Dear Chandrashekar,

I am a medical Doctor and not an expert in this field. But your question was interesting and I am attempting to answer the same.

Force constant of a bond is a reflection of its bond strength. It takes more strength to stretch a bond and break it than to bend it. Lots of paper out there that have calculated force constants of a bond between 2 atoms.

In a molecule has n bonds, then most papers seem to say that the total force constant is not simple addition of each of the bonds. There is some variation on which many people have made models.

So, the answer to your question might be this. Yes, you can figure out the force constant for a molecule if you know the force constant for each individual bond. Simple addition might give you a rough idea but you will need a bit more complex modeling than just addition.

I am attaching a couple of references

a. D.Michael Byler, Heino Susi, William C. Damert. Relation between force constant and bond length for carbon—nitrogen bonds. Spectrochimica Acta Part A: Molecular Spectroscopy Volume 43, Issue 6, 1987, Pages 861–863

b. attached as an article

Hope it has helped in some way.

regards

It makes no sense to speak of the force constant for an entire molecule as a single scalar quantity. Rather it will be a matrix of quantities depending on the molecular geometry and number of bonds. See the attached lecture series  on modelling systems of springs.In simple linear series and parallel spring systems you can calculate overall constants but not generally.