Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
  • C07H3/00—Compounds containing only hydrogen atoms and saccharide radicals having only carbon, hydrogen, and oxygen atoms
  • C07H3/02—Monosaccharides
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/01—Products
  • C25B3/07—Oxygen containing compounds
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/25—Reduction

Definitions

• D-ribose is very important in the synthesis of vitamin B It has been prepared commercially by the reduction of D-ribonolactone as shown by the following formulae.
• the electrolytic reduction is more advantageous than the chemical reduction.
• the electrolytic method heretofore reported employs mercury as the cathode, and an alkali metal salt of inorganic acid as the electrolyte which is capable of forming amalgam with mercury (e.g., J. Chem. Soc., Japan, vol. 70, p. 310 (1950), Pat. Publ. N0. 4359 (1950), Japan.)
• the yield of D-ribose is higher than that of the chemical reduction while the amount of mercury required is smaller. (Usually /3-% of the chemical reduction.)
• the electrolyte is an alkali metal salt of inorganic acid, there remain such defects as follow.
• the electrolytic reduction of D- ribonolactone may be improved by employing mineral acid-salts of primary, secondary or tertiary amines instead of alkali metal salts, as an electrolyte. According to this improved method, the yield of D-ribose may be increased, since the cleavage of D-ribonolactone may be substantially prevented.
• said electrolysis may be carried out in a standard electrolytic cell, which, for ex ample, consists of a glass beaker containing a small volume porous cup, sheet anode being within the porous cup, and mercury or amalgamated metal cathode being placed in the bottom of the cell.
• the electrodes are set in a direct-current circuit having an ammeter and variable resistance, and the beaker placed in a cooling bath.
• the catholyte is placed in the cathode compartment between the porous cup which is the semi-permeable diaphragm and the beaker wall, and the anolyte within the porous cup.
• the reduction is effected with stirring and cooling until the reaction is substantially completed, as evidenced for example by the increased evolution of hydrogen.
• the semi-permeable diaphragm of the electrolyticreduction apparatus is one which permits hydrogen ions to pass from the anode compartment into the cathode compartment and permits the passage of anions (e.g., sulfate or chloride) from the cathode compartment to the anode compartment, but is sufliciently impermeable to prevent diffusion of the catholyte component to be reduced into the anode compartment.
• anions e.g., sulfate or chloride
• Various materials are suitable for use as semi-permeable diaphragms for the electrolytic reduction, and may be so used for the purpose of this invention; inter alia, unglazed porcelain, filtros and notably Alundum.
• the anode for the purpose of this invention may be of any of the materials commonly used for the electrolytic reduction.
• the anode may be of lead, lead coated with lead dioxide, platinum and graphite.
• the cathode in this invention must be of mercury or amalgamated metal with mercury on its surface, for example, amalgamated lead, amalgamated silver, or amalgamated zinc, which have the hydrogen-overvoltage nearly equal to those of mercury.
• the anolyte for the purpose of this invention may be of the compositions commonly used for the electrolytic reduction, e.g., aqueous solutions of various concentrations of strong inorganic acids such as sulfuric, hydrochloric, or phosphoric acids.
• the anolyte is sulfuric acid in a concentration of about 0.5% to about notably a concentration of about 10%.
• the catholyte for the purpose of this invention is a non-alkaline aqueous solution of D-ribonolactone, i.e., a solution which contains D-ribonolactone, a sufiicient amount of acid to make the solution non-alkaline and a mineral acid-salt of primary, secondary or tertiary amine. It is most preferable to maintain the catholyte at a pH of '3 to 5.
• dilute hydrochloric acid, dilute sulfuric acid, boric acid, phosphoric acid, etc. may be referably used. Among them, boric acid and phosphoric acid are particularly suitable for this purpose.
• Suitable mineral acid-salts of amines are the sulfate, nitrate, hydrochloride or phosphate of the following amines; monoalkyl amine e.g., methyla'm-ine, ethylamine, propylamine, butylamine, amylamine, hexylamine, heptylamine, octylarnine; whydroxymonoalkylamine e.g., ethanolamine, prop'anolamine; dior tri-alkylamine e.g., dimethylamine, diethylamine, trimethyla'rnine; cycloalkylamine e.g., cyclohexylamine, lower phenylalkyl amine e.g., benzylamine, phenethylamine.
• monoalkyl amine e.g., methyla'm-ine, ethylamine, propylamine, butylamine
• the salts of amines I) illustrated below act as protonized amine ions (II) which may form amalgams of protonized amines 111) with mercury on the surface of cathode, and act similarly to those of alkali metal.
• the amalgams thus formed are unstable even at room temperature and degradate rapidly producing nascent hydrogen which is utilized for the reduction of D-ribonolaotone. '(Ref.: J .C.S. 1954, p. 760.)
• the electrolytic reaction of this invention may be illustrated by the following equations, wherein R represents hydrogen, alkyl, w-hydroxyalkyl, lower phenylalkyl or cycloalkyl radicals, R and R represent hydrogen or alkyl radicals, and X represents residue of mineral acid.
• D-ribonolactone is utilized efiieciently to produce D-ribose.
• Suitable concentration of the amine salt in the catholyte is not so high, because the amine salt is used as the source of protonized amine ion for the purpose of giving electric conductivity to the solution. Usually about 5% is most suitable for best results.
• the electrolysis may be effected at various amperages; e.g., 0.5 ampere and 15 amperes, and preferably 1 to 4 ampere/rim. of the cathode at various temperatures in which D-ribonolactone hardly decompose in the catholyte (e.g., between about to about 40 0.). Higher amperages require more eflicien't cooling of the electrolytic-reduction cell.
• the above mentioned temperature, voltage, amperage and current density are not critical in the process of this invention.
• EXAMPLE 1 20 ml. of mercury purified by distillation was placed as the cathode in the bottom of a 300 ml. glass electrolytic cell having a 36 cm. base. A platinum plate having an area of 10 cm. is used as the anode and the plate is set in a diaphragm made of unglazed porcelain. 30 ml. of 10% sulfuric acid was used as the anolyte. A solution dissolving 3.3 g. of D-ribonolactone, 4 g. of methylamine sulfate, 3 g. of boric acid in ml. of distilled water was used as the catholyte. A stirrer and the thermometer were placed in the cell and the cell was cooled With ice water from outside.
• the electrolysis was carried out with vigorous stirring under such condition that the temperature of catholyte is at 10-30 C., the current is one ampere, and the current density of the cathode is 2.8 ampere/dmF.
• the electrolysis was stopped, and the catholyte was separated.
• the solution was adjusted to litmus alkalinity with 10% sodium hydroxide, subsequently it was neutralized with 10% sulfuric acid, and concentrated at a temperature lower than 40 C. at a reduced pressure.
• the residue was extracted with hot methanol, and the extract was concentrated to a syrup containing D-ribose.
• the electrolysis was carried out under the same conditions as in Example 1 with the exception that 4 g. of methylamine sulfate was replaced by 5 g. of ethylamine sulfate, the electro'lyzing current is 1.5 ampere and the current density of the cathode is 4.2 ampere/dm. After 'two hours, the content of D-ribose in the catholyte reached the maximum, and the electrolysis was stopped. The catholyte was treated similarly to Example 1 and 2.9 g. of the crystalline D-ribose was obtained.
• the amalgamated metals could not be used advantageously in the prior methods, they may be used as the cathode in this invention.
• the necessary amount of mercury for carrying out the electrolytic reduction of D-ribonolactone is only one hundredth as much as the case of mercury cathode.
• the amine is not susceptible to any unfavorable changes throughout the electrolysis, and may be easily recovered from the reaction mixture by distillation after separating the crystalline D-ribose and adjusting the pH to a strong alkalinity.
• a silver sheet having an area of 30 cmfi was amalgamated on its surface by soaking in dilute nitric acid and exposing its metallic surface subsequently to mercury.
• the electrolysis was carried out under the same condi tions as in Exam 1e 1 with the exceptions that mercury cathode was replaced by the amalgamated silver sheet prepared above and 4 g. of methylamine sulfate was replaced by 5 g. of ethylamine sulfate, and the current density of cathode is 3.3 ampere/dm. After three hours,
• the process for preparing D-ribose which essentially comprises charging an electrolytic cell, having anodic and cathodic compartments separated by a semipermeable diaphragm, with a non-alkaline, aqueous solution in which D-ribonolactone and a salt of an amine selected from the group consisting of mineral acid-salts of monoalkyla'm'ine, dialkylamine, trialkylamine, whydroxymonoalkylamine, cycloalkylamin and lower phenylalkylarnines are dissolved as the catholyte, and as the anolyte an aqueous solution of a strong inorganic acid, said acid being substantially non-reactive with the anode material, and said cathode being mercury or amalgamated metal with mercury on its surface, passing References Cited UNITED STATES PATENTS 3,312,608 4/ 1967 Sugasawa et al. 204-73 FOREIGN PATENTS 134,236 9/

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Citations (2)

• 1964
  • 1964-07-23 CH CH968064A patent/CH451900A/de unknown
  • 1964-07-24 US US385034A patent/US3380901A/en not_active Expired - Lifetime
  • 1964-08-07 GB GB32346/64A patent/GB1007642A/en not_active Expired

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