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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Dolphinsiu on January 18, 2007, 07:00:10 AM

Title: Difference between conformational isomers and configurational isomers
Post by: Dolphinsiu on January 18, 2007, 07:00:10 AM

Conformational isomer and configurational isomers are both involved in rotation! What are their actual difference?(Please take CH3CClFBr as an example!)

As my lecture does not says it in detail, so I get stucked!

Thank you!

Title: Re: Difference between conformational isomers and configurational isomers
Post by: Dan on January 18, 2007, 09:23:43 AM

http://www.chem.qmul.ac.uk/iupac/stereo/BC.html#32

hope that helps

Title: Re: Difference between conformational isomers and configurational isomers
Post by: english on January 18, 2007, 02:29:00 PM

A conformation is just the result of relative group rotation at a given temperature, within the same molecule.  With configurations, you're referring to where one group is relative to another, but one isomer is not the same compound as the other.

Both share the similarity of having relative positions of groups, but the difference is that configurations are obtained by restricted rotations, forming two completely different compounds.  They are not readily interconvertible.  For example, CH₃CH=CHCH₃.  This molecule can exist as cis and trans isomers.  The cis isomer is a different compound than the trans isomer.  To get from one to the other, the molecule has to have sufficient energy to break the pi bond and rotate.

Now consider CH₃CH₃.  Both the conformations shown below are different spatial alignments of the hydrogens, but both of the conformations are still ethane:
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi129.photobucket.com%2Falbums%2Fp229%2Ftriphenylmethyl_chloride%2Fsyn.gif&hash=8eeb09be855d80f90f425a33962f6acdbab8333a)

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi129.photobucket.com%2Falbums%2Fp229%2Ftriphenylmethyl_chloride%2Fgauche.gif&hash=e5e36fd88c20f0b14b5e88faf5b37cddf0ef49b5)