Chemists: How accurate is melting point data?

[beer]

Let's say someone gave you a few hundred mg of a powder. It was a moderately complex synthesis, but nothing overly complicated for third year chem majors. Assume it was an organic synthesis, say, something like, oh, MDMA.

The only confirmation you have been provided was melting point data. How confident can you *really* that the product was really the desired product and not an intermediate?

Short of GC/MS or NMR....is there a better way to test the product yield?

And note that this is not for my own experience. I am just trying to formulate an argument to someone that says homemade drugs are safer because you know the product. Stupid chem majors

 

[Heisenberg]

I'm not a chemist (I'm physics) but I would say that the melting point data is accurate to at least 2 or 3 significant figures. The major source of error would be with the technique itself and being sure that the reactant was uniformly heated to the melting point.

 

[fatalbert]

well, it is as accurate as your technique. In some peoples hands it could give 4 sig figs in others less. However, it alone doesn't prove what you have made. Because there are many substances and some have very close melting points which make it hard to tell. Therefore, unless you have already used a procedure before and know that it makes the correct product, you wouldn't use it to identify the product alone. Instead you would use it as one piece of evidence. An NMR and IR spectra would also be necessary for an organic synthesis. However, the melting point could be used to test purity. Because if the substance has contaminants, and you know what the melting point should be, you can check for variances to make sure you have what you think you have. This is a quick test. That way if the results say there is something else in there too, you can find out what that is using the more sophisticated methods like NMR and IR

 

[ElFenix]

why are you melting X?

 

[beer]

Originally posted by: ElFenix
why are you melting X?

I am not. I have absolutely no background in general chemistry, much less organic or any lab experience. So when I have chem majors talking to me I don't know what they're saying to me is true or BS.

 

[zephyrprime]

Melting point data should be very accurate. But there are things that can affect melting point like atmospheric pressure. Also, some reactions retain a significant amount of the original reactants in them even after reacting.