[czeslaw]

Hi,
I have a task:

Starting from (E)-1,2-dimethylcyclopentane, obtain (Z)-1,2-dimethylcyclopentane. How to reverse compound configuration?

Thanks for the answers.

[zsinger]

We don't give away answers here .  Well certainly help you though. 

What must first happen at the stereo-centers in order for a change in chirality?
                              Zack

[AlphaScent]

You are trying to write (E)-1,2-dimethylcyclopentENE

E and Z do not denote chirality!!! 

It is the Cahn-Ingold-Prelog nomenclature for stereochemistry of olefins.


http://en.wikipedia.org/wiki/E-Z_notation

[AlphaScent]

How many isomers are possible for 1,2-dimethylcyclopentene?

[sjb]

You are trying to write (E)-1,2-dimethylcyclopentENE

E and Z do not denote chirality!!! 

It is the Cahn-Ingold-Prelog nomenclature for stereochemistry of olefins.


http://en.wikipedia.org/wiki/E-Z_notation

Not just olefins, but anywhere rotation is restricted, so perfectly OK in this instance.

[Dan]

You are trying to write (E)-1,2-dimethylcyclopentENE

E and Z do not denote chirality!!! 

It is the Cahn-Ingold-Prelog nomenclature for stereochemistry of olefins.


http://en.wikipedia.org/wiki/E-Z_notation

Not just olefins, but anywhere rotation is restricted, so perfectly OK in this instance.

IUPAC seem to say that E/Z should not be used for ring substituent relative configuration (you should use cis/trans).

See http://www.chem.qmul.ac.uk/iupac/stereo/DE.html#17

E-Cyclopentene doesn't exist, so I assume the question is about cis- and trans-1,2-dimethylcyclopentane? Tricky one.

[sjb]

Ahh, hadn't realised that, but can't see why the issue that arises for e.g 3-methylpent-2-ene does not also raise its head for 1,2-dimethyl-1-ethylcyclopentane. Thanks for the link - been a while since I needed to look into this closely