Ax165Xj
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PABA (para-aminobenzoic acid)
Short and sweet: I have some PABA and have no use for it. Does anyone know of any particularly interesting things I could do with it?
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DraconicAcid
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It forms an insoluble precipitate with copper, and can be used for gravimetric analysis.
Adjust the pH of the solution (containing 20-100 mg copper) to 4-4.6 using 20 mL of 0.2 M acetic acd/acetate buffer in a beaker. Heat the solution to
boiling, add 30 mL of PABA solution (1.6% w/v PABA dissolved in 0.1 M sodium hydroxide) dropwise with constant stirring, and allow to stand on the
steam bath for 2-3 hours (or at RT overnight). Let the solution cool, filter off the precipitate, wash with water and dry at 80-100 oC for 90
minutes.
(That's the instructions for quant analysis from Talanta, 1968, Vol. 15, p 149 (Erdey, L., Marik-Korda, P., Liptay, G.) If you just want to make the
compound, you wouldn't have to let it sit so long, or dry so assiduously. The buffer is needed to prevent coprecipitation of copper(II) hydroxide
(happens about pH 6). Similar conditions will also precipitate compounds with silver, mercury(II), lead, aluminum, iron(II), bismuth, antimony(III),
and tin(II), but zinc, cobalt(II) nickel and cadmium will only precipitate at higher pH values.)
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Metacelsus
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Make benzocaine!
https://en.wikipedia.org/wiki/Benzocaine
(Esterify with ethanol and acid catalyst.)
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jwpa17
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Once you make the benzocaine, you can use it to derivatize (some) sugars via a reductive amidation. It does require sodium cyanoborohydride,
methanol, and glacial acetic acid, all of which are commercially available. Makes a fluorescent derivative.
I seem to recall that you can derivatize reducing sugars with PABA itself, but I've never done that.
Ought to be able to do reductive amidation of most any aldehyde, actually.
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HeYBrO
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Science madness user nb198 posted an excellent video on the synthesis of PABA; https://www.youtube.com/watch?v=ZMxT8ra1hwk.
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Nicodem
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Thread Moved
3-4-2014 at 05:39 |
Mychemlife
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Video is no longer available.
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Corrosive Joeseph
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The easiest route to PABA is definitely this one....... $23 for 500 grams and $34 a kilo
https://www.bulksupplements.com/para-aminobenzoic-acid-paba....
/CJ
Being well adjusted to a sick society is no measure of one's mental health
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