I know that during the development process the developing agents reduce exposed Ag ions to silver. But what happens to Metol which is one of the developing agents?

  • 1
    $\begingroup$ "Quick questions" without elaboration effort are not very welcome, and may be closed. Always think about and search for possible answers thoroughly before posting a question. Chemistry SE site expects to explicitly elaborate the question by at least basic textbook/online search, writing down what was found/understood/tried/failed. $\endgroup$
    – Poutnik
    Nov 3, 2020 at 4:51
  • $\begingroup$ ^Wrong duplicate. Correct duplicate; chemistry.stackexchange.com/q/14680/23561 $\endgroup$
    – A.K.
    Nov 3, 2020 at 12:37
  • $\begingroup$ @Poutnik the problem is that I have contacted three different chemistry teachers, searched throughout the internet, and I was not able to find how Metol (developer D-72) reacts during the developing process of resin-coated paper? $\endgroup$
    – Megija
    Nov 5, 2020 at 7:01
  • $\begingroup$ @Megija The problem with short questions is that respondents can just guess what you did or did not do and can make unnecessarily wrong assumptions. The best approach is to write elaborated question with listing of what you tried and failed and also the question background. I am not an organic chemist, so I would be guessing by guts or search as well as you. $\endgroup$
    – Poutnik
    Nov 5, 2020 at 7:11
  • 1
    $\begingroup$ @A.K. It is unclear if the linked Q/A consider specifically metol oxidation reactions, unless it is deeply in the 2nd level links. $\endgroup$
    – Poutnik
    Nov 5, 2020 at 7:14

1 Answer 1


The analogous B/W developer agent p-hydroquinone is oxidised by silver ions in alkaline environment to p-benzoquinone:

$$\ce{O^{-}-C6H4-O- + 2 Ag+ -> O=C6H4=O + 2 Ag }$$

The related molecule 4-aminophenol ( contained in the Agfa developer Rodinal ) reportedly according to pubs.rsc.org oxidates to NN′-bis-(p-hydroxyphenyl)-2-hydroxy-5-amino-1,4-benzoquinone di-imine, but the analogical structure is not possible for N-methyl-4-aminophenol as the methyl derivate.

Benzoquinone imines. Part 16. Oxidation of p-aminophenol in aqueous solution, Keith C. Brown and John F. Corbett

Abstract: Oxidation of p-aminophenol gives NN′-bis-(p-hydroxyphenyl)-2-hydroxy-5-amino-1,4-benzoquinone di-imine. Data from reactions using potassium ferricyanide as oxidant indicate that this product is formed from 3 molecules of p-aminophenol and that rate-controlling steps depend on solution pH. Thus, rate-controlling steps are coupling of protonated monoimine and neutral p-aminophenol at pH <8, coupling of protonated monoimine and p-aminophenolate at pH 8–10, and above pH 10, coupling of neutral monoimine and p-aminophenolate. The resulting aminohydroxydiphenylamine is rapidly attacked at C-4 by a second molecule of monoimine to give the reduced form of the above di-imine, to which it is then oxidized by a third molecule of monoimine.

with the structural formula NN′-bis-(p-hydroxyphenyl)-2-hydroxy-5-amino-1,4-benzoquinone di-imine* structural formula from chemsrc.com.

  • $\begingroup$ It think it's wrong even for aminophenol AFAIK it makes azo or azoxyphenol when oxidised. $\endgroup$
    – Mithoron
    Nov 4, 2020 at 16:26
  • $\begingroup$ I suppose you are right. Indophenols are blue dyes. $\endgroup$
    – Poutnik
    Nov 4, 2020 at 18:59

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