[laura.g.berger]

Hello!

Considering this molecule  C-C-O-C-O-C (ommited hydrogen atoms for this example). If i want to calculate her length, i have to consider covalent radius of each atoms or Van der Waals radius or the atomic radius?

Thank you.

[Archer]

I don't recall ever doing this mathematically, I have always used computational chemistry for this purpose.

If it were required then personally I would consider bond lengths and bond angles for this.

However I am not sure if this is the most accurate (or indeed correct) method for calculating the lenght of a molecule.

[Corribus]

If it were required then personally I would consider bond lengths and bond angles for this.

I think this will get in you in the ball park for most standard organic molecules. However for something more accurate I agree, an ab initio calculation will be necessary.

[laura.g.berger]

Could you, please, indicate me a software to do that?
I use Debian and Windows in my computer.

[Archer]

For very basic size determination you can use ACD chemsketch (freeware).

It has a 3D viewer which will give simple distance measurements.