Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing organic compound
Reexamination Certificate
2002-04-04
2003-12-16
Wong, Edna (Department: 1753)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing organic compound
C205S431000
Reexamination Certificate
active
06663764
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to glycine derivatives, and more particularly to a process for preparing glycine derivatives that are free from organically bonded halogen and/or halide ions. The present invention also relates to the use of such glycine derivatives in cosmetic preparations.
BACKGROUND OF THE INVENTION
Glycine derivatives such as betaines are known as mild and compatible substances which may be typically co-used in large amounts for the preparation of cosmetic preparations for the cleansing and care of skin and hair.
In the prior art, glycine derivatives are typically prepared by reacting tertiary amines with excess monochloroacetic acid in a basic aqueous solution at an elevated temperature.
Great efforts have, in the past, been made to prepare glycine derivatives which are free from impurities which may cause skin irritations or are otherwise undesired for toxicological and physiological reasons.
These include, in particular, residual amounts of compounds containing organically bonded chlorine, that arise as a consequence of the process, such as monochloroacetic acid (MCA) and, in particular, dichloroacetic acid (DCA) or salts thereof which are introduced into the end-product with the chloroacetic acid used.
Attempts to reduce the content of these compounds by prolonged reaction times or increasing the pH have not led to a significant reduction in impurity formation. The use of a pH above about 10, particularly at elevated temperatures around or above 100° C., brings with it the risk of increasing decomposition (DE-B-29 26 479, EP-B-0 557 835). DE-A-39 39 264 relates to a process for lowering the residual content of free alkylating agent in aqueous solutions of amphoteric or zwitterionic surfactants with the characterizing feature that the solutions are post-treated with ammonia, an amino acid having 2 to 8 carbon atoms or an oligopeptide. This post-treatment also causes a residual content of MCA and/or DCA to remain in the reaction product. In addition, however, as a result of the reaction products of ammonia and the alkylating agent or peptide and the alkylating agent, reaction products are produced which remain as impurities in the process product.
Furthermore, the reaction mixtures comprise large amounts of chloride ions in the form of their alkali metal or ammonium salts. For this reason, these prior art reaction mixtures have further disadvantages associated therewith, such as increasing the viscosity of the end-product, and impairing the low-temperature stability of formulations. Moreover, the prior art reaction mixtures cannot be formulated with a number of further active ingredients.
In addition, because of the content of chloride ions, prior art reaction mixtures are too aggressive for cleaning corrosion-sensitive metallic substrates which are used, in particular, in the electronics industry.
There has therefore been a number of attempts to remove these salts, such as, for example, by solvent extraction, as described in JP-A-759981984, or by electrodialysis according to EP-A-0 269 940. Apart from the fact that complete removal of chloride ions cannot be achieved, these prior art processes are complicated and economically disadvantageous due to the additional stages required.
There are also numerous processes which allow the oxidation of alcohols to carboxylic acids. In addition to the classical processes of oxidation on a laboratory scale by means of heavy metal oxides. (e.g. KMnO
4
), processes are known which can be carried out on an industrial scale, such as the oxidation by NO
2
(U.S. Pat. No. 5,856,470), by nitrile oxides (U.S. Pat. No. 5,179,218), by O
2
with noble metal catalysis (DE-39 29 063) or electrochemically (EP-A-0 199 413, DE-A-34 43 303).
From works by H. J. Schäfer (Overview: Topics in Current Chemistry, 1987, 142, 102 to 129), it is known that primary alcohols can be oxidized by electrolysis in alkaline solution using anodes coated with nickel oxide hydroxide NiO(OH) and steel cathodes to give the corresponding carboxylic acids with theoretical yields between 46 and 99%. The oxidization takes place primarily by an indirect anode process in which the alcohol is oxidized by the nickel oxide hydroxide with trivalent nickel to give the carboxylic acid, the NiO(OH) being reduced to nickel oxide or nickel hydroxide with divalent nickel. As a result of electron removal at the anode, the divalent nickel then converts back into trivalent nickel.
The electrochemical oxidation of alcohols that are bonded to a quaternary positively charged nitrogen via an ethylene group is not reported in the work by H. J. Schäfer.
SUMMARY OF THE INVENTION
In the endeavor to overcome the disadvantages of the prior art and to provide a process which permits the preparation of glycine derivatives that are free from organically bonded halogen and/or halide ions, it has now been found that this objective can be achieved by the oxidation of quaternary aminoalcohols. Surprisingly, the quaternary, positively charged nitrogen does not interfere in the oxidation process, and neither oxidation products of nitrogen, such as N-oxides, nor Hoffmann degradation products can be detected. Glycine derivatives which are prepared by the inventive method are free from inorganic chlorine or organically bonded chlorine, such as, in particular, monochloroacetic acid, dichloroacetic acid and salts thereof.
The oxidation of the quaternary aminoalcohol to the corresponding glycine derivative can be carried out in the present invention by electrochemical oxidation in aqueous alkaline solution using coated nickel electrodes.
The present invention thus provides a process for the preparation of glycine derivatives by oxidation of &bgr;-hydroxyethylammonium compounds by electrolysis of an aqueous alkaline solution, which comprises carrying out the oxidation using anodes coated with nickel oxide hydroxide.
The inventive process is notable for its extraordinary environmental friendliness since no environmentally detrimental byproducts form and, the use of highly toxic chloroacetic acid can be avoided. In addition, a product free from inorganic chlorine is obtained directly, therefore avoiding the technically complex separation of chloride ions.
DETAILED DESCRIPTION OF THE INVENTION
As stated above, the present invention provides a process for preparing glycine derivatives by electrochemically oxidizing hydroxyl groups of &bgr;-hydroxyethylammonium compounds present in an aqueous alkaline solution, i.e., an electrolyte, to give the corresponding acids.
By using the electrochemical process of the present invention, the theoretical yields obtained are, without exception, greater than 80%. The electrolysis of the present invention is in principle carried out in such a way that the aqueous electrolyte is electrolyzed at electrodes that are coated with nickel oxide hydroxide. The coating of the electrodes can be carried out by customary processes, such as, for example, according to the process proposed by H. J. Schäfer. In principle, an Ni(OH)
2
layer is cathodically deposited from an Ni salt solution on the later anode and then anodically converted, in an alkaline solution, into NiO(OH) (J. Kaulen, H. J. Schäfer,
Tetrahedron,
1982, 38, 3299).
Besides nickel metal, the anode materials to be coated with NiO(OH) include any material in which an activated nickel oxide hydroxide layer can adhere to, such as, for example, Monel, rust-free steel, graphite or a glassy carbon.
The cathode employed in the present invention can consist of any material customarily used in electrochemistry for the preparation of cathodes, such as, for example, noble metals, stainless steel or nickel.
The electrolysis cell employed in the present invention can consist of any material resistant to electrolyte and reactants, such as alkali-resistant glass, porcelain, polyethylene, rubber or stainless steel.
The cell type employed in the present invention may be divided or undivided, the latter being preferred since a reduction of the desired electrolysis product does not have to be feared.
The process a
Thurmüller Oliver
Tomuschat Phillipp
Goldschmidt AG
Scully Scott Murphy & Presser
Wong Edna
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