A Conversation for Alkenes
Isomers
Orcus Started conversation Aug 27, 2003
It would have been nice to see some mention of E and Z isomerism here.
Everything else is there for your basic A level course though I would guess 
Excuse me for going round criticising all your articles 
Isomers
Rho Posted Aug 27, 2003
>Excuse me for going round criticising all your articles
You're excused!
RhoMuNuQ
Isomers
Special Agent Poops Posted Sep 4, 2003
Is E and Z isomerism the same as cis and trans? Am I really that old at 21 that they've already changed the names of everything AGAIN? Oh no!
Isomers
Orcus Posted Sep 4, 2003
Yes.
E and Z are the same as R and S for chiral centres (that is the groups around the stereocentre are assigned priorities by the Cahn-Ingold-Prelog rules).
Basically cis and trans can be conusing whereas the rules for E and Z are laid in stone and are unshakeable. Ie. E and Z are absolute stereochemical configurations.
E = trans, Z = cis generally speaking.
Isomers
EwenMc Posted Sep 8, 2003
cis and trans are not confusing *if* the terms are limited to C=C-bonds with a hydrogen on each carbon. BTW, I can't think of any A-level (or IB) which includes E-Z or R-S notation.
Isomers
Orcus Posted Sep 9, 2003
You won't find one, they only introduce it at degree level 
Ever seen the article here on h2g2 about lies, damn lies and science lessons?
You are quite correct, it's not confusing at all when there is only one substituent at either end of the double bond. Unfortunately this cannot be deemed as reality as there are often more than one at either end and then the cis or trans notation becomes *highly* subjective and is no longer sufficient.
Isomers
BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows Posted Dec 26, 2008
The Salters A Level syllabus contains E and Z nomenclature from this year.
Regarding Orcus' observation earlier that yjis Entry 'probably contains all that one needs at A Level' it doesn't. It is severely limited. For example, it doesn't explain what sort of substances add across double bonds.
I've been thinking of updating it for some time.
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Isomers
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