[alexalexmaiden]

Hello , i would like to ask you something that  i cant find the answer ...so  the bond between 15-15' carbons of b carotene is cis or trans ? and why ? thank you very much (sorry for writting in this subject)

{MOD Edit -- split off topic and write topic title}

[Dan]

What is the definition of cis/trans?

[alexalexmaiden]

ex.> 1,2-dichloroethene  ... In one, the two chlorine atoms are locked on opposite sides of the double bond. This is known as the trans isomer. (trans : from latin meaning "across" - as in transatlantic).

In the other, the two chlorine atoms are locked on the same side of the double bond. This is know as the cis isomer. (cis : from latin meaning "on this side")

[Dan]

OK, so how does that apply to β-carotene?

[alexalexmaiden]

i dont know ... it is a question from past papers (am from greece btw) do you  think it is wrong question ?  (basically in the question it says for the geometry of the double bond)

[Babcock_Hall]

We like to help students think things through for themselves.  Which do think it is, and why?  BTW, I am half-Greek and was just listening to something by Manos Hadjidakis.

[alexalexmaiden]

oh thats cool (γειά σας ). I think it is trans because the substitutes are locked on opposite sides of the double bond ...

[Babcock_Hall]

Yes, it is trans in configuration.  You might find the following reference to be of passing interest:  http://www.ncbi.nlm.nih.gov/pubmed/14934252