[Rutherford]

Here is the problem: http://ecareerpoint.com/IIT-JEE/Chemistry/Organic_Chemistry_-1/Isomerism/Z-E_Isomers/Z-E%20Isomers/PracticeQuestion.aspx
I see that the double bond on the left side has an E configuration, but the double bond on the right side troubles me. The biggest priority on the right side of that bond has COOH, but what has the biggest priority on the left side, because the left side C atom is attached to a 2 similar C atoms and everything is the same priority if I go along the structure. Then, why the right side double bond has an E configuration, too?

[discodermolide]

Here is the problem: http://ecareerpoint.com/IIT-JEE/Chemistry/Organic_Chemistry_-1/Isomerism/Z-E_Isomers/Z-E%20Isomers/PracticeQuestion.aspx
I see that the double bond on the left side has an E configuration, but the double bond on the right side troubles me. The biggest priority on the right side of that bond has COOH, but what has the biggest priority on the left side, because the left side C atom is attached to a 2 similar C atoms and everything is the same priority if I go along the structure. Then, why the right side double bond has an E configuration, too?

Sorry but I do not see a COOH in any of the molecules.
Use the Cahn-Ingold-Prelog system to obtain the priority.
p.s. I just checked the link again and it produced a different set of molecules than it did the first time I opened it!!

[Rutherford]

Sorry, the questions changed I will try to draw the molecule in chemdraw.

[AWK]

What exactly does mean E and Z prefix?

[Rutherford]

What exactly does mean E and Z prefix?

I know, the questions changed. Here is the molecule I was asking about:



My thoughs are here:

I see that the double bond on the left side has an E configuration, but the double bond on the right side troubles me. The biggest priority on the right side of that bond has COOH, but what has the biggest priority on the left side, because the left side C atom is attached to a 2 similar C atoms and everything is the same priority if I go along the structure. Then, why the right side double bond has an E configuration, too?

[discodermolide]

What exactly does mean E and Z prefix?

I know, the questions changed. Here is the molecule I was asking about: http://imageshack.us/f/209/20771312.gif/
My thoughs are here:

I see that the double bond on the left side has an E configuration, but the double bond on the right side troubles me. The biggest priority on the right side of that bond has COOH, but what has the biggest priority on the left side, because the left side C atom is attached to a 2 similar C atoms and everything is the same priority if I go along the structure. Then, why the right side double bond has an E configuration, too?

Starting at the double bond attached to the ring, going down you have CH2-CH-C-CN, going up you have CH2-CH2-CH-C-CN.
The former has the higher priority therefore the right hand double bond is E.
I hope you can follow that if not I'll draw it out.

[Rutherford]

Thanks, I understood, but if there was a four-sided cyclyc figure instead of the five-sided figure then everything would be same. How to determine if that is Z or E?

[discodermolide]

Thanks, I understood, but if there was a four-sided cyclyc figure instead of the five-sided figure then everything would be same. How to determine if that is Z or E?

Not sure, but I think both double bonds are E.
I drew it and here is the name:
(E)-2-(3-(3-amino-1,2-dicyanoprop-1-en-1-yl)cyclobutylidene)-3-hydroxypropanoic acid

[AWK]

Exactly as in:
H2C=C(CH2OH)COOH or in CH2=CH2 - geometric isomer cannot be determined

[Rutherford]

Thanks, just one last question: What would be the complete name of the following compound http://imageshack.us/photo/my-images/585/95531458.gif/ using the Z-E system? I see that it is the Z configuration, but how to continue the namming with the groups attached to the C atoms. Is it Z-1-bromo-1-fluoro-2-chloro-ethene?

[AWK]

You name shows lowest locants - OK

[Rutherford]

I didn't understand what you said. You mean that Z-1-bromo-1-fluoro-2-chloro-ethene is ok?

[Dan]

The  IUPAC name would be (Z)-1-bromo-2-chloro-1-fluoroethene. Note differences compared to yours (hyphenation, parentheses, substituents in alphabetical order)

The comment regarding the locants refers to why it is not called (Z)-2-bromo-1-chloro-2-fluoroethene. The names describe exactly the same structure, but we choose the name in which the locant numbers are lower.

[Rutherford]

Ok, thanks.