US3702871A - Preparation of polyhalo phenols - Google Patents

Preparation of polyhalo phenols Download PDF

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Publication number
US3702871A
US3702871A US832849A US3702871DA US3702871A US 3702871 A US3702871 A US 3702871A US 832849 A US832849 A US 832849A US 3702871D A US3702871D A US 3702871DA US 3702871 A US3702871 A US 3702871A
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hydrolysis
glycol
solvent
mixture
mols
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Edwin B Michaels
John W Lee
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EDWIN B MICHAELS
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EDWIN B MICHAELS
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
    • C07C37/01—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by replacing functional groups bound to a six-membered aromatic ring by hydroxy groups, e.g. by hydrolysis
    • C07C37/02—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring by replacing functional groups bound to a six-membered aromatic ring by hydroxy groups, e.g. by hydrolysis by substitution of halogen

Definitions

  • the present invention relates to the manufacture of polyhalophenols from a polyhalobenzene containing at least one halogen in excess of converted product utilizing alkaline hydrolysis in the presence of an aliphatic diol and an hydrolysis controlling reagent under reflux conditions.
  • the invention relates to an improved alkaline hydrolysis process for converting, under reflux and in the presence of an aliphatic diol solvent, polyhalobenzenes to polyhalophenols containing at least one less halogen atom than the polyhalobenzenes being treated, while utilizing an hydrolysis controlling reagent or water entraining reagent, whereby less than 1% of the treated polyhalobenzene remains unhydrolyzed, and recovering aliphatic diol therefrom.
  • the invention is concerned with aliphatic diol recovery from a hydrolyzed reaction mixture of polyhalogenated benzenes, specifically, from the alkaline hydrolysis of l,2,4,5-tetrachlorobenzene in the presence of a solvent, such as ethylene glycol or propylene glycol, resulting in the recovery of an alkali salt of 2,4,5-trichlorophenol from a pH controlled menstruum subsequent to dis tillation of said solvent.
  • a solvent such as ethylene glycol or propylene glycol
  • polyhalogenated benzenes and, particularly, 1,2,4,S-tetrachlorobenzene can be hydrolyzed by diverse methods, each of which is not wholly satisfactory with respect to overall yield, purity and control of reaction.
  • alkaline hydrolysis of chlorinated benzenes utilizing caustic soda proceeds with great difiiculty except under eXteme conditions of high temperature and high pressure.
  • sundry alcohols as for example, methanol or glycol, have been employed in an hydrolysis mixture so as to control the rate of the polyhalobenzene hydrolysis. In this manner, only a single hydroxyl group will appear on the benzene moiety.
  • glycol or propylene glycol from the hereinabove defined hydrolysis mixture containing less than 1% unreacted polyhalobenzene. It is a still further object of the invention to recover by distillation a pure halogenated phenol from a crude halogenated phenol material by admixing ammonia or ammonium hydroxide therewith.
  • a polyhalobenzene there is admixed in a suitable reactor equipped with agitation and condenser a polyhalobenzene, an aliphatic diol, a hydrolysis controlling reagent and an alkali metal hydroxide in amounts hereinbelow stated, at a temperature of about 160-180 C., azeotroping 2 mols of water per mol of said polyhalobenzene while maintaining the aliphatic diol in the reaction menstruum, then increasing the temperature to from about 190 C. to about 210 C. so as to complete the hydrolysis reaction and removing substantially all of the hydrolysis controlling reagent. Less than 1% of the polyhalobenzene remains in the hydrolyzed medium.
  • the latter medium is neutralized to remove excess alkali metal hydroxide by acid addition to a pH between 11 and 13, vacuum distilling resultant neutralized medium to remove aliphatic diol therefrom and, thereafter, recovering 2,4,5-trichlorophenol in good yield and purity.
  • the aforementioned temperature range is critical to obtain less than 1% of unhydrolyzed polyhalobenzene. This is highly desirable to prevent clogging of the condenser when an attempt to recover the aliphatic diol solvent is made. Moreover, if a reaction mixture containing more than 1% of unhydrolyzed polyhalobenzene and the desired hydrolyzed product were acidified, the unhydrolyzed polyhalobenzene would be present as a diflicult-to-remove impurity.
  • Illustrative of the polyhalobenzenes containing three to six halogen atoms which can be hydrolyzed by the process of the invention are: 1,2,4,S-tetrachlorobenzene, 1,2,3,5- tetrachlorobenzene, 1,2,4-trichlorobenzene, 1,2,4-tribromobenzene, or 1,2,3,4,5,6-hexachlorobenzene.
  • Exemplary of the aliphatic diols contemplated herein are: glycol or propylene glycol, in amounts ranging from not less than 5 to about 8 or more mols and, preferably 6 mols, per mol of polyhalobenzene.
  • sodium hydroxide potassium hydroxide or lithium hydroxide.
  • an amount ranging from 2.2 to 3 mols, and, preferably, 2.5 mols per mol of polyhalobenzene is a good practice.
  • Illustrative hydrolysis controlling reagents which can be mentioned are: (a) an alkane containing from 6 to 12 carbon atoms, or mixture thereof, namely, hexane, heptane, octane, nonane, decane, undecane, dodecane, deordorized kerosene or mineral spirits having a boiling point range between 160 C. and 180 C.
  • a monoor dialkyl benzene containing from 2 to 4 carbon atoms in the alkyl substituent such as xylene o-ethyl benzene, n-propyl benzene, o-isobutyl benzene, 1,4 diethylbenzene, 1-ethyI-4-n-propyl benzene, n-butylbenzene, or halogenated benzenes, such as o-dichlorobenzene and isomers thereof, in amounts ranging from 0.01 mol to 0.5 mol, and, preferably, 0.07 mol per mol of polyhalobenzene to be treated.
  • a monoor dialkyl benzene containing from 2 to 4 carbon atoms in the alkyl substituent such as xylene o-ethyl benzene, n-propyl benzene, o-isobutyl benzene, 1,4 diethylbenzen
  • the aforementioned four components of the mixture are all admixed in a suitable reactor containing condenser under agitation at a temperature below reflux, usually between C. and C.
  • Hydrolysis then proceeds in two heating stages, namely, under reflux at temperatures ranging from about C. to about C. for a time sufiicient to collect as a distillate 2 mols of water and then completing the hydrolysis at a temperature between about C. and about 210 C., usually between 0.3 and 3 hours.
  • Hydrolyzed mixture substantially free from unhydrolyzed polyhalobenzene is next acidified with any mineral acid, such as hydrochloric acid or sulfuric acid, so as to reduce the pH of the hydrolysis mixture from about 14 to from 11 to 13, and preferably to a pH from 12 to 12.5. Thereafter, the so-pH adjusted hydrolyzed mixture is subjected to vacuum distillation, preferably at from about 5 mm. Hg to about 30 mm. Hg, at a base temperature of from 100 C. to 170 C. to recover the aliphatic diol of adequate grade and purity for reuse.
  • any mineral acid such as hydrochloric acid or sulfuric acid
  • Resultant residue remaining in the distillation flask is admixed with suflicient water to dissolve the alkali metal phenate formed during hydrolysis.
  • suflicient mineral acid such as sulfuric acid
  • To the water layer is added suflicient mineral acid, such as sulfuric acid, to further reduce the pH of the mixture to from 4 to 4.5, whereby the recovered alkali metal phenate is converted to the corresponding halogenated phenol.
  • Two layers form. The upper water layer is discarded, but the lower layer containing the phenol is washed several times with water at temperatures ranging from about 65 C. to about 100 C. to recover desired halogenated phenol.
  • EXAMPLE 1 To a stainless steel reaction vessel equipped with condenser and stirrer, are admixed with agitation 0.07 mol of mineral spirits boiling between 160 C. and 180 C., 6 mols of glycol, 1 mol of tetrachlorobenzene and 2.5 mols of sodium hydroxide, While heating to a temperature of about 140 C. The mixture is next heated to reflux temperatures ranging from between 160 C. and 180 C. for about 0.75 hour to 3 hours to distill a binary azeotropic mixture of Water and mineral spirits of 4/6 volume ratio and collecting 2 mols of water, While returning the mineral spirits to the reaction. The heating rate is so regulated as to maintain within the condenser a vapor temperature of from 95 C.97 C.
  • glycol is found to be entrained in the binary azeotrope in amounts usually in excess of 5%. If, as a result of such glycol removal, the hydrolysis mixture falls below the critical 5 mols, there is created a potentially explosive environment.
  • the hydrolysis reaction is not spontaneous.
  • the hydrolysis of the tetrachlorobenzene is about 90% complete.
  • the temperature is next increased to between 190 C. and 195 C. for from 0.3 to 3 hours. All the mineral spirits as Well as any residual free Water are thereby distilled.
  • the direct recovery of glycol by distillation therefrom cannot be readily achieved because the tetrachlorobenzene clogs or blocks the condenser thereby prohibiting egress and recovery of the glycol solvent.
  • Residual sodium salt of 2,4,5-trichlorophenol, free of glycol, is next acidified with sulfuric acid to a pH of 4.5
  • Example 2 The hydrolysis procedure of Example 1 is followed in every material aspect except there are admixed 4 mols of glycol, 3.5 mols of sodium hydroxide, 1 mol of tetrachlorobenzene and 0.25 mol of xylene as the hydrolysis mixture. After initial water and xylene removal at a temperature of 155 C. instead of 160 C., the reaction medium became exothermic and the temperature rose to 250 C. within five seconds. The resultant hydrolysis reaction which was uncontrollable was terminated at this point while noting a tarry mass as a residue.
  • the aforementioned conditions for effecting hydrolysis involving a two-step heating range namely one from (a) 160 C. to 180 C. and (b) 190 C. to 210 C. with the subsequent recovery of the aliphatic diol solvent, are all critically interrelated.
  • the present reaction system maintains thermal stability at temperature even as high as 240 C.
  • glycol solvent is lost and degradation reactions and formation of toxic compounds as well are all possible. Therefore, the times and temperatures herein recited are critical and must be maintained.
  • temperatures in excess of C in the absence of glycol or propylene glycol hydrolysis, say hydrolysis in methanol solvent, temperatures in excess of C.
  • a process for the preparation of a polychlorophenol or polybromophenol containing one less halogen atom than the corresponding polychlorobenzene or polybromobenzene from which it is prepared by alkaline hydrolysis which comprises the steps of:

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US832849A 1969-06-12 1969-06-12 Preparation of polyhalo phenols Expired - Lifetime US3702871A (en)

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