Albert Matlack, one of the founding educators of green chemistry and author of the book ‘Introduction to Green Chemistry’, selects his favourite papers in Green Chemistry this month…
Olefin metathesis in aqueous media, Jasmine Tomasek and Jürgen Schatz, Green Chem., 2013, 15, 2317–2338, DOI: 10.1039/C3GC41042K
This should cause one to think about how many discoveries leading to this result were made by chance. Herbert Eleuterio of duPont discovered metathesis when he used a molybdenum catalyst in a Ziegler polymerization of ethylene in 1957. Efforts to get consistent results with tungsten hexachloride were futile until it was found that tungstenoxytetrachloride worked well. Most metathesis catalysts were sensitive to air and moisture. However, a run with a hydrated ruthenium salt worked just as well as the anhydrous compound. This review covers work since then. The field of polymers today arose from accidental discoveries.
Low density polyethylene was found when chemists at ICI tried to react benzaldehyde with ethylene and got a trace of air in the bomb. High density polyethylene was discovered by Karl Ziegler who was studying the oligerimerization of ethylene with triethylaluminum when a trace of nickel from a partially cleaned bomb gave only 1-butene. When he tried titanium tetrachloride HDPE formed. Natta discovered stereoselective polymerization when he extended the reaction to propylene. Metallocene catalysts for the polymerization of olefins by Kaminsky were discovered when a student failed to blanket a polymerization with nitrogen. Plunkett of duPont discovered poly(tetrafluoroethylene) when a cylinder known to be full of the monomer released no monomer. Conducting polymers were found by Shirakawa, MacDiarmid and Heeger when a student put 1000 times too much catalyst in a polymerization of acetylene. An iodine reaction, presumably to determine the content of double bonds, showed how to dope it.
Add to these results of serendipity, H.C. Brown’s discovery of hydroboration while trying to reduce a double bond with diborane. Notice the number of Nobel prizes awarded for the various discoveries.
The message is, if something unusual happens, check to see why.
Organic solvent-free and efficient manufacture of functionalized cellulose nanocrystals via one-pot tandem reactions, Lirong Tang, Biao Huang, Nating Yang, Tao Li, Qilin Lu, Wenyi Lin and Xuerong Chen, Green Chem., 2013, 15, 2369–2373, DOI: 10.1039/C3GC40965A
Functionalized cellulose nanocrystals were formed via ball milling followed by ultrasonication. The reaction was run with a large excess of maleic anhydride in 20% aqueous sulfuric acid. No organic solvent was present. After balling for an hour, ultrasonication for 7 hours gave a 61% yield with 0.34 degree of substitution. It might be good to substitute less maleic acid and to run a final ring closure by heating. Other monomers could be tried as well.
