Electrochemical coupling of two phenols which differ in their oxidation potential

1. An electrochemical process for preparing a biphenol, the electrochemical process comprising:

preparing a reaction solution by introducing a solvent or solvent mixture, a conductive salt, a first phenol having an oxidation potential |E Ox 1|, a second phenol having an oxidation potential |E Ox 2| into a reaction vessel, where: |E Ox 2|>|E Ox 1| and |E Ox 2|−|E Ox 1|=|ΔE|, the second phenol being added in excess relative to the first phenol, and the solvent or solvent mixture being selected such that |ΔE| ranges from 10 mV to 450 mV, wherein the reaction solution is free of a fluorinated compound and transition metals,

introducing two electrodes into the reaction solution,

applying a voltage to the electrodes, and

coupling the first phenol to the second phenol to produce the biphenol.

2. The electrochemical process according to claim 1 ,

wherein the second phenol is used at least in twice the amount relative to the first phenol.

3. The electrochemical process according to claim 1 ,

wherein a ratio of the first phenol to the second phenol ranges from 1:2 to 1:4.

4. The electrochemical process according to claim 1 ,

wherein either the first phenol or the second phenol has an —O-alkyl group.

5. The electrochemical process according to claim 1 ,

wherein the solvent or solvent mixture is selected such that |ΔE| ranges from 20 mV to 400 mV.

6. The electrochemical process according to claim 1 ,

wherein the reaction solution does not comprise an organic oxidizing agent.

7. The electrochemical process according to claim 1 ,

wherein the first phenol and the second phenol are selected from the group consisting of Ia, Ib, IIa, IIb, IIIa and IIIb:

where R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 10 , R 11 , R 12 , R 13 , R 14 , R 16 , R 18 , R 19 , R 20 , R 21 and R 24 are selected from the group consisting of —H, -alkyl and —O-alkyl;

R 8 , R 15 and R 17 are -alkyl;

R 1 , R 9 , R 22 and R 23 are selected from the group consisting of —H and -alkyl, and

the first phenol is combined with the second phenol as follows:

the first phenol is Ia and the second phenol is Ib;

the first phenol is Ib and the second phenol is Ia;

the first phenol is IIa and the second phenol is IIb;

the first phenol is IIb and the second phenol is IIa;

the first phenol is IIIa and the second phenol is IIIb;

the first phenol is IIIb and the second phenol is IIIa.

8. The electrochemical process according to claim 7 ,

wherein either the first phenol or the second phenol is Ib, and R 1 and R 2 are not both —H with the proviso that R 3 is methyl.