How is the length of a particle in a box polyene determined?

[Chemist20]

hello there,

i've read in several places the following: if you have a polyene with J double bonds, and taking into account that the average C-C length is aprox 140 pm, then the length of the box is:

L=2J*140

And I don't get why 2? the number of bonds is not 2J, but 2J-1, for cases such as hexatriene"!


HEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEELP!

thanks :)

 

[sweet springs]

Hi. http://homepages.gac.edu/~anienow/CHE-372/Labs/Conjugated Dyes.pdf may be helpful.


Regards.

 

[Chemist20]

Hi. http://homepages.gac.edu/~anienow/CHE-372/Labs/Conjugated Dyes.pdf may be helpful.


Regards.

thanks, but there it just tells you to do number of carbons times length of bond. which makes sense. I want to be able to related the length of the box to the number of double bonds in the polyene

 

[sweet springs]

Hi. The lines between fomula (4) and (5) may be the answer to your question. Square of number of bonds are corresponding to energy. Regards.

 

[Chemist20]

Hi. The lines between fomula (4) and (5) may be the answer to your question. Regards.

uhhhm thanks but i don't really see what that has to do with the lenght...

 

[sweet springs]

Hi. http://phys-chem.com/pdf/CPL.pdf gives you more detailed explanation. All the pai electrons freely move along the axis of the molecule from one end to the other. They occupy states from the lowest i.e. zero node to higher ones i.e. 1,2 ,3 nodes. Regards.