Chemists everywhere were horrified by a 2019 report that palladium absorbs into stir bars and catalyzes “metal-free” cross-couplings. For 10 points each:
[10e] The best way to avoid such “phantom reactivity” is to soak the stir bar in this mixture of nitric and hydrochloric acids, under the assumption that if this mixture can dissolve gold, it ought to be good enough to clean a stir bar.
ANSWER: aqua regia
[10h] The paper also raised fears of metals contaminating these hard-to-clean discs of porous sintered glass, which are used in spargers (“SPAR-jurs”) and vacuum filters to separate solids.
ANSWER: frits [or fritted glass; accept fritted funnels]
[10m] Contamination is gratifyingly obvious in this reaction, since its radical electride intermediate degrades Teflon and turns stir bars black. This reaction is run at negative 78 degrees Celsius and forms cyclohexadienes.
ANSWER: Birch reduction [or Birch–Benkeser reaction]
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