Which type of spectroscopy is more powerful?

3 Answers
Oct 4, 2015

Every spectroscopy is powerful according to your needs.


The most powerful spectroscopy that can give you a great idea about the structure of organic molecules is NMR.

However, NMR is not enough sometimes; therefore, you will need to use Mass Spectrometry. Moreover, mass spectrometry might not help you enough, then you have to use elemental analysis, and so on.

To my opinion, every spectroscopy is powerful according to your needs.

Oct 4, 2015

Older chemists might tell you about sporting and non-sporting methods of analysis.


When you go duck shooting (so I am told), it is considered very unsporting to shoot a sitting bird, and it is only sporting to shoot at a bird on the wing. Both X-ray crystallography, and NMR spectroscopy are definitely non-sporting means of analysis, i.e. direct methods of analysis. Of course, you sometimes cannot get suitable crystals for an X-ray experiment, and NMR spectroscopy cannot be performed on paramagnetic materials.

Nevertheless, as has already been mentioned, analysis comprises a suite of techniques. Combustion and gravimetric analysis, things that chemists could do 100 years ago, are still used today. Even with a crystal structure, elemental analysis is still a requirement, and no reviewer would accept claims of a new compound without verifiable details of the percentage of elements within a sample.

There is also a question as to whether the solid state structure (the structure that may be revealed from a X-ray crystal structure experiment) is the same as the structure in solution. They are not necessarily the same, and a structure might be an aggregate in the solid state and a single entity in solution. Good chemists take pains to investigate the matter.

Oct 4, 2015

It depends on your intention. Each one is suited for particular purposes, and each one falls short in some aspects. If there were one "best" one, we probably wouldn't have as many spectroscopic techniques as we do today.

If you want to identify organic compounds, Nuclear Magnetic Resonance (NMR) Spectroscopy tends to be a good choice, whether it is #""^1 "H"# NMR or #""^13 "C"# NMR.

An alternative and cheaper way (roughly 10x cheaper) is to use Infrared Spectroscopy, whether you have an older dispersive model or the faster and more modern Fourier Transform models (FTIR), which allows you to quickly take spectra of said organic molecules to see what functional groups are present. It doesn't tell you the locations of protons or their communicative interactions, but depending on your experiences and comforts, you may find IR easier to work with when identifying functional groups.

If you still aren't sure of the way the organic molecule is put together (maybe it's not known at all), then if you have the resources, Mass Spectroscopy is a good idea so you can study the fragmentation pattern and better figure out what the connectivities are.

For Organic Chemistry, you will use any of these three at some point, so it's good to get to know them.