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  1. #1

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    Dimezone-S oxidation products

    Attached is a summary of some experimental results which puzzle me regarding Phenidone (in the case the Dimezone-S derivative) oxidation products, pH and sulfite.

    I don't know how many Dimezone-S oxidation products there are, but we know at least one of them is coloured. If we assume the concentration of this oxidation product is directly related to the depth/chroma of the solution colour, I'm surprised by some of my observations:

    1. Sulfite appears to partially decolourize the solution. According to Haist, with benzene-derived developing agents, sulfonation of oxidation products by sulfite apparently explains the decolourizing action. But sulfite is not supposed to for sulfonates with Phenidone oxidation products.

    2. Bisulfite appears to have the same effect on colour as sulfite. I tested this by first lowering the pH of the sulfite-free solution to ~4 using acetic acid, which lightened the solution colour significantly, and then adding sodium bisulfite/metabisulfite, which further lightened the colour to that observed for an alkaline sodium sulfite-Dimezone-S solution.

    3. Reducing the pH of the sulfite-free solution to a neutral state also appears to have a decolourizing effect, though to a slightly lesser degree than the addition of sulfite. On the other hand I suppose it is possible this effect is the result of some reaction between the Dimezone-S oxidation product and acetic acid, rather than the pH change per se.
    Attached Files
    Last edited by Michael R 1974; 07-12-2015 at 08:58 PM. Click to view previous post history.

  2. #2
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    Michael, Phenidone is a Hydrazine derivative. As such it and its oxidation products undergo (or should undergo) any reaction related to HQ. The basic reaction is ring opening. There are many others as the ring opened compound then can undergo a series of reactions that result in a witch's brew of organic compounds.

    PE

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    Besides the familiar magenta product IIRC there is also a red product owing its vivid color to the fact that it is a free radicle. There is also a blue product. The oxidation of phenidone is complex and some of the oxidation products are hard to reproduce. When I was in college I attempted to measure the amount of phenidone in a developing solution. The developing agent was extracted using chloroform. The chloroform solution was then placed in a UV spectrometer to measure its concentration. Unfortunately the UV light caused the phenidone to decompose. You could actually see the path of the UV beam through the cuvette as a smoky trail.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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    Ron, Gerald, thanks for the feedback. I suspected it was more complex than I was making it out to be which would explain why I got complex results!

    Even the visual solution colour is tricky to describe. Depending on the viewing angle the colour is difficult to pin down. Looking down through the top of the beaker the colour tends toward the magenta (which in the dark coloured cases looks like a deep beet colour) while looking through the side or from a distance, it looks orange (all the way to deep orange/brown in the dark coloured cases).

    Apologies for the multiple typos in my original post.

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    My post above is incorrect!

    Here is a corrected copy with apologies.

    Phenidone is a Hydrazine derivative. As such it and its oxidation products DO NOT undergo (or should NOT undergo) any reaction related to HQ. The basic reaction is ring opening. There are many others as the ring opened compound then can undergo a series of reactions that result in a witch's brew of organic compounds.

    The changes are all in caps. Yes, phenidone is much more complicated when it oxidizes than HQ and they are totally dissimilar. I did a lot of research on hydrazines and their derivatives and got a lot of products from their oxidation.

    PE

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    Thanks for the correction. Makes more sense to me now. Still complex indeed, but interesting nonetheless.

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    Quote Originally Posted by Gerald C Koch View Post
    Besides the familiar magenta product IIRC there is also a red product owing its vivid color to the fact that it is a free radicle. There is also a blue product. The oxidation of phenidone is complex and some of the oxidation products are hard to reproduce. When I was in college I attempted to measure the amount of phenidone in a developing solution. The developing agent was extracted using chloroform. The chloroform solution was then placed in a UV spectrometer to measure its concentration. Unfortunately the UV light caused the phenidone to decompose. You could actually see the path of the UV beam through the cuvette as a smoky trail.
    I was thinking of trying that lately, but with already oxidized developer. I wonder if anyone has ran an old developer through a LCMS with UV PDA. That is a capillary liquid chromotography unit with photo diode array for measuring the UV spectrum after the separation column, which then feeds an electrospray source mass spectrometer. It seems like you could analyze everything that way.

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    IR and NMR both give better resolution and you can do a time study due to the speed of measurement.

    PE

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    Obviously once the phenidone ring ruptures the phenidone can no longer be reconstituted by reduction. IIRC this point of no return is reached even earlier in the oxidation process. (I'm not able to get to my copy of Mason.) But these latter oxidation products are of academic but not practical interest.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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    Quote Originally Posted by Photo Engineer View Post
    IR and NMR both give better resolution and you can do a time study due to the speed of measurement.

    PE
    I agree the IR would give better resolution and be good for determining ratios of oxidation products after extracting with a non-aqueous solvent. The NMR isn't very good for quantitative analysis I don't think, and it is finicky and the developer would have to be made with deuterated water. Not sure if it would tolerate the salts in a regular developer solution. The PDA UV would be only useful to give an indication when a substance is eluting from the column but the MS would give enough data to figure out the compound and amounts perhaps even for the salts. From what I'm reading, phenidone has pretty stable oxidation products until it is oxidized by oxygen for a long time with the absence of sulphite in which case you have the nitrogen ring opening but the compounds would still be identifiable, and not as complicated as the ascorbic acid case. Of course maybe there are more surprises if it gets hit by enough UV from what Gerald says.

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