molecule, we have the
EE isomer.
Ernest Z.
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2
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Jun 11 2015
- restricted rotation, often involving a
-
Answer:
E-ZE−Z isomerism is a type of stereoisomerism that exists because of restricted rotation about double bonds.Explanation:
In stereoisomers, the atoms are joined in the same order, but they have a different spatial arrangement.
In
E-ZE−Z isomers you must have:- restricted rotation, often involving a
"C=C"C=C double bond - two different groups on one end of the bond and two different groups on the other end.
An alkene such as but-2-ene has two different groups on each alkene carbon.
It can exist as
E-ZE−Z isomers that differ in the positions of the substituents on the double-bonded atoms.The substituents can be given "priorities", with atoms with higher atomic numbers given higher priorities (the Cahn-Ingold-Prelog rules).
If the highest priority groups for each carbon are on the same side of the molecule, we have the
ZZ isomer.If the highest priority groups for each carbon are on opposite sides of the molecule, we have the
EE isomer.One way to remember the designations is to think of
ZZ as Zame Zide (same side).Since
"CH"_3CH3 has higher priority than"H"H , it is pretty easy to determine that the butene isomers above areEE andZZ , respectively.But what about the isomers of 2-methylbut-2-enoic acid (below)?
"CH"_3CH3 has higher priority than"H"H , and"COOH"COOH has higher priority than"CH"_3CH3 .Angelic acid has the higher priority groups on the same side, so it is the
ZZ isomer.Tiglic acid has the higher priority groups on opposite sides, so it is the
EE isomer.
Ernest Z.
·
5
·
Jun 11 2015
- restricted rotation, often involving a