March, 1947
HIGH-BOILING HYDROLYTIC DERIVATIVES OF LIGNIN
allo-ocimene, anthracene, furan, sylvane, 2,5dimethylfuran, furfuryl acetate and ergosterol. Mesacononitrile has been similarly condensed
[CONTRIBUTION FROM T H E
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with cyclopentadiene. The resultant compounds have been characterized. DAYTON, OHIO
GRADUATE SCHOOL,
RECEIVED OCTOBER25, 1946
UNIVERSITY O F WASHINGTON]
High-Boiling Hydrolytic Derivatives of Lignin BY A. BAILEY A previous publication' described the hydrolysis of butanol lignin in SOYo aqueous butanol, about 0.25 N with hydrochloric acid, a t 160' for three
Discussion.-The total yield of products is of the same order as was obtained by Hibbert and co-workers in the hydrolysis of maple lignin in hours. Products boiling below butanol, arbitrar- the presence of ethanol and hydrogen chloride, ily designated as volatile products, were isolated although the structures of the compounds obin the following yields tained show less relationship. While benzene rings and short aliphatic chains have been found Yield, Yield, 570 % in both studies, Hibbert found them combined in Methanol 2.5 Allyl alcohol 2.5 compounds having the carbon skeleton of propyl Formic acid 11.4 %-Butyraldehyde 1.6 benzene. This carbon skeleton has not been Acetone 1.9 0-Ethyl-a-methylfound in the present study although propyl comPropylalcohol 4.8 acrolein 2.8 pounds and benzene derivatives have been found. Hibbert used maple lignin while western hemlock Total 27.5 lignin was use< in these experiments. The present study was undertaken to ascertain The appearance of methoxyl in a resorcinol dethe nature and yields of additional less volatile rivative was unexpected and suggests the presence substances found in the acidic hydrolysis of lignin of a structure of the meta configuration in the from western hemlock. native lignin rather than the more common 1,2Procedure.-The source and preparation of the lignin, substituted compounds such as guaiacol, the 1,3,4the hydrolysis, and the fractionation were described in a substituted compounds such as vanillin, and the previous publication .l The present study has required, l,.l-substituted hydrogenation derivatives. The in addition, the use of appropriate high-vacuum pumps and stills. The least volatile products were collected original methoxy appears t o be satisfactorily in a molecular still of the U'ashburn type a t a pressure of accounted for in the yield of methanol, formic acid mm. of mercury, measured by a McLeod gage. and resorcinol monomethyl ether. The occurResults.-The following additional "high- rence of m-cresol in substantial quantities likeboiling" substaiices were obtained wise suggests that the 1,3-substituted benzene nucleus should be considered in relation to conYield, Yield, % % stitution. Resorcinol monon-Butyric acid 1.0 It is possible that the n-butyric acid should be methyl ether 7.3 Guaiacol 0 3 regarded as derived from the butanol solvent m-Cresol 6.7 Vanillin 0.2 rather than from the lignin. Constitiltional conclusions that might tentaTotal 15.5 tively be drawn from the above experiments are In addition to these compounds, 0.67, of com- these : hydrolysis (and perhaps mild oxidation as plex phenols was obtained but the quantity was well) converts 40y0 of the lignin into identifiable not adequate for characterization. A resinous, compounds. About one-third are phenolic, and alkali-soluble fraction was also obtained. the remaining two-thirds are short-chain, aliIdentification.--; 1) Resorcinol Monomethyl Ether.phatic compounds. There is general similarity The S-a-naphthylcarbaniate melted a t 127-128" and the between these products and previously isolated aryloxyacetic acid a t 115-116". (20) m-Cresol.--The 3,5-dinitrobenzoate melted a t deriiratives of lignin. In view of the many prod164 , mixed melting point of unknown and authentic ucts of reaction, and the 60% fraction of the lignin sample of m-cresol showed no depression, arid N-e- not converted to identifiable products, it does not naphthylcarbamate melted a t 125-126". (3) +Butyric Acid.-The S-benzylthiuronium salt appear justified to propose a constitutional model from the data of these experiments. ineltzd a t 144' and the p-phenylphenacyl ester a t 8080.3 . While the original intent was t o learn the ef (4) Guaiacol.--The p-nitrobenzoate melted at 90fects of acidic hydrolysis, the nature of the com90.5' and the 3,5-dinitrobenzoate, crystallized from alcopounds identified suggests that mild oxidation hol, a t 1.10-140.4" ( 5 ) Vanillin.--The oxime melted a t 115-115.7' and also occurred. the 2,4-dinitrophmylhydrazone (from acetic acid) a t The discussion in the previous paper,' relating 269 '. to the more volatile products identified, does not appear to be in need of correction ir the light of (1) A. Bailey, THISJOURNAL, 64, 22 (1942).
GILBERTSTORK
576
this later investigation and should be consulted for further comments.
Summary Five compounds were identified as high-boiling hydrolytic derivatives of lignin, in a yield of 15.570. Together with the six low-boiling compounds in 27.5% yield, reported in an earlier pub-
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Vol. 69
lication, the total yield of the reaction came to 43.3%;;. The compounds identified were generally similar to known derivatives of lignin preparations. The experimental data were not considthe proposa1 Of a 'Onered adequate to stitutional model. SEATTLE, WASHINGTON
RECEIVED NOVEMBER 18, 1946
RESEARCH DEPARTMENT OF THE LAKESIDE LABORATORIES, INC. ]
The Base Effect in Catalytic Hydrogenation. A Simple Synthesis of 6-Methoxya-tetralone BY GILBERTSTORK' I n an attempted preparation of 0-tetralone by ferentially in the unsubstituted ring throws some the catalytic hydrogenation of /3-naphthoSa with doubt on Palfray's conclusion2' that a hydroxyl Raney nickel a tetralol fraction was obtained group facilitates the reduction of a n aromatic which solidified and was found to consist mostly ring. It is suggested that in a polycyclic aromatic of the fihenolic ar-tetrahydro-0-naphthol. This compound that ring will become reduced, the result could not be reconciled with that of pre- reduction of which will result in the smallest loss vious investigators who had studied the catalytic of resonance energy by the system. If this be hydrogenation of 0-naphthol to 4 s tetrahydro so, then one would expect that in a system derivative, using nickel or Raney nickel catalysts, like naphthalene almost any substituent introand who had reported the product of the reaction duced in one ring will stabilize that ring toward to be the non-phenolic ac-tetrahydro-0-naphthol.2 hydrogenation, and the normal product of the Only one of these workers2c had reported the Raney nickel hydrogenation of 0-naphthol would simultaneous formation of approximately equal then be expected td be ar-tetrahydro-P-naphthol, as was indeed found. amounts of both isomers. It should be pointed out, however, that this This lack of agreement prompted us to reinvestigate the catalytic hydrogenation of /3- conclusion will be valid only in the absence of naphthol with Raney nickel. It was found that, other factors which under the proper conditions contrary t o the results previously reported with may well play a determining part in directing this catalyst,2d*e*f the absorption of two moles of the hydrogenation. For instance, it would not hydrogen per mole of 0-naphthol brings about the be expected that the presence of acid in the reducpreferential saturation of the non-phenolic ring tion medium would materially affect the course with the formation of the phenolic ar-tetrahydro- of the reduction of 0-naphthol since this would 0-naphthol. Some of the isomeric ac-tetrahydro- cause little change in the molecule undergoing P-naphthol is also formed, a typical yield being reduction. I n the presence of some diethylamine 66% of 5,6,7,8-tetrahydro-P-naphthol .and 33% hydrochloride or acetic acid in the alcohol soluof the non-phenolic i ~ o m e r . ~ The two compounds tion the hydrogenation was somewhat slower can easily be separated by extraction of the ar- than in a neutral medium, but the products from tetrahydr0-/3-naphthol with very dilute (2%) these reductions were qualitatively similar to sodium hydroxide solution. More concentrated those obtained without acid, and the main consolutions fail to dissolve the sodium salt. Once stituent was again the phenolic 5,6,7,8-tetrahyseparated, the two isomers can be readily differ- dro-0-naphthol. I n the presence of added base, however, the entiated by comparing their behavior toward situation is quite different. In the iirst place, diazotized aromatic amines. The finding that @-naphthol is reduced pre- the phenolic moiety will be more strongly adsorbed on the basic catalyst than the rest of the (1) Present address: Converse Memorial Laboratory, Harvard molecule, and secondly i t will have the possibility University, Cambridge, Massachusetts. (la) Stork and Foreman, THISJOURNAL, 68, 2172 (1946). of tautomerizing t o the non-aromatic a,p-un(2) (a) Schroeter, Svanoe, Einbeck, Geller and Riebensahm, Ann., saturated ketone system 486, 83 (1921); (b) Brochet and Cornubert, Bull. SOC.chim., Si, 1280 (1922); ( e ) Kimura, J. Chcm. SOC. J a p a n , 51, 208 (1930); C. A., 28, 720 (1932); (d) Musser and Adkins, THISJOURNAL, 80, 664 (1938); (e) Palfray, Compt. rend,, 206, 1976 (1938); (f) Palfray, Bull. SOC. chim., [ 5 ] 7 , 407 (1940). (3) Professor Homer Adkins has told us that H. P.Schultz, working in his laboratory, bad observed the formation of the phenolic 6,6,7,8-tetrahydro-B-naphthol in a Raney nickel hydrogenation of
p- naphthol.
As a matter of fact, when the catalytic hydrogenation of P-naphthol was conducted in the
