What causes benzaldehyde to turn yellow?
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This post was last edited by Desert Fish on 2015-8-18 09:13. Benzaldehyde oxidizes rapidly into white benzoic acid under light; this reaction does not involve any change in color. So what causes benzaldehyde to turn yellow?
I guess aldehydes can self-polymerize
It’s not just benzoic acid; there are also other gases in the air such as carbon dioxide and so on
There are many reasons for the yellowing of benzaldehyde; in summary, they include the following: 1) During the production of benzaldehyde, small amounts of formaldehyde remain, and these formaldehyde molecules can undergo polycondensation reactions to form polyformaldehyde； 2) The residual formaldehyde is oxidized by oxygen in the air to form more complex alcohols or acids ； 3) There may be metal ions in the production process, such as trivalent iron ions and the like ； 4) The oxidation reaction that occurs in benzaldehyde itself may also cause a change in color. The above four points are what I came up with personally; I hope they can help you!
Benzaldehyde condenses to form benzoin, and the crude form of benzoin is pale yellow in color.
Our company uses a toluene liquid-phase oxidation process to produce benzoic acid, with benzaldehyde as a by-product; benzaldehyde does not contain formaldehyde； If benzaldehyde contains trivalent iron ions, is it the color of the metal itself that causes benzaldehyde to appear yellow, or are other reactions taking place? If the yellow color of benzaldehyde is caused by the color of trivalent iron ions themselves, then what is the minimum concentration of trivalent iron ions in ppm required?
You have thought very comprehensively; I hope you can help me think more deeply about it, as this issue has been bothering me. . .
If it contains iron ions, it will turn yellow after being left alone; this happens even faster in sunlight