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Difference between sterioisomers and structural isomers!?

According to textbook:

Sterioisomer : same structural formula but different 3d arrangement of atoms in space

structural isomer : same molecular forumla but different arrangement of atoms

To me they are identical ! obviously they are not

Please someone explain how they are different! :smile:
+rep
Original post by arvin_infinity
According to textbook:

Sterioisomer : same structural formula but different 3d arrangement of atoms in space

structural isomer : same molecular forumla but different arrangement of atoms

To me they are identical ! obviously they are not

Please someone explain how they are different! :smile:
+rep


This sort of explains it well. :smile:
Reply 2
Avatar for whotosee
whotosee
1
You know the difference between structural and molecular formula?
Here's two websites that explain the two things well. Let me know if you don't understand it!

Sterioisomer
http://www.chemguide.co.uk/basicorg/isomerism/geometric.html

Structural isomerism
http://www.chemguide.co.uk/basicorg/isomerism/structural.html
Original post by arvin_infinity
According to textbook:

Sterioisomer : same structural formula but different 3d arrangement of atoms in space

structural isomer : same molecular forumla but different arrangement of atoms

To me they are identical ! obviously they are not

Please someone explain how they are different! :smile:
+rep


Structural isomers: same molecular formula, but different structural formulas. You have 3 types of structural isomer; chain, positional and function group.

Structural isomerism deals with the different arrangement of compounds, whereas, stereoisomerism has the same arrangement but a different spacial orientation within the arrangement. That is the difference.

There are 2 types of stereoisomerism; geometric and optical.

Edit: If you need further explanation, then please let me know.
Original post by thegodofgod
This sort of explains it well. :smile:


Like it :biggrin: well answered

whotosee


You know the difference between structural and molecular formula?
Here's two websites that explain the two things well. Let me know if you don't understand it!




Tullia


There are 2 types of stereoisomerism; geometric and optical.

Edit: If you need further explanation, then please let me know.



You have reached the limit of how many posts you can rate today!!!! OH well, will +rep you later :wink:


So lets look at this example:




They both have the same molecular formula and same arrangement of atoms and therefore same structural formula

But they have different arrangement of atoms in space
So basically structural is in 2D but sterioisomer is in 3D
Original post by arvin_infinity
Like it :biggrin: well answered







You have reached the limit of how many posts you can rate today!!!! OH well, will +rep you later :wink:


So lets look at this example:




They both have the same molecular formula and same arrangement of atoms and therefore same structural formula

But they have different arrangement of atoms in space
So basically structural is in 2D but sterioisomer is in 3D


Yeh, you could say that, since Optical isomers (a type of stereoisomer) are non-superimposable and are mirror images of each other. :smile:
Reply 6
Avatar for Gaz94
Gaz94
4
Structural isomers are compounds with the same molecular formula but a different structural formula.

Stereoisomers are isomers with the same structural formula but with a different arrangement of atoms in space.

E/Z isomerism is an example of steroisomerism in the terms of restricted rotation about a double bond. With the requirement for two different groups to be attached to each Carbon of the C=C group.

Cis/Trans isomerism is a special case of E/Z isomerism where two substituent groups are the same.

Whenever there is E/Z isomerism there is Cis/ Trans they are basically the same thing but E/Z is a more modernly used term.
Original post by arvin_infinity
So basically structural is in 2D but sterioisomer is in 3D


You seem to have the understanding of the concept, and so it really is thinking of it in a way that works best for you. As far as I can see, there is nothing wrong with thinking about it in that way.

Original post by Gaz94
E/Z isomerism is an example of steroisomerism in the terms of restricted rotation about a double bond. With the requirement for two different groups to be attached to each Carbon of the C=C group.

Cis/Trans isomerism is a special case of E/Z isomerism where two substituent groups are the same.

Whenever there is E/Z isomerism there is Cis/ Trans they are basically the same thing but E/Z is a more modernly used term.


It isn't a difficult concept to understand, but it is highly unlikely that anything beyond the cis-trans system will be required for A-level. This is why cis-trans are what are generally taught at A-level.
Reply 8
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Gaz94
4
Original post by Tullia
It isn't a difficult concept to understand, but it is highly unlikely that anything beyond the cis-trans system will be required for A-level. This is why cis-trans are what are generally taught at A-level.


On the OCR F322 specification you mostly need to know E/Z isomerism. Also show examples of Cis/ Trans isomerism. As i said they are the same thing except E/Z is more on the newer specifications.
Original post by Gaz94
E/Z isomerism is an example of steroisomerism in the terms of restricted rotation about a double bond. With the requirement for two different groups to be attached to each Carbon of the C=C group.

Cis/Trans isomerism is a special case of E/Z isomerism where two substituent groups are the same.

Whenever there is E/Z isomerism there is Cis/ Trans they are basically the same thing but E/Z is a more modernly used term.


I was told that E/Z is the terminology for IUPAC, and Cis/Trans was just old, i.e. they're interchangeable. :confused:
Reply 10
Avatar for Gaz94
Gaz94
4
Original post by thegodofgod
I was told that E/Z is the terminology for IUPAC, and Cis/Trans was just old, i.e. they're interchangeable. :confused:


I assume so yes. It's in all my OCR Revision guides and i think it's on the specification sheet. Cis/ Trans is old terminology yes. But E/Z is more of what they are getting towards now i think.

Its because compounds like BromoFluoroChloroEthene can't be named with cis/trans

Instead it is named with E/Z

Such as:

Cis but-2-ene is also pronounces E but-2-ene

E/Z isomerism is an example of steroisomerism in the terms of restricted rotation about a double bond. With the requirement for two different groups to be attached to each Carbon of the C=C group.

E/Z Can have different groups. Cis/trans need 2 substituent groups the same.
(edited 12 years ago)
Original post by Gaz94
I assume so yes. It's in all my OCR Revision guides and i think it's on the specification sheet. Cis/ Trans is old terminology yes. But E/Z is more of what they are getting towards now i think.

Such as:

Cis but-2-ene is now E but-2-ene.


Yeah, I get that - I thought you said that there's a difference in the chemistry rather than "Chemistry PCness"
Reply 12
Avatar for Gaz94
Gaz94
4
just edited my post :smile: haha read up :smile:
Original post by Gaz94
just edited my post :smile: haha read up :smile:


ahh - didn't know that :eek: :colondollar:
Original post by thegodofgod
Yeah, I get that - I thought you said that there's a difference in the chemistry rather than "Chemistry PCness"


Yeh not interchangeable I guess..Basically E/z introduced cuz they couldnt name complicated isomers when all group attached to carbons are different!

So what they do is they look for priorities and then change the complicated version of isomer to a simple version like cis/trans (e.g. higher priorities on different side is E) its beyond A-level to actually identify those priorities
Original post by Gaz94
I assume so yes. It's in all my OCR Revision guides and i think it's on the specification sheet. Cis/ Trans is old terminology yes. But E/Z is more of what they are getting towards now i think.

Its because compounds like BromoFluoroChloroEthene can't be named with cis/trans

Instead it is named with E/Z

Such as:

Cis but-2-ene is also pronounces E but-2-ene

E/Z isomerism is an example of steroisomerism in the terms of restricted rotation about a double bond. With the requirement for two different groups to be attached to each Carbon of the C=C group.

E/Z Can have different groups. Cis/trans need 2 substituent groups the same.


I know all of this, but didn't realise that you had word perfectly quoted your specification in your original post in this thread. Therefore, I can only apologise for what may have mislead people.

However, in my specification, it is only required to have an appreciation of the E/Z system but not required to be able to apply anything beyond the cis-trans system as molecules of such complexity won't come up in the exam.
Original post by arvin_infinity
Yeh not interchangeable I guess..Basically E/z introduced cuz they couldnt name complicated isomers when all group attached to carbons are different!

So what they do is they look for priorities and then change the complicated version of isomer to a simple version like cis/trans (e.g. higher priorities on different side is E) its beyond A-level to actually identify those priorities


Not beyond A level. It's in the AQA spec...

3.2.9: Students should:

•

know that the alkenes can exhibit E-Z stereoisomerism

•

be able to draw the structures of E and Z isomers

•

understand that E-Z isomers exist due to restricted rotation about the C=C bond



3.4.4: Students should:

•

know and understand the meaning of the term structural isomerism

•

know that E-Z isomerism and optical isomerism are forms of stereoisomerism

(edited 12 years ago)
Original post by charco
Not beyond A level. It's in the AQA spec...

3.2.9: Students should:

•

know that the alkenes can exhibit E-Z stereoisomerism

•

be able to draw the structures of E and Z isomers

•

understand that E-Z isomers exist due to restricted rotation about the C=C bond



3.4.4: Students should:

•

know and understand the meaning of the term structural isomerism

•

know that E-Z isomerism and optical isomerism are forms of stereoisomerism



My bad I meant to say its not in the OCR spec!
Dont get me wrong here, e/z is in the OCR spec but identifying them NOT in the syllabus
its like if you have C2H2Cl2 you could have CHCl-CHCl or CCl2-CH2 they would be structural isomers
or if you had two molecules both as CHCl-CHCl one could have both Cl on the same side ie: Cl Cl Cl H
C=C OR C=C
H H H Cl

as a result of the double bond the molecules cannot rotate (like Alkanes) so despite having the same structural formula they have a different arrangement of atoms in space therefore it is a stereoisomer
Reply 19
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alow
19
Original post by ++ben*19++
its like if you have C2H2Cl2 you could have CHCl-CHCl or CCl2-CH2 they would be structural isomers
or if you had two molecules both as CHCl-CHCl one could have both Cl on the same side ie: Cl Cl Cl H
C=C OR C=C
H H H Cl

as a result of the double bond the molecules cannot rotate (like Alkanes) so despite having the same structural formula they have a different arrangement of atoms in space therefore it is a stereoisomer


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