SCHRYVER : RESEARCHES ON CAMPHORIC ACID. 559

LVI I I.-Researches O I L Cumphoric Acid. By SAMUEL BARNETT SCHRYVER.

(‘ TN experimenting on the constitution of camphoric acid, one of t h e most characteristic properties which at once presents itself is the great stability of the acid, which makes it very difficult to attack it by re- agents and thus resolve i t into smaller molecules.”

With these words, Prof. W. H. Perkin and Dr. Crossley preface their paper, which opens the current volume of the transactions of this Society. They may equally well stand at the head of the present com- munication. It seems desirable, however, not only that camphoric acid should be resolved into smaller molecules, but also that the re- actions by which this purpose is accomplished should take place a t comparatively low temperatures. Wi th this purpose in view, the following work was undertaken.

Sodium ethoxide acts in various ways on the ethylic salts of mono- basic lactono acids, t o which class camphanic acid (oxycamphoric acid) belongs; terebic acid, for example, is converted by this means into the unsaturated teraconic acid (Roser, Annalen, 1883, 220, 255). It was found that no action took place when ethylic camphanate was treated either by sodium ethoxide in alcoholic solution, or by sodium in ethereal solution, under varying conditions.

Lauronolic Acid.

Having failed to prepare from camphoric acid an unsaturated acid in the way described above, attention was next turned to lauronolic acid, which was originally prepared by Woringer (Anmden, 1885,227, 7) by the destructive distillation of camphanic acid. More recently, however, Aschan (Ber., 1894, 27, 3507) showed that it could be pre- pared directly from bromocamphoric anhydride by treating it with sodium carbonate, thereby proving that the bromine atom is in the a-position. Previously, however, to the publication of Aschan’s paper, the author of the present communication had commenced the investi- gation of lauronolic acid, more especially of the oxidation products of this substance, and on informing Dr. Aschan of this, he courteously abandoned this field ; the author takes this opportunity of expressing

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560 SCHRYVER : RESEARCHES ON CAMPHORIC ACID.

his obligations to Dr. Aschan, and of acknowledging the very great assistance he has received in carrying out the following difficult and tedious work by the publication above referred to.

Preparation of Bronzocampho~*ic Anhydride and Luuronolic Acid.

The method adopted for preparing these substances mas essentially that of Aschan, namely, converting camphoric acid first into its chloride by means of phosphorus pentachloride, and brominating the product thus formed in presence of the phosphorus compounds. Usually, 350 grams of acid were brominated at a time, 50 grams of acid and 105 grams of pentachloride being introduced alternately into the flask, as it is not advisable to mix the whole of the 250 grams and the corresponding amount of chloride at once. After brominating, the contents were thrown into a large quantity of water, the mixture being cooled as soon as the reaction begins to get violent; the lauronolic acid was then prepared from the product obtained, exactly according to Aschan's directions. Altogether about 160 grams of lauronolic acid are obtainable from 1 kilogram of camphoric acid.

Oxidcction of Lauronolic Acid by Potassiunz Pevmanganate.

Ten grams of lauronolic acid mere dissolved in dilute sodium carbon- ate solution, and ice cold 3 per cent. solution of potassium permangan- ate added drop by drop, shaking constantly; after the quantity corre- sponding with 4 atoms of available oxygen per molecule of acid has been added, oxidation with unsaturated acids generally proceeds very slowly, but this is not the case with lauronolic acid, as much more permanganate solution was added without any apparent retardation of the oxidation. The products of oxidation, which were isolated in the usual way, consisted of some unchanged lauronolic acid, small quanti- ties of volatile fatty acids, oxalic acid, and another acid giving an insoluble lead salt, obtained after the oxalic acid had been separated as calcium oxalnte, but in quantity far too small for further investigation. No other definite product was obtained. I n this respect, lauronolic acid behuves like t h tetyahydrophthalic acids investiyuted 6y von Bayer, and darers from the mc(l'oyity of ordinary unsuturuted acids.

For this reason, snd owing to the ease with which a nitro-derivative was formed (see below), it was thought tha t camphoric and lauronolic acids were hydrogenised benzene derivatives, and an attempt to synthe- sise camphoronic acid on this assumption mas made (Trans., 1898, 73, 68).

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SCHRYVER : RESEARCHES ON CAMPHORIC ACID. 561

Action of Nitric Acid on Lauronolic Acid.

On treating lauronolic acid with nitric acid, a violent oxidation took place ; the solid neutral product which separated was collected, and the filtrate neutralised with caustic soda and evaporated down t o a small bulk ; on adding silver nitrate, a copious, white precipitate was formed, which, after being mashed with water, alcohol, and ether, mas sus- pended in ether and decomposed by hydrogen sulphide; after filtering from the silver sulphide, and evaporating the ether, a solid acid was left which proved to be oxalic acid.

Ivitrocam~r'LoZuclone.*

The solid substance mentioned in the preceding paragraph as obtaiiled on treating lauronolic acid with nitric acid proved on investigation t o be nitrocampholxctone, C9H,,0,*N0,. To obtain the best yield of this compound, the fctllowing method was employed ; lauronolic acid in quantities of 5 grams a t a time is dissolved in four or five times its volume of concentrated nitric acid of sp. gr. 1.45, and very gently warmed over a small flame in a reflux apparatus; as soon as action commences, the flask containing the mixture is immersed in cold \;rater. When the violent reaction which takes place, accompanied by large quantities of nitrous fumes, abates, the mixture is cooled and poured into several times its volume of cold water. The oil which separates very quickly solidifies to a yellow, flocculent mass ; this is collected, washed with cold water, and, after being dried on a porous plate, is re- crystallised from absolute alcohol, from which it separates in nearly white, skeleton, quadratic prisms melting a t 170". This product is generally pure enough for all further operations. Another crop of crystals can generally be obtained by adding a little water to the mother liquor, bnt if too much water is added an oil separates. The crystals are almost insoluble in water and dilute alkalis, neutral to litmus paper, and readily soluble in alcohol, ether, light petroleum, and most other organic solvents. For analysis, they were twice crystallised from absolute alcohol, and finally from light petroleum, separating from the latter in the form of scalenohedric quadruplets melting at 171'. They volatilise even below 100'.t

* Canipholactone is isomeric with lauronolic acid and obtained from i t very readily

.t A small quantity of this snbstance (a fraction of a gram) mas obtained by Keyher One of the analyses

by treatment with acids.

(Disscrt., Leipzig, 1891), but he did not recognise its nature. quoted is taken from his paper.

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562 SCHRYVER : RESEARCHES ON CAMPHORIC ACID.

0.2062 gave 0.4140 CO, and 0,1234 H,O. 0.2045 ,, 0.4111 CO, ,, 0.1232 H,O. 0.3618 0.1946 ,, 13.0 C.C. ,, ,, 19' and 739 mm. Found.

,,

C=54.75 and 54-79 ; H=6*65 and 6.69; N=7*05 and C,H,,O,*NO, requires C = 54.29 ; H = 6.53 ; N = 7.04 per cent.

Careful experiments were made to obtain an oxime derivative but with a negative result, so that the compound is not a ketone.

Attempts were made t o produce this nitro-derivative without warm- ing ; lauronolic acid is, however, not acted on in the cold even by fuming nitric acid, when in acetic acid solution, and consequently, owing to oxidation, the yield of nitrocampholactone is not large. Generally, the amount of crude nitro-compound only amounts to about one-third of the weight of the lauronolic acid used. Nitrocampholac- tone can, however, be best prepared by the action of nitrogen peroxide on lauronolic acid.

21.8 C.C. inoist nitrogen a t 9' and 757 mm.

7.44.

Action of Nitrogen Peroxide on Lauronolic Acid.

BQhal and Blaise (Compt. md., 1895, 121, 238) have shown that campholenic acid absorbs nitrogen peroxide, forming a somewhat unstable blue compound which they called '' cerulaeonitrosodihydro- campholenoactone," and this, by the further action of nitrogen peroxide, yields the colourless nitro-derivative. Tiemann subse- quently (Ber., 1897, 30, 412) prepared the same compound by the action of nitric acid on campholenic acid. All three observers are agreed as to the nature of this substance, and of the error of Kachler and Spitzer, who obtained it previously and called it nitrocampholenic acid.

Lauronolic acid appears to behave in every way like campholenic acid ; in fact, nitrocampholactone can be more :conveniently prepared by the action of nitrogen peroxide on lauronolic acid than by the action of nitric acid. A few grams of lauronolic acid in a shallow layer in a flat-bottomed evaporating basin are exposed to the fumes of nitric peroxide, obtained by heating lead nitrate, and passed over the acid by means of an inverted funnel ; the fumes are rapidly absorbed and the liquid becomes dark greenish-blue. After a time, oxidation takes place, the liquid becomes warm and rapidly loses its colour, and on cooling solidifies to an indistinct, crystalline mass, which, however, still has a greenish tint. The solid, after being exposed to the air for some time, and finally dried in a vacuum over quicklime to get rid of the excess of acid, is spread on a porous plate and the dried mass recrystallised

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SCHRYVER : RESEARCHES OX CAMPHORIC! ACID. 563

from absolute alcohol. with the product obtained by the action of nitric acid.

isolated ; a better method is described in detail below.

The nitrolacto ne thus prepared is identical

The nitroso-derivative prepared in the above way was not directly

Action of N i t k Acid on Camphotactone.

When campholactone is treated with concentrated nitric acid, no action takes place in the cold, but on warming, a violent oxidation takes place, and on cooling, a certain quantity of nitrocampholactone separates. The yield obtained, however, is considerably smaller than that obtained by the action of nitric acid on lauronolic acid.

Reduction of the Nitrolactone by Zinc Dust and Glaciccl Acetic Acid. Hydroxylaminolact one.

Nitrocamphdactone, dissolved in about ten times its weight of glacial acetic acid, is cooled by ice cold water, and zinc dust added in small quantities at a time ; as soon as the further addition of zinc dust causes no very appreciable rise in temperature, the action is complete. The solution is filtered from the excess of zinc dust and zinc acetate, the residue washed with as small a quantity of water as possible, and the filtrate and washings made strongly alkaline by concentrated solution of caustic soda, the temperature being kept low meanwhile by cooling with ice; the turbid liquid is then extracted about six times with ether. On distilling off the ether, a syrup is left, which very rapidly solidifies to a crystalline mass of bluish-green tinge; as the product is readily soluble in hot water, it can easily be separated from the small quantity of nitrosolactone which is formed at the same time, and is described in greater detail below. From the hot aqueous solution thus obtained,the substance separates incharacteristic, twinned. quadratic prisms ; these are but slightly soluble in light petroleum, but readily in ether, and can be conveniently recrystnllised by dissolving in the latter and precipitating by the addition of light petroleum. When finally recrystallised from absolute ether, they melt sharply at 148".

0.2075 gave 0,4468 GO, and 0.1570 H,O. 0.1976 13.1 C.C. moist nitrogen at 1 5 O and 730 mm. N = 7-51.

C,H,,O,*NH*OH requires C = 58-47 ; H = 8.40 ; N = 7.45 per cent.

This compound, from the results of the analysis, appears to be the hydi*oxylamino-derivative. It is not of very basic character, and does not give a precipitate when gaseous hydrogen chloride is passed into its ethereal solution. Furthermore, it reduces ammoniacal silver nitrate

C = 58.38 ; H = 8-11. ,,

0.2038 ,, 14.2 c.c ,, 9 , 19' ,, 740 mm. N=7*82 .

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564 SCHRYVER : RESEARCHES ON CAMPHORIC ACID.

cclmost immediately in the cold and also Fehling's solution, and is oxidised by ferric chloride.

Bamberger (Bey. 1894, 27, 1347 and 1548) shows that nitrobenzene is capable of being reduced by means of zinc dust in water, and Wohl (ibid., 1432) obtained a similar result ; Bamberger finds, however, that phenyl- hydroxylamine is very unstable in presence of acids and also when boiled with water. Gattermann (Ber., 1893, 26, 1544 and 2810, also 1894, 23, 1987) shows that various aromatic nitro-derivatives, on reduction by electrolytic hydrogen, yield amidohydroxy-derivatives, the hydroxylamine derivatives apparently being produced in the first. instance, and changing in the presence of acids into the isomeric amidohydroxy-compounds. The product obtained by the reduction of nitrocampholactone by the method described above was, however, obtained in acid solution, and is so stable in the presence of water tha t it can be recrystallised from it.

It appears, therefore, that, whereas, on the one ?Land, lauronolic mid, like an aromatic devivative, on treatment with nitric acid yields a nitro- derivative with the greatest ease, this nitro-derivative, on reduction, yields cc hydroxykamino-compound which is far move stable tlmn (6 similar compound obtainccble f r o m cc benzene derivative.

This production of a hydroxylamine is noteworthy.

Action of Ferric ChloTide on ~ y d r o x ~ ~ c ~ n ~ ~ ~ ~ o c n m p ~ ~ o ~ a c f o ? z e Nitrosocampho Zactone.

It has been mentioned above that hyd roxylarninocampholactone reduces ferric chloride; by this means, a nitroso-derivative can be produced. On adding ferric chloride in excess to a solution of the hydi-oxylamino-compound in water, a light, bluish-green, flocculent precipitate is formed wh'ch is excessively soluble in ether, the precipitate being immediately dissolved on shaking with ether, yielding a dark bluish-green solution; on evaporating the ether, the nitroso- derivative remains behind as a bluish-green, indistinct, crystalline mass of pungent, camphor-like odour. It is excessively soluble in ether, light petroleum, ethylic and methylic alcohols, and most organic solvents, and for this reason i t is extremely dificult to purify it. It can be prepared directly from the nitro-derivative without the isolation of the intermediate hydroxylamino-derivative ; for this purpose, the nitro-derivative is reduced by means of glacial acetic acid and zinc dust in the manner above described and the zinc acetate and zinc dust filtered off; water is then added, and any unchanged nitro- derivative which may be precipitated is filtered off. To the filtrate, ferric chloride is directly added, the precipitated nitroso-compound extracted with ether, and the ether evaporated, when the nitroso-deriva-

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SCHRYVER : RESEARCHES ON CAMPHORIC ACID. 565

tive remains behind in acetic acid solution ; on adding water, the nitroso- derivative separates as an oil which, on standing in a desiccator, solidifies almost entirely. The bright green, crystalline plates thus obtained, whendried on a porous plate to separate them from a small amount of impurity, melt fairly sharply at 117". The specimen used for analysis was recrystallised from methy lic alcohol.

0,2096 gave 13.5 C.C. moist nitrogen a t 9' and 748.3 mm. N = 7-71. C,H,,O,*NO requires N = 7.65 per cent.

The substance analysed, although crystalline, was somewhat resinous to the touch, and probably the melting point given is not absolutely correct, owing to the difficulty of purifying comparatively small quantities, ,The nitroso-derivative, with phenol and con- centrated sulphuric acid, gave a dark green solution, becoming pink on diluting with water and giving a transient green coloration on the ad- dition of caustic potash (Liebermann's reaction for nitroso-compounds). There is no doubt, therefore, as to the chemical nature of the compound.

Reduction of NitrocnmphoEactone by Fin and Hydrochloi-ic Acid. Aminocumpholact one.

The amino-derivative is obtained by reducing the nitro-derivative with t in and hydrochloric acid; for this purpose, it is suspended in strong hydrochloric acid and granulated t in added, when the solution becomes warm, and the solid nitro-derivative gradually disappears, giving rise to a dark green solution ; on further action of the nascent hydrogen, the solution loses its colonr, finally becoming light yellow. The nitroso-compound appears to be formed as an intermediate pro- duct; the course of the reaction, therefore, can be readily followed. When the reduction is complete, a concentrated solution of caustic soda is added to the cooled acid liquid until the mixture is strongly alkaline, and the turbid liquid is then extracted six or seven times with e ther ; on evaporating the ether, the aminolactone is left. If the pure nitro-compound had been used and the operation carefully carried out, the amino-derivative solidifies in a very short time to a mass of hard crystals, which, after a couple of recrystallisations from water, are quite pure. As a general rule, however, the amino-deriva- tive is obtained as an oil which only partially solidifies, even after standing for some days in a vacuum ; in this case, it is best purified by dissolving the dried substance in absolute ether, and precipitating a s hydrochloride by dry hydrogen chloride. The salt then separates as a snow-white, crystalline mass which is very soluble in water ; the yield of hydroclrloride from tlie nitro-compound is a little more than 75 per cent. of the theoretical. To obtain the free base, the hydro- chloride is dissolved in a small quantity of water, and the solution put into a separating funnel under ether; potassium carbonate is then

VOL. LXXIII. P P

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566 SCHRYVER : RESEARCHES ON CAMPHOKIC' ACID.

added drop by drop in strong solution, and the free base immediately extracted with ether after each addition of alkali. On evaporating the ether under diminished pressure, the base is left as a snow-white, crystalline mass readily soluble in ether and water, but only slightly in light petroleum. For analysis, it was twice recrystallised from hot water, from which it separates in large, pearly plates melting at 39" ; these plates, however, contain a considerable quantity of water, but on drying in a vacuum they effloresce and give up water, the dried crystals melting at 66".

0,2014 gave 14.9 C.C. moist nitrogen a t 21' and 740 mm. 0.1370 ,, 0.3230 CO, and 001130 H,O. C = 64.28 ; H = 9.16.

N = 8.35.

C,H1,O,*NH, requires C = 63.90 ; H = 8.88 ; N = 8.28 per cent.

The hydrochloride precipitated from its ethereal solution as above described is dissolved in water, and, if necessary, decolorised by boiling with animal charcoal ; on filtering and evaporating, the hydrochloride separates in white, silky needles, which are dried on blotting-paper and then in vacuum, and finally purified by dissolving in absolute alcohol and slowly precipitating from the alcoholic solution by ether. They are thus obtained in small, white prisms which decompose without melting above 200O.

0.2312 gram requires 11-6 C.C. AgNO, solution, of which 1 c.c.= 0.00348 gram Ag. C1= 17.46.

C,H,,O,*NH,,HCI requires C1= 17.76 per cent.

PZatinochZoride.-On adding platinum tetrachloride in strong solu- tion to a concentrated solution of the hydrochloride, the platino- chloride separates in glistening, golden-yellow needles, but only after standifig f o r some time, as it is very soluble in water. The crystals, after being drained, are dried on a porous plate, and finally purified by dissolving in absolute alcohol and precipitating from the alcoholic solution by ether. The salt is thus obtained in pale, golden- yellow spangles which decompose without melting above 200". A n analysis shows that they are the platinochloride, not of the amino- lactone itself, but of the corresponding aminohydroxy-acid.

0.3421 gave 0.0850 Pt. Pt = 24-84. 0.6432 ,, 0.1587 Pt. Pt = 24.67.

( C,H,50,*NH2)2,H,PtC16 requiror; Pt = 24.90 per cent. (C,H,,02*NH,),,H2PtC1, ,, Pt = 26.1 ,,

Action of Potassium Nitrite on the Hydrochloride of the Anzine.

On treating a strong, ice cold solution of the hydrochloride of the amine with potassium nitrite, the nitrite of the base separates. This, however, is very unstable, and decomposes on warming gently with

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SCHRYVER : RESEARCHES ON CAMPHORIC ACID. 56'7

water giving two products; an oil separates, but on adding caustic soda a part of this dissolves, and on extracting the alkaline solu- tion with ether a neutral oil is obtained with characteristic, sweet, pepperminf-like odour. On acidifying the residual alkaline . solution, and extracting again with ether, a substance is obtained which solidifies in part on standing ; the solid crystals thus obtained, after being dried on a porous place, are readily soluble in ether, but not in light petroleum, and can, therefore, be purified by dissolving in the former solvent and precipitating the solution by the latter. They then melt at 118".

The best conditions for carrying out this reaction have not yet been obtained.

These compounds must be reserved for future investigation. Tiemann (Bey. , 1897, 30, 41 4) has shown that aminodihydrocampholenolactone, by a similar reaction, yields hydroxydihydrocampholenolactone and a campholenolactone, whilst Angeli (Bey . , 1893, 26, 1718) obtained camphenone from aminocampholenolactone. Probably an analogous reaction here takes place, the elements of water being removed at the same time that the amino-group is replaced by the hydroxy-group.

Conclusions.

The reactions described above may be schematically represented as follows.

Lauronolic acid

Nitrosocampholactone further action of NO, Nitrocampholactone m. p. 117" m. p. 171"

(D

t

9 x J 1"

Hy droxy Iamino- camp holac t one m. p. 148O

Aminocampholactone m. p. 66"

18 1..

H ydroxy campholac t one m. p. 118"

and another substance.

Piloty has recently (Bey . , 1898, 31, 219) been investigating aliphatic nitroso-derivatives, and he concludes from a large number of examples that true nitroso-derivatives are only obtained with ease from those

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568 SCHRYVER : RESEARCHES ON CAMPHORIC ACID.

hydroxylamino-compounds in which the -NH*OH group is attached to a tertiary carbon atom. This conclusion has such an important bearing on the above work that it seems worth while to give Piloty's own words. Speaking of the nitroso-derivatives, he writes.

'' Alle diese Substanzen haben das gemeinsame Merkmal das sie die Btickoxylgruppe an Kohlenstoff gebunden erhalten der keinen Wasser- stoff mehr besitzen. Wohl (Ber., 1894, 2'7, 1435), und Bamberger (ibid., 1537) fanden gleichzeitig das Phenylhydroxylamin durch dxydationsmittel in Nitrosobenzol verwandelt werden kann. . . . . Aus der Gesamrdtheit dieser Thatsachen muss der Schluss gezogen werden dass eine ausgesprochene Neigung xur Bildung wahsver Nit?*ooso- verbindungen nur den K6rpem eigen ist welche den Stickstof an ein in Uebrigen tertitis. gebundenes Kohlenatofatom gekuppelt erhalten."

Now the formulae for camphoric acid most in accordance with the known constitution of camphoronic acid are those of Bredt and W. H. Perkin, junr., namely,

CH3 CH, CH*COOH. ''OH ~ " 3 > y + p x - c o o H CH,CH, and

These can give rise to the following lauronolic acids,

CH, CH, CH3 CH3 \ /' \c/ C

and the following nitrosolactones,

CH, CH, CH, CH, CH, CH,

rC-\ I I I co*o. l

\/ \/ \/ /-'-\ and rC-\

CH,*C.C CH*NO I 0'0.1

CH,* C. CH2 CH3*C*CO*O*C

CH,-CH*NO NO*CH-CH CH2-CH

The nitroso-group must in each case be attachzd to the carbon next to the lactone hydroxyl group, owing to the formation of the nitroso- lactone by direct addition of KO2 to the unsaturated lauronolic acid.

In none of the above cases is the nitroso-group attached to a tertiary carbon atom. Hence, if Piloty's generalisation is universally ap- plicable, neither the Bredt nor t.he Perkin formula can represent the true constitution of camphoric acid.

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STUDIES OF THE TERPENES AND ALLIED COMPOUNDS. 569

Apart from this question, iti,.can readily be seen from the above forniulae that, by replacing the nitro-group by the hydroxy-group, we can obtain a product capable of undergoing various reactions at com- paratively low temperatures which might throw much light on the constitution of camphoric acid, The investigation of the product thus obtained would, however, entail the use of very large quantities of camphoric acid, and could hardly be undertaken single-handed under the conditions of ordinary laboratory work.

The greater part of the above work was carried out a t University College, Liverpool, during my tenure of a demonstratorship of tha t Institution, and it was completed a t the Royal College of Science, London. The expenses were partly defrayed by two grants (in 1834 and 1895) from the Governnient funds a t the disposal of the Royal Society, and to the Committees charged with the distribntion my best thanks are due.

Addendum.

I n the Proceedings, 1898, page 111, there is a communication from Messrs. R. W. Collinson and W. H. Perkin on lauronolic acid, in which they state that, on oxidising the latter, an acid of the formula C,H,,O, is formed. Although this result is apparently not in harmony with those I have obtained, the contradiction seems to me to be more apparent than real, for i t is known tha t unsaturated acids can be oxidised in stages by treatment with permanganate solution, and the acid they obtained is doubtless a n intermediate product of oxidation.

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