Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C241/00—Preparation of compounds containing chains of nitrogen atoms singly-bound to each other, e.g. hydrazines, triazanes
  • C07C241/02—Preparation of hydrazines
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C243/00—Compounds containing chains of nitrogen atoms singly-bound to each other, e.g. hydrazines, triazanes
  • C07C243/10—Hydrazines
  • C07C243/22—Hydrazines having nitrogen atoms of hydrazine groups bound to carbon atoms of six-membered aromatic rings
• • 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

• ABSTRACT OF THE DISCLOSURE A process for the manufacture of phenylhydrazine by cathodic reduction with separation of cathode and anode spaces by a diaphragm wherein diazoaminobenzene dissolved in an electrolyte is reduced on solid electrodes.
• the present invention relates to a process for the manufacture of phenylhydrazine.
• the technical accomplishment of the diazotate reduction is additionally impeded by the fact that it is an indirect electro-chemical reduction (F. Fichter, Organische Elektrochemie 1942, page 223).
• the diazotate is not reduced directly by the absorption of electrons from the cathode but by the cathodically produced sodium amalgam. It is therefore not surprising that poor yields are obtained when other cathode materials that are better suited for a technical performance are used in the reduction of aromatic diazotates (F. Fichter, E. Willi in Helvetica 17 (1934) page 1418).
• phenylhydrazine undergoes relatively easy reductive scission. With hydrogen on nickel, aniline and ammonia are obtained in a quantitative yield at atmospheric pressure and normal temperature. (H. Rupe, E. Hodel in Helvetica 6 (1923) page 873). With zinc and hydrochloric acid the quantitative scission of phenylhydrazine can also be obtained (E. Fischer, Liebigs Annalen 239 (1887) page 248).
• phenylhydrazine can be obtained by cathodic reduction in a good yield by reducing diazoaminobenzene, dissolved in an electrolyte on solid electrode materials such as lead, zinc, zinc-titanium alloy, cadmium, tin and surprisingly also copper and graphite.
• solid electrode materials such as lead, zinc, zinc-titanium alloy, cadmium, tin and surprisingly also copper and graphite.
• copper and graphite have a distinctly lower hydrogen over-voltage than, for example, lead or mercury and, therefore, they ought to be less suitable for the reduction of diazoaminobenzene.
• the use of copper or graphite as electrode material gives very high yields of phenylhydrazine even in galvanostatic electrolysis, i.e. under technically interesting conditions.
• the electrolysis tempera ture can be varied in a wide range and its upper limit is only given by the thermal decomposition of the diazoaminobenzene.
• a temperature in the range of from '20 to C., especially +15 to +60 C. is preferred.
• the electrolysis is preferably carried out with aqueous electrolytes.
• the common solvents such as alcohols, ethers, carboxylic acid amides and/or nitriles or mixtures thereof are suitably added as organic cosolvents.
• the diazoaminobenzene can be prepared either before-hand according to known processes in a separate reaction or directly in the catholyte from aniline. Besides the high yield and the largely variable electrolysis temperature, the process of the invention therefore has the further advantage that the aniline obtained in the cathodic dissociation of diazoaminobenzene can be used again for preparing fresh diazoaminobenzene.
• a sufiicient conductibility of the catholyte is preferably obtained in known manner by adding suitable conducting salts.
• the pH-value of the catholyte has to be chosen in such a manner that the diazoaminobenzene cannot be split to give benzenediazonium salt and aniline, a pH- value above 5, especially about 6 to 14 being preferred. Higher pH-values are also possible but they do not offer any advantage.
• Suitable conducting salts are preferably alkali metal and ammonium hydroxides as well as organic bases, for example the various tetraalkyl ammonium hydroxides.
• electrolysis cells there can be used all common cells with separation of cathode and anode space by diaphragms.
• diaphragms there can be used all common materials provided that they are stable to alkali and/or acids as well as the used organic solvents.
• ion exchange diaphragms more particularly anion exchange diaphragms.
• phenylhydrazine obtained without choosing the optimum conditions. It is obvious that by variation of the electrolysis conditions better yields can be obtained.
• the phenylhydrazine can be obtained not only in the form of the hydrochloride as described in the following examples but also by separation from the aniline without acidifying the catholyte, for example by distilling off the solvent from the catholyte directly and working up by distillation the mixture of phenylhydrazine and aniline then separating.
• the material yields are calculated on the amount of diazoaminobenzene used as in the chosen acid working-up of the catholyte, this is resplit into benzenediazonium salt and aniline so that the unreacted portion of the starting substance is not determined directly.
• the opposite end of the tube was screwed into a polyethylene stopper provided with standard ground joint so that the cell was tightly closed.
• the stopper had the necessary standard ground borings for thermometer, bubble counter and inert gas inlet.
• As anode a stainless steel (V4A)spiral was used.
• the anolyte was 3 N KOH.
• the catholyte contained 0.1 mol (19.7 g.) diazoaminobenzene dissolved in 200 ml. of a mixture of methanol/ 3 N KOH in a ratio of 20:1.
• the electrolysis temperature was in the range of from 2833 C. 10.7 a./h r. of current were passed potentiostatically at l800 mv. (against Ag/AgCl) through the cell, whereupon the initially deep blackish red nontransparent solution had turned pink.
• the solution was acidified with HCl, methanol was distilled 011, the residue was taken up in concentrated hydrochloric acid and the phenylhydrazine hydrochloride remaining as a precipitate was filtered 01f with suction.
• the salt was suspended in water, the suspension was rendered alkaline with NaOH whereby the free phenylhydrazine separated. It was repeatedly extracted with ether, the combined ether phases were dried and the ether was distilled 011. 10.2 g. of phenylhydrazine were obtained.
• EXAMPLE 2 Electrolysis was carried out in the cell described in Example 1, with the exception that an electrographite disc having a surface of 40 cm. was used. 11.5 a./hr. were passed galvanostatically at 2 ampere through the mixture consisting of 200 ml. methanol/3 N KOH (20:1) and 19.7 g. (0.1 mol) diazoaminobenzene. The material yield of phenylhydrazine was 89%, the current efficiency 83%.
• EXAMPLE 4 Electrolysis was carried out in a flow cell consisting of 2 equally large square polyethylene halves between which the anion exchange diaphragm (commercial name Nepton A 111 BZL 183) was clamped. The etfective cathode surface was 115 cm. To obtain a uniform substance transport the electrode spaces were divided in four trajectories by conducting strips resting on the electrodes and the diaphragm. The distance cathode to diaphragm was 6 mm. Lead was used as cathode material, platinum as anode material.
• the electrolytes (anolyte: 700 ml. 3 N KOH; catholyte: 1000 ml. 0.5 molar diazoaminobenzene in methanol/ 3 N KOH (20:1)) were circulated by a pump with a flow speed of about 15 cm. per second. 6.7 a./hr. current were passed galvanostatically at 18 amperes.
• the reaction mixture was worked-up as in Example 1 whereby phenylhydrazine was obtained in a material yield of 91.5% or a current efliciency of 73%.
• Phenylhydrazine is a valuable intermediate product and starting product for pharmaceutical and dyestuffs.
• Process for the manufacture of phenylhydrazine by cathodic reduction with separation of cathode and anode spaces by diaphragm which comprises reducing at a cathode selected from the group consisting of cadmium, copper, graphite, lead, tin, zinc and an alloy of zinc and titanium material diazoaminobenzene dissolved in an electrolyte comprising water, an organic cosolvent, and a conductive compound selected from the group consisting of alkali metal hydroxide, ammonium hydroxide, an organic base and mixtures thereof at a pH above 5 and a temperature between 20 to C.
• a cathode selected from the group consisting of cadmium, copper, graphite, lead, tin, zinc and an alloy of zinc and titanium material diazoaminobenzene dissolved in an electrolyte comprising water, an organic cosolvent, and a conductive compound selected from the group consisting of alkali metal hydroxide, ammonium hydroxide, an organic

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (1)

• 0
  • BE BE791636D patent/BE791636A/xx unknown
• 1971
  • 1971-11-20 DE DE2157608A patent/DE2157608C3/de not_active Expired
• 1972
  • 1972-11-16 CH CH1667572A patent/CH574912A5/xx not_active IP Right Cessation
  • 1972-11-17 IT IT31845/72A patent/IT971015B/it active
  • 1972-11-17 GB GB5324572A patent/GB1388708A/en not_active Expired
  • 1972-11-17 BR BR8092/72A patent/BR7208092D0/pt unknown
  • 1972-11-17 NL NL7215600A patent/NL7215600A/ unknown
  • 1972-11-17 JP JP47114875A patent/JPS4861436A/ja active Pending
  • 1972-11-20 US US00307776A patent/US3836440A/en not_active Expired - Lifetime
  • 1972-11-20 FR FR7241097A patent/FR2160665B1/fr not_active Expired

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