why the color of Furfural change from colorless to brown directly when exposed to air and then need to distillation to form its Schiff base with an amine which also converts from red to dark directly after complete the reaction
I didn't know that furfural is colourless, but if you say it is, then the brown colour commercial furfural usually has possibly originates from oxidation or condensation products. However, even an intense colour does not mean that the impurity concentration is high. In fact, traces of something can cause intense colours, e.g. ruby is red because of containing 0.1 at% Cr(III), a few mg/L of methyleneblue in water give a deep blue colour. Therefore, the colour is no reliable indicator for quality or purity.
Article The Atmospheric Oxidation Mechanism of Furfural Initiated by...
Dear Abdel-Aziz Abu-Yamin, furfural darkens rather rapidly when exposed to air. To keep it as a colorless liquid, you need to store it under nitrogen after purification by distillation. However, if you want to use it as a starting material for the synthesis of Schiff bases, I assume that some brown coloration doesn't really matter, as the resulting Schiff base product will most likely be purified by recrystallization.
Thank you Dr. Jürgen Wintner and Dr. Frank T. Edelmann . Yes, I condensate it and prepare several Schiff bases. but if I forget it after distillation for 5 -8 min; before reacting it, it directly converts from very pale yellow (or colorless) to dark brown
Thank again
The color of Furfural change from colorless to brown due to air oxidation to acid. The colour of Schiff,s base is also dark brown , this is because of extended conjugation.
Dear Abdel-Aziz Abu-Yamin, I'm surprised to hear that the furfural darkened so rapidly (within minutes). Did the Schiff base preparation work?
Dear Frank T. Edelmann, yes after simple distillation it work good and if you need NMR and mass result I will send it to you. my e-mail is: [email protected]
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