Wednesday, August 31, 2011

Process Wednesday: Murphy's law

This is how I've always pictured Murphy.
Photo credit: badmovies.org
From our mentor-by-literature Neal Anderson, a comment about the pitfalls of scaleup and workups:
TIP: According to Murphy's Law, whatever can go wrong, will. Plan scale-up operations as though Murphy's Law is true. [snip] 
Close attention must be paid to heterogeneous conditions that occur during during workup and isolation. Thorough extraction of by-products from rich phase into a second phase may not occur if agitation is poor. Residues left in a kettle from a prior extraction, e.g., saturated brine drained away from a rich extract, may contaminate the product. An insufficient settling time may lead to an incomplete phase split, and impurities carried over in the emulsion may contaminate the product. An aqueous wash could be hung up in an invisible spot (e.g. a dip leg or a hose that was not flushed properly) and contaminate the rich extract. Uneven application of cake washes can lead to inhomogeneous product. Uneven heating during drying can lead to localized decomposition. 
I shudder at the possibilities of things that can go wrong during workup, isolation and drying*. It's not real reality until the HPLC comes back clean after the very, very, very last step and the FedEx van is pulling away.

*I once saw a Murphy-possessed drying oven go haywire (even though it was off) and shoot the temperature way past the m.p. of final compound. Not a good feeling at all to come back to a funny smell and brown goo.

1 comment:

  1. Ah Leprechaun, one of Jennifer Aniston's best roles, IMHO. Right up there with Courtney Cox in Master of the Universe with Dolph Lundgren (who incidentally has a BS and MS in chemical engineering).

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