CA1064521A - 2,2,6,6-tetrahalocyclohexanone - Google Patents

Abstract

ABSTRACT
2,2,6,6-Tetrachlore(or tetrabromo)cyclohexanone is prepared by reacting in the liquid phase chlorine or bromine with a cyclohexanone compound of formula where Y is hydrogen or chlorine (to produce the tetrachloro compound) or hydrogen or bromine (to produce the tertrabromo compound) is the presence as catalyst of tributyl phoshine or a salt thereof.
A pyprogallol compound of formula I
wherein R1, R2 and R3 each represent hydrogen or alkyl of 1-6 carbon atoms, or a salt thereof, is prepared by hydrolysing the corresponding 2,2,6,6-tetrachlorocyclohexanone or 2,2,6,6-tetrabromocyclohexanone.

Description

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.
q~is invention relates to a proce~s for producing

2,2,6,6-tetrahalocyclohexanone compounds, more particularly 2,2,6,6-tetrachlorocyclohexanone and 2,2,6,6-tetrabromocyclo-hexanone.
It is possible to produc~ 2,2,6,6-tetrachlorocyclo-hexanone or 2,2,6,6-tetrabromocyclohexanone by chlorinating or bromin~ting cyclohexanone. AlternatiYely, 2,2,6~6-tetra- ~ ;
chlorocyclohexanone can be prepared by chlorinating cyclohexanol.
~ owever it has been found, in accordance with the present invention, that 2,2,6,6-tetrachlorocyclohexanone or 2,2,6,6-tetrabromocyclohexanone can be prepared by reacting in the liquid phase, in the case of the production of 2,2~6,6-;:~ tetrachlorocyclohexanone, chlorine, or in ~he case of the production of 2,2,6,6-tetrabromocyclohexanone, bromine, with a~cyclohexanone compound of ormula , ~ :

. : : : O
: y ~ C -H
H ~~ H
H ~ ~` C ~ ~ H

where each~ is the same or dif~erent and represents~ in the cà~e~of~the~produation of 2,2,6:,~6-tetrachloroayclohexanone, an atom of hydro~3en or chlorine, and in the ca~e of the :~
20~ productlon:of 2,2J696-tetrabromoayclohexanon~, an atom of hydrogen or brom:ine, in the presence of a catalyst selected rom tributy~phosphine or a salt thereo.

~- :

`" 1~6gLS~
As disclosed in copending Canadian patent application No. 266,365 filed concurrently herewith, for an invention of John Frederick Harris and Barrie James Magill, 2,2,6,6 tetrachlorocyclohexanone and 2,2,6,6-tetrabromocyclo-hexanone are useful for producing pyrogallol compounds.
Pyrogallol or its derivatives have various uses, for instance as photographic developers, in dyeing leather and wool, in the analysis of heavy metals and as intermediates e.g. in the production of the insecticide 2,2-d:imethyl-1,3-benzodioxol-4-yl methylcarbamate~ At present, all the pyrogallol available in commerce is prepared by decarboxylation of gallic acid obtained from comparatively rare plant sources. This makes pyrogallol expensive and difficult to procure. Similarly pyrogallol derivativés are expensive and difficult to procure. The process of the above mentioned Canadian application of Harris and Magill avoids such rare plant sources and synthesises the ; product readily. More particularly~ a pyrogallol compound of formula OH

.:
whereln Rl, R2 and R3 are the same or different and each !~
represents a hydrogen atom or an alkyl group of 1-6 carbon àtoms, or a salt thereo~, is produced by a process which comprises hydroly~ing a 2,2,6r6-tetrahalocyclohexanone compound ; of~ormula ~ ~ .
~:: : : :

~ 3 - -~

`` ~LC~6~5Z~
X ~X
~X II
H~¦ ,~
R~< ~R3 E~ R2 wherein each X i~ the Rame and repre~ent3 a chlorine or bromine atom; and Rl, R2 and ~3 are a~ def ined above.
The process enable~ the pyrogallol compound or sal thersof to lbe ~ynl:h~si~ed in very high yields and in a hiyh state of purity.
~ he pyrogallol compound ~orms salts by rea~on of it~
phenolic OH group3. 'rhe~ pyrogallol compound car~ be in the form of it~ salt~. The salts in~lude particularly alkali metal, eOg. sodium or potassium9 e~pecially sodium, ~alts and can be prepared from the lO pyrogallol compound itself in convsntional ways, e . g. b~ reaction with alkali me~al alkoxides. The pyrogallol s:~mpourld it~elf can be ~: pr~pared from~ it~ salts in coDventic:~nal way~ aOgo by reaction with : ~ acid for example hydrochloric acid, Usually the pyrogallol compoun~l it~elf rat}-er han a salt ~: th~3raof i9 formed in th~3 above mentioned hy~roly~i~, and tha pyro- `:
gallol compound can be converted to a ~alk thereo if desired though thi~ not pre~erredO
Preferably X repre~nt~ a chlorine atom. The alkyl group whl~h Rl, R2 or R3 may repre~ellt may be for example~ methyl7 e hyl ;

or preferably t-butyl. The hydrolysis is of particular interest where at least two of R , R and R , preferably at least R and R3, each represents a hydrogen atom. Thus, in a particular embodiment Rl and R3 each represent a hydrogen atom and R2 represents t-butyl. Most preferred, however, is Rl, R2 and R3 each representing a hydrogen atom, so that the pyrogallol compound or salt thereof is pyr~gallol itself or a salt thereof.
The hydrolysis may be considered over all:

O OH
X~x HO ~WH
X + 2N O ~ I +4HX

The hydrolysis can be effected directly or indirectly. Direct hydrolysis is the reaction of the tetra- -halocyclohexanone compound itself with water. Indirect hydrolysis is the reaction of the tetrahalocyclohexanone compound to form a derivative which is reacted with water in a separate stage. Indirect hydrolysis can be carried out for example by reacting the tetrahalocyclohexanone compound with a metal (e.g. sodium, potassium, calcium or aluminium)alkoxide (e.g. derived from an alkanol of 1-4 carbon atoms), preferably sodium methoxide, ollowed by acid hydrolysis, for example by hydrochloric acid. Direct hydrolysis, however, enables the .
over all reaction to he conducted in a smaller number of stages, and is preferred.
The yield in the direct hydrolysis can be improved .

~ _ 5 _ : ~, , , , ~ . ' ~

~ 645~1 dramatically by employing a ~atalyst. A wide range of materials act a~ catalysts in thi re~pect. 1~ere can be u~ed as catalyst a b~se or an anionO An anion is included within ~ome definition~
of a base, but in the pxesent speci~ication we prefer to dif-ferentiate between themO The base can be for example morpholine, triethanolamine, cyclohexylamine, di-n-butylamine or 2-(diethyl~
amino)ethanol or an anion exchange resin.
The cataly~t is preferably, h~wever, an anion. S~itable anion~ include (A) the anionic part of a cation exchange re~in (e.g~ a carboxylic acid cation exchange re~in) in the hydrogen or salt form (e~g. the sodium, pota~sium, calciwm or ammonium form)~
e.g. Am~erlite IRC 50 in the hydrogen or ~odiwm orm, or9 pref~rably, (B) an anion of another ~alt (called herein a ~imple ., salt to differentiate it f rom the ion exchange re~in salt) eOgO ~.
citratc, ~ihydrogen citrat~, hydrogen citrate, acetateJ
monochloroacetate, hydrogen malate, ~alate9 hydrogen phthalate, : , :
: ~hydrogen i~ophthalate, hydrogen tartrate, tartrate, oxalate OOCCOO ), o-nitrobenzoate, benzoate, lactate, propionate, ~: glycolata, malonate ( OOCCE~2COO-)~, formate, salicylate, (~IOC~H4COO~

:: ~ hydrogen adipate, adipate, hyd~ogen pho~phate, dihydrogen : 20 phosphate, picolinate, furoate9 dihydrogen pyrophosphato, hydrogen :, , ~uccinate, ~ulphamateJ hydrogen pho~phite, gluconata, borate (H2BO3- ) or ~luoride, q!he anion o~ a s~ple salt i~ preferably employed in the ~ 6 -;, .

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form of a simple salt rather than the acid. The anion catalyst can be in the form of a water-soluble metal, ammonium, or amine, salt or a mixture thereof. The amine salt can be that of a primary, secondary or tertiary amine. The amine can be aliphatic, aromatic or heterocyclic or an amine containing a mixture of such substituents on the amine nitrogen atom. It is generally preferred to use the sodium, potassium, ammonium or morpholine salt. The salt can be admixed as such or lt can be generated in situ, e.g. by reacting acid from which the salt is derived with alkali. For instance, cation exchange resin in the salt orm can be generated in situ by providing the resin in the hydrogen form and having alkali present. Alternatively, the salt may be formed ln situ by employing an ester, such as -~
methyl oxalate, in the presence of an alkali.
Specific simple salts which are catalysts include trisodium citrate, mono-morpholine citrate, di-morpholine citrate, sodium dih~dr ~en citrate, disodium hydrogen citrate, sodium acetate, sodium~chloroacetate, sodium hydrogen malate, dlsodium malate, sodium hydrogen phthalate, potassium hydrogen 20~phthalate, ammonium hydroyen phthalate, sodium hydrogen sophthalate, sodium hydrogen tartrate, disodium tartrate, disodium oxalate, sodium o-nitrobenzoate, sodium benzoate, sodium lactate, sodium propionate, sodium glycolate, disodium ~ : :
malonate, sodium formate, monosodium salicylate, sodium hydrogen adipate, disodium adipate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium picol:inate, sodium furoate ~LCI16~5;Z1 disodium dihydrogen pyrophosphate, sodium hydrogen succinate, sodium sulphamate, sodium hydrogen phosphite, sodium gluconate, monosodium borate, and potassium fluoride.
In the case of a salt of a polybasic acid, a mixed salt, e.g. a sodium potassium salt, can be employed. 7 The anion catalyst is preferably an anion of a carboxylic acid. The carboxylic acid can be an aliphatic, aromatic heterocyclic or alicyclic carboxylic acid. The carboxylic acid can contain one or more carboxyl groups. Where 10 there is more than one carboxyl group, one is preferably neutralized but the others may or may not be. Where there is more than one carboxyl group, a mixed salt, e.g. a sodium potassium salt, can be employed. The carboxylic acid preferably contains only carbon, hydrogen and oxygen atoms.
Especially preferred for convenience, availability and high , yield it results in ~s (a)~a straight chain alkanoic acid of 1-6 carbon atoms, which alkanoic acid is optionally substituted ;~ ~; by one or more groups selected from carboxyl and hydroxy groups, or (b) benzoic acid substituted by one or more groups selected from carboxyl and hydroxy groups.
The PKa of the acid whose anion may be employed : . ~
is usually in the range 2.0-6.5, preferably 2.8-5.7.
Particularly preferred specific salts are sodium acetate, disodium hydrogen citrate, sodium hydrogen phthalate or sodium hydrogen adipate.
A mixture of catalysts can be employed.

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The direct hydrolysis occurs at a pH of at least 2. For maximum yield, the pH is preferably 2.8-6Ø The hydrolysis produces hydrohalic acid HX, which can lower the pH below these lower limits. For optimum yield it is preferred to maintain the pH above these lower limits during the hydrolysis. This can be done by employing catalyst in salt form as appropriate, e.g. as sodium salt, to raise the pH over what it would otherwise be, or by admixing alkali. The alkali can be any convenient alkali, such as alkali metal hydroxide, carbonate or bicarbonate, e.g. sodium carbonate, but preferably sodium hydroxide. Preferably the pH is maintained at 2.8-6.0 throughout the hydrolysis.
Although we are not bound by this theory, it seems that when anion is used as catalyst, the hydrolysis may be -~
considered in terms of one catalyst anion displacing each halogen atom X on the 2,2,6,6-tetrahalocyclohexanone compound of formula I~ and then each catalyst anion being itself ~;-displaced by an HO ion from water, rearrangement occurring to result in the pyrogallol compound of formula I. It can be seen that this is anaiogous to the indirect hydrolysis mentioned above in which the tetrahalocyclohexanone compound is reacted with a metal alkoxide and the product is acid h~drolysed;

: ~ . .
there an alkoxide ion is the anion to displace each X atom, and the~displacement of the alkoxide ion occurs ln a separate stage.
When an anion is used as catalyst and the anion is ~`~
that oE a simple salt, the amount of cataly~t is preferably at least '"

~ .:
, :: :

,''~

~ l~6~5;Z1 4 anions per molcule of tetrahalocyclohexanone. Better yields are generally obtained using 6 lO of the catalyst anion, than using 4 of the catalyst anions, per molecule of tetrahalocyclo-hexanone. Generally, no better yield is obtained usiny 16 of the catalyst anions than using 8 of the catalyst anions, per molecule of tetrahalocyclohexanone.
When an anion is used as catalyst and the anion is that of a cation exchange resin, the amount of catalyst is preferably at least 4 equivalents, especially 6~10 equivalents, of anion per mole of tetrahalocyclohexanone, generally no better yield being obtained using 16 rather than 8 equivalents of anion per mole of tetrahalocyclohexanone.
When a base is used as catalyst, it is thought~
though we are not bound by this theory, that one equivalent of base reacts with one equivalent of hydrohalic acid produced in the hydrolysis. When a base is used as catalyst, the amount of catalyst is preferably at least 4 equivalents of base per mole of tetrahalocyclohexanone.
~- When the direct hydrolysis is used, an organic ; !
liquid, e.g. methanol or ethanol, may be employed in the reaction~mixture to give a system which is initially of one phase rather than two phases.
The present hydrolysis is preferably conducted in solution. At least the theoretical quantity of water to e~fect the hydrolysis must be e~ployed, and when direct hydrolysis is employed, the :

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solvent is preferably water in excess of that required for hydrolysis. When direct hydrolysis is employed, preferably the whole of any catalyst is in solution.

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When the alkoxide route mentioned above is employed, the reaction with the alkoxide is generally conducted in the presence as solvent of the alkanol from which the alkoxide is derived, and the subsequent acid hydrolysis may be conducted in the presence as solvent of water in excess of that required for hydrolysis.
Preferably the hydrolysis employs 0.3 ml - 1 litre of water per gram of tetrahalocyclohexanone compound.
The hydrolysis may for example be conducted at a -~
temperature of 0-250C e.g. 0-120C. rrhe reaction mixture is usually heated. In a preferred embodiment, particularly when direct hydrolysis is employed, the temperature is 60-140C.
Preferably direct hydrolysis is conducted under reflux.
The hydrolysis may be conducted under a pressure which is above, at, or~below atmospheric pressure. The pressure may for instance be 0.1-15 atmospheres, convenlently ~; ~20 atmospheric pressure.
The pyrogallol compound and its salts absorb oxygen when hot and the salts absorb oxygen even at ambient temperature.
Accordingly, exaessive heating of them should be avoided and it may~be~desirable in some instances to conduct the hydrolysis under an in~ert atmosphere, e.g. an atmosphere of nitrogen or carbon dioxlde.
; The product can be isolated and purified in conventional~ways.
:

:

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In the process of the present invention, the compounds of formula III, employed as starting materials, are either known compounds, or may be prepared by method~ well known to tho~e skilled in organic chemical synthesis for the preparation of analogous compounds~
The cataly~t for the procluction of 2,2,6,6-tetra- ~' chlorocyclohexanone or 2,2,6,6~tetrabromocyclohexanone enables reaction to be carried out conveniently and in high yield.
The catalyst is particularly useful when the desired product is then to be hydrolysed to pyrogallol.
A catalytic iamount of the catalyst must be employed.
Generally, the weight of catalyst is at least O.l~, preferably from 0.5 to 12~, of ths weight of the cyclohexanone compound.
The process is of particu1ar interest for the production of 2,2,6,6-tetrarhlorocyclohexanone, so that the halogen involved is chlorine rather than bromine and Y represents an atom of hydxogen or chlorine rather than an atom o~ hydrogen or bromiDe.
The cyclohexanvne compound is pre~erably cyclohexa- -20~ ne~itse1~, though an intermediately halogenated compound c~n be employed. For instance7 to producs 2~2,6~6-tetrachloro-cyclohexanone oDe clan st~rt from 2,2,6-trichlorocyclohexanone.
. ~ The reaction is preferably ~o~duated in the presence o~ a ~ :

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solvent. Suitable solvents include saturated chlorinated hydrocarbons (e.g. aliphatic hydrocarbons containing 1 or 2 carbon atoms and 2-4 chlorine atoms, such as carbon tetra-chloride, methylene dichloride or tetrachloroethanes), saturated hydrocarbons (e.g. those containing 5-10 carbon atoms such as pentane, hexane t cyclohexane, octane or decane) or saturated carboxylic acids (e.g. saturated aliphatic carboxylic acids containing 2-5 carbon atoms, such as acetic acid, propionic acid or butanoic acid). In the production of ]0 2,2,6,6-tetrachlorocyclohexanone, 2,2,6-trichlorocyclohexanone may be employed as solvent. Preferably, however, the solvent is molten desired product, e.g. 2,2,6,6-tetrachlorocyclo-hexanone, itself. A mixture of solvents can be employed but this is not preferred.
In a preferred mode of operation~ the halogen and cyclohexanone compound are fed to a reaction zone containing a solvent and the catalyst.
~ The reaction is usually conducted at a temperature within the ran~e 60-160C, preferably 75-110C, e.g. 80-110C.
The reaction temperature is preferably below the boiling point of the solvent if a solvent is employed. When molten 2,2,6,6-tetrachlorocyclohexanone is employed as solvent, the reaction temperature is its melting point as altered by the other materials present. The melting point of pure 2 r 2,6,6-tetra-chlorocyclohexanone is 82-83C.
The xeaction is preferably carried out under substantially .

~ ' . ' .:
~ . .;

:~ , ., ., , , , . , , " , , , , ~ , , .

6~
anhydrous conditions i.e. less than 1%, preferably less than 0.5~, by weight of water being present based on the weight of the cyclohexanone compound.
The overall amount of chlorine or bromine employed is normally sufficient to convert a].l the cyclohexanone compound to desired product. When the reaction is conducted by feeding the halogen and cyclohexanone compound to a reaction zone containing a solvent and the catalyst, it is preferred, in order to minimise side reactions, that the amount of the halogen in contact with the cyclohexanone in the reaction zone be at all times at least the stoichiometric amount required to convert the cyclohexanone compound present to the desired product. For instance, starting from cyclohexanone there is preferably at least 4 moles of halogen fed per mole of cyclohexanone fed; desirably, 4-6 moles of halogen are fed while each mole of cyclohexanone is fed.
Again when the reaction is conducted by feeding the : halogen and cyclohexanone compound to a reaction zone containing a solvent and the catalyst, the hourly rate of feed 20 ~:of the cyclohexanone compound to the zone is usually at no ; time greater than 1/2, e.~. greater than 1/3, the weight of :
the solvent at that time. If one starts with a particular ~.
weight, W, of solvent, the initial hourly feed rate of cyclohexanone compound can thereore be W/2. I the reaction proceeds to produce desired product to act as further solvent, the total weight of solvent increases and hence the hourly fecd rate:of cyclohexanone compound can be increased while , : ~

.

Zl s~ill keeping it no more than l/2 the weiyht of ~olvent. Convanien-tly, however, a constant fead rate i.~ employed.
To ensure maximum conversion to the de~ired product (particular-ly 2,2,676-te~rachlorocyclohexanone), it i8 preferred to continue the halogen feed after the end of thle cyclohexanone compound feedO
Preferably, the halogen feed i8 continued until the weight of 2,2,6-trihalocycl~hexanone (partiularly 2~2J6 trichlorocyclohexanone) ~:t'~, i~ les8 than 5~, e~pecially les3 than 1%, of the totaL weight of 2,2,6-trihalocyclohaxanone and 2,2,6,6-tetrahalocyclohexanone. It is preferred to continue the halogen feed for at least 1/4 hour, for instance for 1/4-3 hours, e.g~ for 1/2-3 hoursJ after the end of the cyclohexanone compound feed.
The desired product can be separated in ¢onventional ways.
useæ for the invention ara illustrated by the following Examples in which parts and percentages ara by weiyhtO
: Exampl~ ~1 , .
: . .;
:~ A mixture o~ 2,2J6,6-te rachlorocyclohexanone (100 part3) and :

~:~ wat~r~532 p~rts) was heated to 60C and morpholine (149 part~) ,:
added dropwise over a period of 14 mins. The mixture wa~ :' 20~: maintained at 60 for a further 4 mins,J than cooled and filtared.
The filtrat~ was acidified by addition of 21 part~ of concentrated hydrochloric acid ~301utionJ then continuou~ly ~xtracted with :~ ~ther. A~t~r drying over MgSO4, khe extract wa~ evaporatad to giv~ 21 parts o~ tar, shown to contain 6 parts (11~2~ yield) of . .
~; ~ pyro~allol by GLC (~5 liquid chromatography) a~ter acetylationO

;

45'~
Example 2 _ _ Under a blanket of nitrogen were mixed 2,2,6,6-tetrachlorocyclohexanone (100 parts), sodium acetate (424 parts) and water (1,059 parts), and the mixture refluxed for 10 minutes. The mixture was then cooled to 50C when sodiurn bicarbonate (318 parts) was added giving severe foaming. The mixture was then extracted continuously with ether, the extract dried over magnesium sulphate and evaporated to give a residue (39 parts). The residuQ was triturated with chloroform (39 parts) to give after filtering and drying in air 15.2 parts of pyrogallol (28.5~ yield) as a tan solid, m.pt. 130.5 - 133.5C.

Example 3 Under a blanket of nitrogen were mixed 2,2,6,6-tetrachlorocyclohexanone (100 parts), disodium oxalate (456 parts) and water ' ~ ' , ' .:

~ , :

.

1(1 ~4~i2~
(1,064 parts~, and the mixture refluxed for two hours. The mixture was then extracted continuously with ether and dried over sodium sulphate. After filtering, the extract was evaporated to give 52.2 parts of resldue shown to contain pyrogallol (24.5 parts, 46% yield) by GLC after conversion to the triacetate.

Example 4 _ . .
2,2,6,6-Tetrachlorocyclohexanone (2.36g, O.OlM) was added to 35 mls of a stirred 27% sodium methoxide solution (0.17M) under nitrogen at 24~C. The temperature of the mixture rose and was held at 45C by external cooling. When the exotherm had finished, the mixture was cooled in ice and concentrated hydrochloric acid (17 mls) and water (28mls) were added. The methanol was distilled from the reaction mixture ~ -under nitrogen, and the resultant aqueous solution was continuously extracted with ether. The ether extract was dried (~gSO4) and the ether removed under vacuum to give a residue (0.85g) analysing as 18% pyrogallol. This represents a ~ pyrogallol~yield of 12.2%.

;~ 20~Example 5 ;
2,2,6,6-Tetrachlorocyclohexanone (4.72g, 0.02M) was added~to a solution of disodium hydrogen citrate (0.16M) made , by~adding with cooling sodium hydroxide (12.8g) to a solution of cltric acid monohydrate (33.6g) in water (50 mls). The mixture was stirred and heated to reflux. The reaction mixture ~ ;
was sampled at intervals and analysed for free chloride until the~samples showed the reaction was complete. The total reflux , ~ ; ;time was ~:

.
~ 17 -4 hours. The reaction mixture was continuously extracted with ether. The ether extract was dried (MgS0~), filtered and the ether removed to give a residue (2.74g) analysing as 77.5%
pyrogallol. The pyrogallol yield is 84.4%.

Example 6.
. . _ 2~2,6,6-Tetrachlorocyclohexanone (4.72g, 0.02M) was added to a mixture of phthalic acid (26.5g, 0.16M) in water (75 mls) to which sodium hydroxide (6.4~, 0.16M) had been added.
The mixture was heated to reflux for 1 1/2 hours. Sodium hydroxide solution (5 mls of 5N) was added over 5 minutes and the mixture was heated at reflux for a further 2 1/2 hours. A
sample was analysed for free chloride and this indicated the reaction was complete. Concentrated hydrochloric acid (13 mls) was added at 90C. The reaction mixture was cooled to 5C and the phthalic acid was removed by filtration. The p~ of the filtrate was adjusted to 3.5 and it was continuously extracted -~
with ether. The ether extract was dried (Na2S04), filtered and the ether removed to give crude product (3.04g) which contained 2~02g of pyrogallol. This represents a pyrogallol yield of 80%.

Exam ~e 7 Glacial acetic acid (9.6g, 0.16M) was dissolved in distilled water and the pH was adjusted to 4.7 with lON sodium hydroxide solution. The volume of the solution was adjusted to 55 mls by dilution with distilled water. 2,2,6,6-Tetra-chlorocyclohexanone t4.72g, 0.02M) was added and the mixture wa~ heated to reflux.

.

645;2~L
The pH of the reaction mixture was kept at 4.7 by the addition of 5N sodium hydroxide solution. Samples were taken inter-mittently and analysed for free chloride to determine the end of reaction. The resulting aqueous solution was continuously extracted with ether. The ether extract was dried (Na2SO4), filtered and the ether removed to give crude product (3.5g) which contained 1.46g of pyrogallol. The pyrogallol yield was 58%.

Example 8 Amberlite IRC 50 ion exchange resin in the sodium form (16.8g, dry) was suspended in distilled water (50 mls). -2,2,6,6-Tetrachlorocyclohexanone (4.72g, 0.02M) was added and the mixture was heated to reflux for l l/2 hours by which time the pH had fallen from 6.2 to 1.7. The pH was adjusted to 3.8 and reflux was continued for a further 4 hours during which -the pH was kept between 2 and 4 by the addition of 5N sodium -hydroxide solution. A chloride analysis indicated 92%
completion of the hydrolysis. The resin was filtered off and ; ~ the reaction mixture was continuously extracted with ether.
The ether extract was dried, filtered, and the ether removed to leave a brown oil (1.2g). This analysed as 19.6% pyrogallol, :: .
;representing a 9.3% pyrogallol yield. ;

Exam~le 9 :: :
; 2,2,6,6~Tetrachlorocyclohexanone (4.72g, 0.02M) was added ;~ to distilled water (50 mls) and the pH was adjusted to 5.0 with ;~ 5N~sodium hydroxide solution. The mixture was stirred and : ~ . :
:,: ~

09/1~/4S
1al6~5LS~l heated to rcflux and the pll was kept at S.0 by the addition of sodium hydroxidc solution. The mlxture was samplcd at inte~als and analyscd ror frce chloride until the rcaction was complete.
~he reaction mixture was ether extracted and the e~ler extract S was dried ~Na~S04)~ ~iltered and the ether distilled of~ to give a brown oil (1.3g)~ ~lis contained 0.03 g of pyrogallol which represents a 1.2~ yield.
Exam~le 10 ~ , .
Following Example 9 but maintaining the pll at 3.0 gave a

3.7~ yield o pyrogallol.
~ ' ' .
Following rxample S but using 0.02 moles of 2,2,636-tetra-bromocyclohexanone instead o~ the tetrachlorocyclohexanone gave a 44~ yield o pyrogallol.
~
A suspension o 2,2,6,6-tetrachlorocyclohexanone ~4.72g, 0.02M~ was heated under reflux with an aqueous solution/suspension of the catalyst compound listed below (O.lSM; in the case of the Anberlite IRC 50, 16.0g of dry resin were employed) in 50 mls of 0 water. The mixture was sampled at intervals and analysed or free~chloride to determine the end point of ~le reaction. The ; aqueous reaction mixture was then ~ilt~red if necessary and extracted continuousl~ Wi~l ether. ~le e~her extrac~ was dried NazSO4)~ filtered and ~he ether removed to give ~le crude p~rogallol. ~liS was analysed to determine the yield.

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Bx.~ml~]e ~ ound Yie]d o~ Pyroga.l~o~
12 Trisodi~n Citrate 25.5 13 Sodium Dihydrogen Citrate 31.0 14 Sodium ~lloroacctate 31.0 So~iwn IIydrogcn Ma].ate 71.0 16 Disodium ~I.alate 52.0 17 Potassi-un l-}yclrogen Phtllalate 75.0 18 ~moniunlllydrogen Phthalate52.0 19 Sodium ~Iy~rogen Isophthalate 59.8 Sodium ~ydrogen l'artrate 58,0 - 21 Disodiwn Tartrate 60.5 22 Disoclium Oxalate 44.0 . 23 Sodium o-Ni~robenzoate 35.1 -~ . 24 Sodium Benzoate 49.5 15 25 ~ Sodium Lactate 6~15 26 : Sodium Propionate: 42.~
27 : Sodium Glycolate 57.0 : 2S: Disodi~n Malona~e 27.0 29 : Sodium Formate ~ 20.8 0~ ~ ~30 ~ Sod:iwn Salicylate 29.0 31: ~ Sodiwn ~ydrogen ~ipate 82~0 32~: ~Disodiwn ~dipate 4600 33 dnberlite IRC 50 ~l forin 17.0 34 Disocli~Im Hydrogen Phosphate 22.6 25~35 ; Sodi~n Dihydrog~n Phosphate32.5 ; ~ - 21 -~6~5ZJ.
Example Catalys CompoundYie;ld of Pyroga 36 Monosodium Borate 7.0 37 Potassium Fluoride 16.0 38 Ethylene Diamine Tetraacetic 49.0 acid, Disodium Salt 39 Sodium Hydrogen Fumarate 53 Disodium Fumarate 58 41 Sodium Hydrogen 1,2,3,6-rretra 62 hydrophthalate 42 Sodium ~ydrogen Maleate34 lO43 Sodium Pivalate 11 44 Dipotassium Oxalate 71 Sodium Picolinate 6 46 Sodium Furoate l9 47 Disodium Di Hydrogen 47 Pyrophosphate 48 Sodium Hydrogen succinate 76 49 Sodium Sulphamate 13 Sodium hydrogen phosphite 18 51 Dlmethyl oxalate 25 52 Sodium gluconate 67 , Exam ~e 53 ::
2,2,6,6~Tetrachlorocyclohexanone (4072y, 0.02M~ was added to a solution of morpholine citrate made by adding with cooling morpholine (24.6 mls 0.283 moles) to a solution of citric acid monohydrate (33.6g, 0.16 M) in water (50 mls).
The mixture was stirred and heated to reflux. The reaction mixture was sampled ~ 22 -: ~ `:: :
:: :

,~;36~S2~
. . , at intervals and analysed for free chloride until th~ sampl~s showed the reaction wa~ complete. I~e total r flux time wa~
3 hours. The reaction mixture wias continuously extracted with ether. The ether extract wa~ dried (MgS04), filtered and the ether removed to give a residue (5.4g) analysing as 33.6%
pyrogallol. The pyrogallol yield i~ 71.9~. ~
t : ' 2,2,6,6-Tetrachloro-4-methylcyclohexanone (5.0g, 0.02M) wa~ added to a solution of sodium hydrogen phthalate ~ 10 (30.1g~ 0.16M) in 50 mls of water. The mixture was heated at '~' re~lux and ~ampled at intervals ~or free chloride determination.
;:
When the reac ion was complete the mixture waa cooled, filtered, .
- ether~extracted and the ether removed to give a crude product~
3.8g, which contained 1,2,3~trihydroxy~5-methylben2ene (methyl 15~ pyrogallol). (1.26g). mi~ represents a 45% yield~

45g of 2,2,6~6~tetrachlorocyclohexanone (TCC~) and Sg of txibutyl phoaphLne were charged to a 500 ml flask ~itted with~a mechanical stirrer, a thermometer, a water conden~er and a~chlorine inlet tube having a ~intex outlet to the bottom of the ~la~k~ The fla~k wa~ heated~ and the melt at 85-90C
was ~wept with nitrogen fox 10 minute~ At 95-105C, 276g o~
ahlorine~and 66g o~ cyclohexanone wexe ~harged to the ~lask continuously over 6~7 h~urs. The mole ratio o~ chlorine to ~ cyclohexanone waa kept at 5.8 throughout the addition.
Chlorine was ~hen added continuou~ly at the ~ame rate as it ~ wa~ be~ore fox l-lf2 hours 7while maintaining the ~ame J,~ temperature- 375 ml n-hexane were added to the reaction mixtureJ which was then h~a~e~ to give a clear solution.

,, ,.. , ; , , ~ , . . . . ... . . . ..

: : :

L636~ 2:~L
Cooling o:E th~ ~olution to 5C precipitated crystals o~ TCClH, which a:~ter :f~iltration iand drying colltained 137. 0g ; (86.5% yield) o~ freshly ormed TCCE (i~.e. the TC~H over and above that charged initially to the ~lasX ) O Analysis showed that the result:ant ~rCCFI was 9g% pure..

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for preparing 2,2,6,6-tetrachlorocyclo-hexanone or 2,2,6,6-tetrabromocyclohexanone, which process comprises reacting in the liquid phaae, in the case of the production of 2,2,6,6-tetrachlorocyclohaxanone, chlorine, and in the case of the production of 2,2,6,6-tetrabromocyclohexanone, bromine, with a cyclohexanone compound of formula where each Y is the same or different and represents, in the case of the production of 2,2,6,6-tetrachlorocyclohexanone, an atom of hydrogen or chlorine, and in the case of the production of 2,2,6,6-tetrabromocyclohexanone, an atom of hydrogen or bromine, in the presence of a catalyst selected from tributyl phosphine or a salt thereof.

2. A process according to claim 1 wherein the cyclo-hexanone compound is cyclohexanone itself.

3. A process according to claim 1 wherein 2,2,6,6-tetra-chlorocydohexanone is prepared.

4. A process according to claim 3 wherein the reaction is conducted in molten 2,2,6,6-tetrachlorocyclohexanone as solvent.

5. A process according to claim 3 wherein the reaction is conducted at a temperature of 75-110°C.

6. A process according to claim 3 wherein the reaction is carried out under substantially anhydrous conditions.

7. A process according to claim 3 wherein the chlorine and cyclohexanone compound are fed to a reaction zone containing a solvent and the catalyst.

8. A process according to claim 7 wherein the amount of chlorine in contact with the cyclohexanone compound is at all times at least the stoichiometric amount required to convert the cyclohexanone compound present to 2,2,6,6-tetrachlorocyclo-hexanone.

9. A process according to claim 1 wherein the 2,2,6,6-tetrachlorocyclohexanone prepared is then hydrolysed to produce pyrogallol or a salt thereof.