What's that Crud in My NMR Sample?

Scene:

The reaction finished in 20 minutes by TLC. You grabbed a quick aliquot for LCMS; one peak! Quickly, you quenched, extracted, perhaps pushed through a silica plug for good measure. After concentration, a gorgeous white powder formed, so you pulled high vac for 20 minutes and rushed down to "get your proton on." But, darn it! Still wet with traces of, well, something...

Friends, has this ever happened to you? Trace impurities in otherwise perfect spectra lead to much head-scratching and SI docs labeled "final product_spectrum 5." 

The three papers linked to this post should help.

• Nudelman, Gottlieb, Kotlyar - 1997. The one that started it all.

• Fulmer, Miller, Sherdan, Gottlieb, Nudelman, Stoltz, Bercaw, Goldberg. Updated for 2010, with an organometallics bent. Now includes gases!

• Babij, McCusker, Whiteker, Canturk, Choi, Creemer, DeAmicis, Hewlett, Johnson, Knobelsdorf, Li, Lorsbach, Nugent, Ryan, Smith, Yang, 2016. The new kids on the block: greener solvents for process chemistry and scale-up. *Update (23 Feb) - A kind commenter points out that #3 is free to download under the ACS AuthorChoice program. Sweet!

The new chart offers recommendations (colored arrows) based on Chem21 assessments of environmental impact, safety, and toxicity. Shown above are chemical shift tables (1H) in deuterated chloroform, acetone, and dimethyl sulfoxide.

If I were joining a synthetic lab this year, or starting an internship / work-study, I'd download 'em all and thumbtack liberally to the back of my bench. Guaranteed utility.