Molecule of the Day

Yesterday, I mentioned naphthoresorcinol as a reagent for aldehyde testing. Did you know: at one point during the Cold War, the Soviets used to put a certain aldehyde on American operatives in the USSR as a tracer?


That aldehyde, NPPD, caused a kerfuffle in the 80’s. There was outrage that Americans were being “tagged,” and speculation as to whether it might be dangerous. Some analytical chemists leaned back, scratched their beards, and said “sounds kind of neat.” And even recently, the compound was re-examined.

Anyone have any NPPD stories?


  1. #1 Sam
    April 9, 2009

    How was this a “tag” of American operatives? It is undoubtedly UV active but how would that be helpful? It could definitely be toxic – nitro group & multiple likely sites of alkylation.

  2. #2 mob
    April 9, 2009

    Love your blog! Sorry, no NPPD stories (That I know of…) BTW, what app do you use to draw your chemical formulae? I just discovered ChemSketch the other day and it seems to work good.

  3. Wow, how interesting. This would make a great science fair project topic. Could molecular tags be effectively developed and traced? And if so, how would it be done?

  4. #4 echogreen
    April 21, 2009

    I was stationed at the American Embassy in Moscow where it was known that NPPD was being used 1986-1987. It was known agents were being exposed to it but as usual the ambassador remained diplomatic in his outrage.

  5. #5 Bob
    July 17, 2009

    I was one of the diplomats at the US Embassy who was tagged with NPPD. My vehicles and residence were tested by the EPA for NPPD in the fall of 1985. Only two years later did I get a letter from the State Department Medical Office confirming that I had indeed been tagged with NPPD, but I was assured that the substance was detected in such a small dosage that it was not considered harmful to my health!

  6. #6 Julian
    May 16, 2010

    I am not a scientist, but literature says that the substance is properly 5-(4-nitrophenyl)-2,4-pentadienal.

  7. #7 Elmer
    February 9, 2011

    I recall that stuff, I ran the toxicology study which we did in house AT NIH. That is some nasty stuff.

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