[CONTRIBTJTION FROM
THE LABORATORY OF ORGANICCHEMISTRY OF THE UNIVERSITY OF IOWA]
STATE
THE ACTION OF NITROUS ACID ON CERTAIN HALOGENATED SUBSTITUTION PRODUCTS OF 2,5-,3,4- AND 3,5DIMETHYLPHENOLS L. CHAS. RAIFORD
AND
DONALD W. KAISER
Received June 19, 1989
Zincke and collaborators1 proved that when a brominated phenol or cresol is treated with nitrous acid, bromine or a hydrogen atom in a favorable position as respects hydroxyl may be replaced by the nitro group. Raiford and others2have shown that when both ortho and para positions are occupied by bromine isomeric 0- and p-mononitrohalogenated derivatives may be formed by this treatment in a single experiment. Chlorine is not replaceable by the nitro group under these conditions. Later Raiford and Scott3 found that sym-tribromo-m-xylenol gives a mixture of 2,6dibromo-4-nitro-m-xylenoland 2 ,6-dibromo-m-xyloquinone. In view of the fact that bromine was replaced from position 4 only, it was desired to obtain for comparison the isomeric 2-nitro-4,6-dibromo-m-xylenol, and also to examine the behavior of the tribromo substitution products of other xylenols. Nitration of 2,5-dimethyl-3,4,6-tribr~mophenol~ with nitrous acid gave a mononitrodibromo compound in which halogen was replaced from position 4 (OH=l). Treatment of this product with fuming nitric acid eliminated the nitro group and gave 3 ,6-dibromo-p-xyloquinone. Further proof that the compound in question was a 4-nitrophenol was obtained by study of the acetyl-benzoyl derivatives of its reduction product. Int,roduction of the required acyl radicals in both possible orders led to isomeric mixed diacyl derivatives. The relationships are indicated in Figure 1. 2,5,6-Tribromo-3,4-dimethylphen~l~ was next tested. Treatment of this with nitrous acid as directed by Zincke gave an o-nitrodibromo compound. The relative positions of the hydroxyl and nitro radicals were determined by a study of the reduction product. The aminophenol obtained here gave but one mixed acetyl-benzoyl derivative, regardless of ZINCKE, J . prakt. Chem., [2], 61, 601 (1900); DAHMER, Ann., 333, 353 (1904) 66,2131 (1933). 3 RAIFORD AND SCOTT, J. ORQ.CHEM.,2, 221 (1937). 4 JACOBSEN, Ber., 11, 27 (1878). 1
* RAIFORD AND MILLER, J . Am. Chem. Soc., 565
556
L. CHAS. RAIFORD AND DONALD W. KAISER
the orde? of introduction of the acyl groups, and in this product the heavier of these radicals was found attached to nitrogenas Although the facts cited above showed that an ortho aminophenol was involved, it was still a question whether the amino group occupied position 2 or 6. An attempt to decide between these positions was made by trying to brominate 3,4-dimethyl-6-nitrophenol. To obtain this material the required xylenol was nitrated in accordance with Diepolder's directionsn6 By fractional crystallization of the product from alcohol the mon-
II
NO*
0
OCOCH,
Br CHaOCJrNHCOCHa
cJ@
Br
c--
NHCOCHa
OCOCHa
Isomers
BACH~ Br/\CH8 CH*UBr
NHCOCHs
OH
+-
NHCOCsHs
CH8()Br NHCOCsHs
onitro compound was isolated in small yellow plates that had the melting point recorded in the literature. This product was brominated, but only 6 This behavior has previously been shown by RAIFORD AND OTHERS [ J . Am. Chem. SOL,48, 483 (1926)l t o be characteristic of o-aminophenol derivatives. By nitration of 3,4-dimethylphenol DIEPOLD~R [Ber., 42, 2916 (1909)l obtained the 6-nitro compound, m.p., 87", and the 2,6-dinitro derivative, m.p., 127". No directions for separation and purification of these products were given except the statement that the mononitro compound was isolated by crystallization from alcohol, and that both products are volatile with steam, but a t different rates.
557
ACTION OF NITROUS ACID ON HALOQENATED PRODUCTS
one halogen atom could be introduced. Treatment of the reduction product with bromine did not permit further halogenation. Nevertheless, in the nitrodibromo compound in question the nitro group will be recorded as occupying position 6, since that is the most likely place in terms of the orientation rules. The relationships of these derivatives are indicated in Figure 2. It was indicated above that when sym-tribromo-m-xylenol was nitrated the 4-nitro compound only was produced. On this account it was of in-
0
FIGURB 2
Br@
N z OH o r
Br
CHt
CHI
rJN f
I
OH
CH,
CHa
CH:
I OCOCHt
CH:
C&HsCO'.:(>".'. OCOGHs
-
c-
CHs
Br\
CH:
C H & O N OCOCHa Hor c -
B
CHa
CHr
C H a C O NOH Hor
Br()NOz OH
--+
-_3
CHs
or
CHa CHs
CHs
I(
/
OH
terest to obtain for comparison the isomeric 2-nitro derivative. To do this an indirect method was used. 2-Kitro-3, 5dimethylpheno17 was brominated as described in the experimental part hereafter. The product was characterized by a study of its methyl ether, and particularly by the behavior of its reduction product. This aminophenol gave but one acetylbenzoyl derivative, although the acyls were introduced in both possible 7 This was prepared by directions recorded by AUWERSAND BORSCHE [Ber., 48, 1714 (1915)].
558
L. CHAS. RAIFORD AND DONALD W. KAISER
orders, which characterized it as an ortho compound. Figure 3 shows the relations of the compounds involved. In previous work in this field Raiford and MillerBfound that in the compounds they studied the chlorine atom could not be replaced by the nitro group when the Zincke method is used. In view, however, of the observations of Raifords on the behavior of 2,4,6-trichloro-m-cresol, and of Raiford and Scott3 in their study of 2 ,4,6-tribromo-s~mm-xylenol,in the latter of which nitration gave rise to a nitro compound and a quinone, the corresponding trichloro-mxylenol FIQURE 3
Br@ OHZ c O c H 8
+CHa
I
B()"COOCOCHa CHa
CHa
c -
CHs
Br
B r OH o H s
CHa Br
CHa
CHa Br
\
-
B
OCOCsHr r
/i CHI
CHI
I/
OCOCHs
OH
Br
Br
was examined. With this fuming nitric acid gave a quinone but no nitro compound. When formed through the action of nitrous acid the quinone immediately combined with two molecular proportions of the unchanged phenol and was isolated as a molecular compound.10 Attempts to convert RAIFORD AND MILLER, J. Am. Chem. SOC.,66,2125 (1933). RAIFORD, A m . Chem. J . , 46, 425 (1911). 10 MEYER[Ber., 42, 1149 (1909)l AND WOOLLETT AND OTHERS [J.Am. Chem. SOC., 69, 862 (1937)l have referred to such products as phenoquinones. 8
p
559
ACTION OF NITROUS ACID ON EALOOBNATED PRODUCTS
the quinone into a monoxime by treatment with hydroxylamine gave the corresponding quinhydrone. When a mixture of stannous chloride and hydrochloric acid was used as a reducing agent, the hydroquinone was obtained. The relations involved in this case are shown in Figure 4. EXPERIMENTAL
~,b-Dimethyl-S,d-dibromo-~-nitrophenol.-Two hundred and fifty grams of 2,5dimethyl-3,4,0-tribromopheno11* was dissolved as far as possible in a mixture of 3 liters of acetic acid and 200 cc. of dioxane*, cooled to 7-10", 12 g. of sodium nitrite was added with stirring during a period of two hours, the mixture was allowed t o stand overnight and was then poured with rapid stirring into about 18 liters of water t o precipitate the product. A yield of 81% was obtained. Crystallization from
{?
,
CHavCHs
'0'
CHI
FIGURE 4
0
Fuming HONOa
,
CHs
CHa
c1
OH
0
d0
0
*2 CH,
CHI
0 cl()a CHa
.
cl()
CHa CHs
CHa
Cl
ligroin (b.p. 60-70") containing about 10% of benzene gave large yellow needles that melted at 152-153" with decomposition'*. Anal. Calc'd for CaH,BrtNOa: Br, 49.23. Found: Br, 48.99. ~,6-DimethyE-S16-dibromoJ-nitrophenyl methyl ether.-This was prepared for 11 This was obtained in quantitative yield by bromination of 2,5-dimethylphenoI as directed by AUWERSAND ERCKLENTZ [Ann., S02,114 (1898)l. * Dioxane increased the solubility of the halogenated xylenol and lowered the freezing point of acetic acid. When a Zincke nitration is conducted a t 14" much of the acetic acid may solidify. 12 ZINCKEAND BREITWIESER [Ber., 44, 182 (19ll)l reported 154" for this product which they obtained from the corresponding chinitrol, and which they said was colorless. They reported no yield.
560
L. CHAB. RAIFORD AND DONALD W. RAISER
further identification of the above nitro compound. Ten g. of the latter was dissolved in 75 co. of methanol containing 2 g. of potassium hydroxide, 3 g. of dimethyl sulfate was slowly added, the mixture was refluxed for two hours, and then poured into a large volume of ice water containing caustic potash. The colorless precipitate was obtained in 58y0 yield, and crystallization of it from methanol gave slender needles that melted a t 85-86". Anal. Calc'd for CpHpBrzNOs: Br, 47.17. Found: Br, 47.01. .%?,b-Dimethyl-3, 6-dibromoJ-nitrophenyl acetate.-Five grams of the required nitro compound was warmed with 1 g. of anhydrous sodium acetate and 5 cc. of acetic anhydride, the cooled mass was extracted with water, and the residue was crystallized from dilute acetic acid. Small needles that melted at 114115" were obtainedt. Anal. Calc'd for C~OH~BrzNOI: Br, 43.59. Found: Br, 43.42. b,6-Dibromo-p-xyloquinone.-Ten grams of the above-described nitrophenol was sprinkled into 50 cc. of fuming nitric acid that had previously been cooled to 0", the mixture was allowed to come to room temperature, the red solution obtained was heated on a steam bath for five minutes after red fumes began to appear, and the liquid poured into ice water. The solid obtained was crystallized from carbon tetrachloride from which it separated in small yellow scales that melted a t 185-186'. The yield of purified material was 58%15. A d . Calc'd for CsHsBr202: Br, 54.42. Found: Br, 54.45. Hydrochloride of S,b-dimethylS, 6-dibromo-~-aminoph.enol.-Fifty grams of the required nitro compound was reduced with stannous chloride and hydrochloric acid as directed by Raiford and ColbertI4and the colorless amorphous product was washed with hydrochloric acid and then with ether. The yield was 72%. The compound decomposed a t about 225". Anal. Calc'd for CsHloBrzCINO: Hal., 58.92. Found: Hal., 59.10. 8,6-DimethyZ-b,6-dibromo-&aminophenol.-A portion of the required hydrochloride was suspended in water, treated with ammonium carbonate solution, and the residue was crystallized from methanol. The pale-brown plates obtained melted with decomposition a t 187-188". Zincke and Breitwieser (loc. cit.) reported 186-188", but recorded no analyses. Anal. Calc'd for CsHoBrlNO: Br, 54.23. Found: Br, 54.12. The above aminophenol waa further characterized by a study of its acetyl-benzoyl derivatives, for which analytical data and other properties are given in Table I. Nitration of S,4-dimethyZphenol.-To$ solution of 10 g. of the phenol in 100 cc. of glacial acetic acid in a suitable flask cooled in t a p water, there was added, as rapidly as possible, a mixture of 15 cc. of concentrated nitric acid and 50 cc. of acetic acid. The solution turned red instantly, and after one minute was poured slowly into five volumes of ice water that was being stirred rapidly. The yellow oil that separated became solid in about half an hour. By fractional crystallization from alcohol the mononitro compound was obtained in 19% yield of small yellow plates that melted a t 86-87'16; while only 8% of the dinitro product was secured. This melted a t 126-
t ZINCKE AND BREITWIESER(loc. cit.) reported 116" but did not analyze their product. 18 This product should be identical with that of m.p. 184",obtained by CARSTANJEN [ J . prakt. Chem., [2],23, 434 (1881)l by bromination of p-xyloquinone. AUWERS AND RAPP[Ann., 302, 166 (1898)]found 185-186". Neither worker recorded a yield. 14 RAIFORD AND COLBERT, J . Am. Chem. Soc., 47, 1457 (1925). 16 DIEPOLDER, reference 6, found 87".
ACTION OF NITROUS ACID ON HALOGENATED PRODUCTS
R%%%F?i-? . . . . . . ... ... ... ... ... ... .
.
.
.
.
.
561
562
L. CHAS. RAIFORD AND DONALD W. KAISER
127', as recorded by Nolting and Pick". By steam-distillation of the crude nitration product, and crystallization of the volatile material from ligroin (60-70"), the mononitro compound was obtained in 38% yield. Bromination of 9,4-dimethyl-6-nitropheml.-Ten grams of the nitro compound was dissolved in 40 cc. of acetic acid, 0.5 g. of iron powder was added, and the mixture was heated on the steam bath while a solution of 21 g. of bromine in 10 cc. of acetic acid was slowly added from a t a p funnel. The liquid was heated for three hours and then poured into ice water containing sodium bisulfite. Crystallization of the product from methanol and then from ligroin (60-70") gave slender yellow needles that melted a t 74-75'. The yield was 82%. In a second experiment 2 g. of the nitro compound dissolved in 10 cc. of carbon disulfide was treated with 3 cc. of bromine containing about 1% of aluminum bromide, the mixture was allowed to stand overnight, the solvent was distilled off, the dark oil was dissolved in caustic alkali solution, boiled with charcoal, the mixture was filtered and the filtrate was mixed with concentrated hydrochloric acid. Crystallization of the precipitate as explained above gave yellow needles that melted at 74-75'. The yield was 73%. In a third experiment the phenol was subjected to the action of bromine without solvent, but the product was identical with those mentioned above. Analysis indicated a monobromo compound. Anal. Calc'd for CaHaBrNOs: Br, 32.52. Found: Br, 32.60. Hydrochloride of I-bromo-~,4-dimethyl-6-amimphenol.-Fortygrams of the required nitro compound was reduced with a mixture of stannous chloride and hydrochloric acid, as previously explained. A yield of 74% was obtained. The product decomposed a t about 260". Anal. Calc'd for CaHllBrClNO: Hal., 45.74. Found: Hal., 45.88. I-Bromo-$,4-dimethyl-6-aminophenol.-This was obtained by treatment of an aqueous suspension of the required hydrochloride with ammonium carbonate solution until effervescence ceased. Crystallization of the residue from methyl alcohol gave pale pink plates that melted at 103-104'. Anal. Calc'd for CaHloBrNO: Br, 37.03. Found: Br, 37.17. %Bromo-$, 4-dimethyl-6-acetylaminophenyl acetate.-A mixture of 20 g. of the above aminohydrochloride, 8 g. of fused anhydrous sodium acetate and 25 g. of acetic anhydride was heated on a steam bath for one hour, the cooled mixture was extracted with water, and the residue was crystallized from alcohol. The material separated in masses of colorless fluffy needles that resembled cotton and melted a t 199-200". The yield was 88%. Anal. Calc'd for CI2HlrBrNOa: Br, 26.66. Found: Br, 26.72. Attempts t o introduce a second atom of bromine into this compound were unsuccessful. d , b , 6-Tribromo-~,~-dimethylphenol.-Jacobsenrecorded a melting point of 169", Auwers and Rapp found 171', while Crossly and Renouf17 reported 172-173' for a product which probably had the composition and structure indicated above. Auwers and Rapp alone indicated a method of preparation while neither of them gave analytical data for the product. In the present work 75 cc. of bromine (an excess) was allowed to drop slowly on 50 g. of Eastman's purest 3,4-dimethylphenol NBLTINQ AND PICK, Ber., 21, 3158 (1888). JACOBSEN, Br., 11,28 (1878); AUWBRSAND RAPP,Ann., 302, 160 (1898); CROSSLY AND RENOUF,J . Chem. Soc., 106, 177 (1914). 16
17
ACTION OF NITROUS ACID ON HALOGENATED PRODUCTS
563
contained in a dry 250 cc. flask with an outlet tube to convey hydrogen bromide t o a suitable trap. The mixture, which became liquid as the reaction progressed, but which solidified after all bromine had been added, was allowed to remain overnight, and was then treated with a concentrated solution of sodium acid sulfite. The solid was removed from the flask, and triturated with more sulfite solution; the mixture was filtered, and the residue was washed several times. A quantitative yield of colorless solid was obtained. Crystallization from alcohol gave lustrous needles that melted a t 173-174". Anal. Calc'd for C8H,Br10: Br, 66.85. Found: Br, 66.90. Nitration of B,6,6-tribromo-d,4-dimethylphenol.-Fifty grams of the abovedescribed crude tribromo compound was suspended in 400 cc. of acetic acid; the mixture was stirred continuously, while 20 g. of solid sodium nitrite was added during a period of about three hours. The starting material that caked on the walls of the beaker was dislodged frequently, and the lumps were broken u p with a heavy glass rod. The mixture was allowed to stand overnight and was then poured slowly into 5 volumes of ice water t h a t was being stirred rapidly. The product that separated gave, after two crystallizations from methanol, slender yellow needles that melted a t 168-169" with apparent decomposition. By working up the filtrates a yield of 61% of purified material was obtained. Anal. Calc'd for C8HrBr2N08:Br, 49.23. Found: Br, 49.23. ,9,6-Dibromo-9,4-dimethyl-6-nitrophenyl methyl ether.-Six grams of the abovedescribed nitro compound was dissolved in 50 cc. of methanol containing 1.2 g. of potassium hydroxide, the deep-red solution was gently refluxed while 2 g. of dimethyl sulfate was slowly added through the condenser, the mixture was heated for two hours and then was poured into ten volumes of ice water containing some alkali. Crystallization of the precipitate from methanol gave small, nearly colorless needles t h a t melted at 1OO-10lo. A yield of 67% was obtained. Anal. Calc'd for CDHoBrzNOs:Br, 47.19. Found: Br, 46.98. Hydrochloride of ,9,6-dibromo-d, 4-dimelhyl-6-aminophenol.-Forty grams of the above nitrophenol was reduced with stannous chloride as previously explained. The small colorless plates that separated were collected, washed with concentrated acid and with methanol. The yield was 87%. The product decomposed about 230" without melting. Anal. Calc'd for C8HloBr2C1NO:Hal., 58.92. Found: Hal., 59.02. B,6-Dibromo-d, 4-dimethyl-6-aminophenol.-A water suspension of the abovedescribed amino hydrochloride was treated with ammonium carbonate solution until effervescence ceased, and the residue was collected. Crystallization from methanol gave nearly colorless slender needles that decomposed a t 130-131". Anal. Calc'd for CsHoBrnNO: Br, 54.23. Found: Br, 54.04. This base was further characterized by the study of its acyl derivatives. Only one acetyl-benzoyl derivative could be obtained. Analytical data and other properties for this and related compounds are given in Table 11. I-Nitro-~,6-dimethyl-4,6-dibromophenol,-To a solution of 20 g. of the required nitrodimethyl phenol18 in 100 cc. of acetic acid held a t the temperature of the steam bath, there was slowly added 13 cc. of bromine diluted with 20 cc. of acid, and the 1s This product was obtained by nitration of the corresponding phenol as directed by AUWERSAND BORSCHE [Ber., 48, 1914 (1915)l. Along with it some of the isomeric 4-nitro compound was formed. The yield of the first was 16% and that of the second about 3.5%.
564
L. CHAS. RAIFORD AND DONALD W. KAISER
I :.. :.. :.. :.. : ..
ACTION OB NITROUS ACID ON HALOGENATED PRODUCTS
566
mixture was allowed t o stand overnight. The solid t h a t separated was collected, and washed with small portions of dilute methyl alcohol; the filtrate was poured into 5 volumes of water, and a small portion of solid was recovered. This was mixed with the original solid. A yield of 90% was obtained. Crystallization of the product from a1:ohol gave pale yellow needles that decomposed at 160-161". A mixture of this product and the isomeric 4-nitro compound, m.p., 172-173"18, decomposed a t about 148'. Anal. Calc'd for CsHrBrzNOa: Br, 49.23. Found: Br, 49.02. I-Nitro-t16-dimethyl-4, 6-dibromophenyl methyl ether.-Thirty-two grams of the required nitro compound was dissolved in 125 cc. of methanol and a solution of 6 g. of potassium hydroxide in 35 cc. of the same solvent was added. The deep-red solution was heated for two hours under reflux on a steam bath, and the mixture was poured into a large volume of ice-water containing caustic alkali. The nearly colorless solid that precipitated was crystallized from methanol, from which i t separated in colorless, silky needles that melted a t 99-100". The yield of purified material was 69%. Anal Calc'd for C*HoBrsNOa: Br, 47.19. Found: Br, 47.02. Hydrochloride of d-amino-b16-dimethyl-4,6-dibromophenol.-Forty grama of the required nitro compound was dissolved in 250 cc. of alcohol and was reduced with a mixture of stannous chloride and hydrochloric acid as explained above. The solid t h a t separated was collected, and washed with acid. A yield of 89% was obtained. The compound decomposed a t about 241". [Anal Calc'd for CsHloBr2ClNO: Hal., 58.97. Found: Hal., 58.99. I-Amino-b,6-dimethyl-4,6-dibromophenol.-Aportion of the salt indicated above was made into a thin paste with water, a slight excess of ammonium carbonate was added, and the mixture filtered. Crystallization of the residue from methanol gave small ivory needles that melted a t 141-142". Anal. Calc'd for CsHoBr2NO: Br, 54.23. Found: Br, 54.34. This aminophenol was acylated by means of standard methods, but only one acetyl-benzoyl derivative was obtained. Analytical data and other properties of these compounds are given in Table 111. I ,4,6-Trichloro-~,6-dimethylphenol.-This compound was first obtained by Katscher and Lehrm by the action of a mixture of chlorosulfonic acid, concentrated hydrochloric acid and hydrogen peroxide on 3,5-dimethylphenol. It was here prepared by direct action of chlorine on the phenol. One hundred twenty-two grams of 3,5-dimethylphenol was dissolved in 1500 cc. of carbon tetrachloride in a two-liter flask bearing a two-hole rubber stopper. Through one hole a delivery tube for chlorine extended to the bottom of the flask. The other was connected by a wide tube to the lower end of a condenser set a t an angle of about 45". The upper end of the condenser was connected to a series of three wash bottles containing caustic alkali solution. The solution of phenol was first heated, chlorine was bubbled through briskly, and the heat of reaction kept the mixture hot until the experiment was over. Considerable carbon tetrachloride distilled over into the alkali solution, and the reaction was regarded as complete when the space above the liquid in the reaction flask became greenish and the carbon tetrachloride t h a t distilled over was yellowish-green. By standing overnight the mixture deposited colorless silky needles that melted at 177-178" which was not changed by recrystallization. Con-
'' RAIFORD, J. ORG.CHEM.,2, 214 (1937).
*'KATSCHERAND
LEHEL,dfonatsh., 04, 239 (1934).
566
L. CHAS. RAIFORD AND DONALD W. KAISER
ACTION OF NITROUS ACID ON HALOQENAT%b i%6DUCTS
567
centration of the mother liquor increased the yield to 87%. The previous authors reported no yield. %,6-Dichloro-m-xyloqu~none was obtained in 64% yield of large golden plates that melted a t 177-178" by oxidation of the trichlorophenol with fuming nitric acid as directed by Kohn and Rabinowitsch in similar casesal, The physical properties of the compound agreed with those recorded by Claus and Runschke'z who first prepared it, but in a different way. 9,6-Dichloro-m-xyloquinhydrone.-Ten grams of the above finely powdered, quinone was suspended in 180 cc. of alcohol and to this there was added 3.4 g. of hydroxylamine hydrochloride 3 g. of potassium hydroxide in 10 cc. of water, and the mixture heated on a steam bath for two hours. The mixture became dark-colored, evolved much gas, and was cooled and poured into dilute sulfuric acid. The darkpurple solid that separated was purified by crystallization from alcohol and was obtained in nearly black metallic-looking plates resembling iodine, which melted a t 177-178". A test for nitrogen was negative. A mixture of this product and the quinone used as starting material melted with pronounced depression. The yield of purified material was 67%. Anal. Calc'd for Cl&14Clr04: C1, 34.46. Found: C1, 34.22. 8,6-Dichloro-m-xylohydroquinone.-Claus and Runschkea obtained a product which they state had this composition, but they gave no details concerning its preparation and furnished no analytical data for it. I t was obtained in this work by treatment of the quinone with two molecular proportions of hydroxylamine. A much more satisfactory method was reduction with stannous chloride, by which it was obtained in 86% yield. Crystallization from alcohol gave yellow needles that melted a t 225-226'. Anal. Calc'd for CaHsClzO2: C1, 34.29. Found: C1,34.25. Molecular compound obtained by the action o j nitrous acid on trichloro-sym-mxylenol (phenoquinone).-One hundred grams of 2,4,6-trichloro-3,5-dimethyIphenol was dissolved in 1800 cc. of glacial acetic acid a t room temperature, and 50 g. of solid sodium nitrite was added, in small portions, during an hour, and the mixture allowed to stand overnight. Sodium acetate that had separated was removed by filtration, and the ruby-colored filtrate was poured with stirring into six volumes of water, and the whole allowed to stand twelve hours. The orange-colored solid was collected and dried in a desiccator for three days. Crystallization from carbon tetrachloride gave crimson cubes that represented one mole of quinone and two moles of phenol. The yield was 48%. It was also obtained by mixing solutions of the quinone and the phenol in the proper proportions. When a crystal was crushed to obtain material for melting-point determination an orange powder was obtained. At 118-119" the powder became yellow but did not melt. Between 133" and 164" i t melted solwly to a yellow liquid. On cooling it became orange again. Anal. Calc'd for &H&laO4: C1, 43.29. Found: C1, 43.41,
SUMMARY
The action of nitrous acid on certain halogen substitution products of the 2,5-, 3,4- and 3,5-dimethylphenols have been studied, and the following observations have been made. *I 22
KOHNAND RABINOWITSCH, Monatsh., 48, 360 (1927). CLAWS AND RUNSCHKID, J . prakt. Chem., [2],42,124 (1890).
568
L. CHAS. RAfFORD AND DONALD W. RAISER
1. Nitrous acid reacts with 2,5-dimethy1-3,4,6-tribromophenolto replace bromine from position 4 (OH=l) by the nitro radical. Treatment of the resulting nitro compound with fuming nitric acid gives 3,6-dibromop-xyloquinone. 2. When the tribromo derivative of 3,4dimethylphenol was tested the halogen from position 6 was substituted by the nitro group. 3. Nitrous acid acts on 2,4,6-trichlor0-3,5-dimethylphenolto convert a portion of it into 2,6-dichloro-m-xyloquinonewhich combines a t once with two molecular proportions of the unchanged phenol. When fuming nitric acid is used pure dichloroquinone is obtained. Treatment of the latter with one molecular proportion of hydroxylamine gives the related quinhydrone. 4. Further evidence has been obtained to support the views previously recorded, viz., that, in general, only one acetyl-benzoyl derivative can be prepared from an o-aminophenol regardless of the order of introduction of the acyl radicals.
