Bond-Lengths?

[Maqboole]

Hi,

 

I was wondering how you calculate bond lengths of HCl? Infra-red spec is an option which uses the mechanism of vibration to determine the functional groups. I want to know would this technique aslo be used to find the bond length of HCl? If so then should not HCl be in Gaseous state?

 

Thank You

[Testo]

Well an IR absorption spectrum would be capable of detecting the transistions from the ground state to the first excited state and assuming the rigid-rotor (for roational spectra) model you can calculate the bond length from the transistions. And yeah it will have to be in the gas phase and free of other gases of course =)

[John Cuthber]

You can get the data from the fine structure of an IR spectrum, but the easy way is to look at the microwave spectrum. That gives you the rotational frequencies. Given the masses of H and Cl you can work out what bond length corresponds to the right moment of inertia for the measured frequencies.

Another way, more useful for solids is to look at the Xray diffraction patern. You can do similar electron diffraction measurements on vapours.

[ChemSiddiqui]

Yeh I think the rotation spectra would do the trick as Testo mentiones. John's suggestion is aslo good one as well.