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

Definitions

• the invention relates to a process for the preparation of 2,2'-dichlorohydrazobenzene by catalytic reduction of o-nitrochlorobenzene with hydrogen.
• the temperature is between 40-100 ° C, preferably 60-70 ° C
• the hydrogen (excess) pressure is about 0.4-7.8 bar (20-125 psi, abs.), Preferably about 0.75 up to 1.8 bar (25 - 40 psi, abs.).
• naphthalene derivatives such as naphthoquinone- (1,4) or 2,3-dichloro-naphthoquinone- (1,4) are added to the reaction mixture.
• the yields of 2,2'-dichlorohydrazobenzene obtained in this way vary between 80 and 90%, and the chlorine elimination is said to be low.
• anthraquinone preferably hydroxyanthraquinones
• co-catalysts e.g. ⁇ -hydroxyanthraquinone or 2,6-dihydroxyanthraquinone can be added.
• the noble metal catalysts can be recycled very often when the anthraquinone derivatives are used, without suffering a drop in activity. Even after e.g. Ten times the precious metal catalysts are used, constant yields are obtained in the same reduction time as in the starting batch.
• the anthraquinone derivatives accelerate the reduction of the individual reaction stages, in particular the azoxy and azo stage, much more strongly than naphthoquinone compounds, so that a lower temperature throughout the Reaction time is enabled and even shorter reaction times can be achieved than when using the known naphthoquinones.
• Another advantage is that e.g. the ß-hydroxyanthraquinone after the reduction from the aqueous mother liquor by setting a pH of 3 to 4 can be precipitated practically quantitatively and can be used several times without purification, while the 2-hydroxy-3-chloronaphthoquinone- (1,4) (formed during the reduction from 2,3-dichloronaphthoquinone (1,4)) has to be eliminated by a complex wastewater treatment.
• the amount of ahthraquinones used is low, it is lower than that of the naphthoquinone derivatives.
• a weight ratio of ß-hydroxyanthraquinone to o-chloronitrobenzene of 0.003 to 0.008, in particular 0.004: 1 is sufficient to evenly reduce the dichlorazoxybenzene which occurs as an intermediate via the dichlorazobenzene to the hydrazo compound, while of 2,3-dichloronaphthoquinone- (1,4) twice the amount is necessary in order to achieve comparable results at least when the noble metal catalysts are used for the first time.
• the precious metal catalyst is more reliable Reproducibility of the yields and product properties even after repeated use - need only be used in a weight ratio of nitro compound to platinum or palladium between about 4000: 1 and 1500: 1, preferably 2500: 1.
• a 16 to 25% sodium hydroxide solution is used as the reaction medium in such an amount that after the end of the reaction a 10 to 15% sodium hydroxide solution is formed by the water of reaction formed.
• anthraquinones show advantages over the naphthoquinones. While the best results are achieved with naphthoquinone with a 16% sodium hydroxide solution in a weight ratio of o-nitrochlorobenzene to NaOH (100%) such as 1: 0.095, the anthraquinones allow an increase in the NaOH concentration to 25% and a lower use of sodium hydroxide solution in a weight ratio of o-nitrochlorobenzene to NaOH (100%) such as 1: 0.071, without slowing down the reaction rate.
• the use of an approx. 25% NaOH means an improvement in the space yield of approx. 20% compared to a 16% NaOH according to the above weight ratios.
• the reaction temperature is preferably between 55 to 60 ° C., the hydrogen pressure preferably between 1 to 6 bar, it being advantageous to let the pressure rise slowly within the specified limit values during the reduction.
• the reduction of o-nitrochlorobenzene to 2,2'-dichlorohydrazobenzene is carried out using a water-immiscible solvent, such as e.g. Benzene, toluene, xylene, ethylbenzene or their technical mixtures, for example the mixture of m-xylene and ethylbenzene, which is commercially available under the name "Solventnaphtha".
• a water-immiscible solvent such as e.g. Benzene, toluene, xylene, ethylbenzene or their technical mixtures, for example the mixture of m-xylene and ethylbenzene, which is commercially available under the name "Solventnaphtha".

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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Citations (2)

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• 1977
  • 1977-07-27 DE DE2733747A patent/DE2733747C2/de not_active Expired
• 1978
  • 1978-07-14 DE DE7878100394T patent/DE2860060D1/de not_active Expired
  • 1978-07-14 EP EP78100394A patent/EP0000519B1/fr not_active Expired
  • 1978-07-25 IT IT26090/78A patent/IT1097303B/it active
  • 1978-07-25 US US05/927,856 patent/US4217307A/en not_active Expired - Lifetime
  • 1978-07-26 CA CA308,185A patent/CA1111449A/fr not_active Expired
  • 1978-07-26 JP JP9056478A patent/JPS5424838A/ja active Granted

Patent Citations (2)

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