CCCXXIV.-TT;Tbe Oxidution of Xucrose by Nitric Acid. by FREDERICKDANIEL CHATTAWAP and HINTONJOHN HARRIS

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THE OXIDATION OF SUCROSE BY NITRIC ACID. 2703 Published on 01 January 1922. Downloaded by North Carolina State University 09/12/2014 09:52:42. CCCXXIV.-TT;Tbe Oxidution of Xucrose by Nitric Acid. By FREDERICKDANIEL CHATTAWAP and HINTONJOHN HARRIS. FORover a hundred and fifty years the action which takes place when sucrose is oxidised by nitric acid has attracted the attention of chemists, and its spectacular character, from the torrents of nitrogen peroxide evolved, still makes it a favourite laboratory experiment. It has considerable historical interest, for it was from the product of this action that Bergman (“ Opuscula Physica et Chemica,” Vol. 1, p. 238. De acido Xacchari) about 1776 first isolated oxalic acid. From the testimony of several of his friends, it appears that Scheele had identified the acid shortly before, though whether he obtained it from sugar or from wood sorrel is not clear, for he never published any account of his work. For a View Article Online

2704 CHATTAWAY AND HARRIS : long time, Bergman's process was in everyday use for making oxalic acid, but apparently no very detailed account of it was published until Thompson (Pharm..J., 1848-1849, 8, 117) took up the subject about 1848 and described what he had found to bc thc most satisfactory procedure. Since that time, little close attention has been directed to the subject, and oxalic acid has been generally regarded as the sole end-product. A re-examination of the reaction, however, has shown that, in addition to oxalic acid, mesoxalic acid is formed in considerable quantity and that the violent oxidation of sugar by nitric acid is the most advantageous way of preparing this little-known compound. Mesoxalic acid is easily detected, being a ketonic acid and form- ing a well-characterised hydrazone with any aroqtic hydrazine. It can be isolated conveniently by making use of the sparing solu- bility in water of its sodium salt. About 11 grams of sodium mesoxalate can be obtained from the oxidation of 100 grams of sugar, about 40 grams of crystallised oxalic acid being at the same time produced. Mesoxalic acid is formed in approximately equal amount when dextrose, levulose , lactose, maltose , or starch is similarly violently oxidised by nitric acid.

EXP E R IM E N T A L. When powdered or granulated sucrose is added to about fourteen times its weight of strong nitric acid, it dissolves at the ordinary temperature. On slowly heating the solution, it assumes a pale yellow tint which gradually deepens to it light and finally to a dark brown, owing to the formation of oxides of nitrogen. When the

Published on 01 January 1922. Downloaded by North Carolina State University 09/12/2014 09:52:42. temperature reaches 72-75', vigorous action sets in and if external heating be now stopped the temperature rises rapidly to about 94-95". This violent action continues for some time and the liquid appears to boil vigorously from the rapid disengagement of nitric oxide, nitrogen peroxide, and carbon dioxide. The temperature remains at first approximately constant, but gradually falls as the action diminishes in violence and finally apparently ceases. If other proportions of sugar and nitric acid are used or the liquid is heated with varying degrees of rapidity, violent action commences at slightly different temperatures, but the highest temperature reached without further external heating does not much exceed 94-95'. If fuming nitric acid is used, violent action begins of itself after some ten minutes' standing at the ordinary temperature without any preliminary heating. Neither the exact View Article Online

THE OXIDATION OF SUCROSE BY NITRIC ACID. 2705 amount of strong acid initially used nor its exact strength much affects the phenomena observed, and the oxidation of the sugar into simple products is by no means complete when violent action subsides. Further oxidation, however, takes place on again heating and oxalic and mesoxalic acids are now the main products. On cooling the suitably concentrated liquid, the bulk of the oxalic acid crystallises out, and a large part of the excess of nitric acid still remaining can be got rid of as sodium nitrate by the addition of an appropriate amount of solid sodium carbonate. Mesoxalic acid is present in the residual acid liquid in considerable quantity and separates as its sodium salt after complete neutralisation. In order to get consistent results, a definite procedure has to be carefully followed, as even trifling variations, such, for example, as evaporating in a flask instead of an evaporating dish and thus prolonging the heating, much affect the yield of mesoxalate.* The following has been found the best method for preparing and isolating sodium mesoxalate. To 50 grams of sucrose in a 1500 C.C. flask are added 700 grams of nitric acid (d 1-41), and the mixture is heated to about 72-75'. The source of heat is removed, the violent action allowed to subside-this usually takes about twenty- five minutes-and the liquid poured into an evaporating dish and boiled rapidly until, when cooled to 74", it occupies a volume of 112 c.c.? The liquid is now transferred to a flask and cooled with constant shaking to - 5". The oxalic acid, which separates and usually amounts to about 21 grams, is filtered by the aid of the pump, using a Buchner funnel and at least three filter-papers or better an asbestos pad. The filtrate is again placed in the evaporating basin and 50 grams of anhydrous sodium car- bonafe are added in three portions; this causes the temperature Published on 01 January 1922. Downloaded by North Carolina State University 09/12/2014 09:52:42. to rise to about 70". The solution is cooled to - 5" and the sodium nitrate which separates and usually amounts to about 50 grams is filtered off. To the filtrate 12 grams of anhydrous sodium carbonate are added and then a saturated aqueous solution of * The addition of vanadium pentoxide, as recommended by Naumann, Moeser, and Lindenbaum (J. pr. Chem., 1907, [ii], 75, 146), which causes the oxidation of sugar by nitric acid to take place at a lower temperature with a consequent larger yield of oxalic acid if a limited amount of nitric acid is used, causes complete oxidation of the sugar to carbon dioxide if the quantities of nitric acid and sugar given above are employed, so that on evaporation no residue is left. t During the evaporation the temperature of the boiling liquid rises from about 107" to ill", and the hot liquid, when poured into a cylinder for measurement, usually cools to very near 74". It is essential that the volume at 74" should be exactly 112 C.C. as the amount of free acid remaining after partial neutralisation which determines the subsequent separation of the mesoxalate in good yield depends almost entirely on this. View Article Online

2706 CHATTAWAY AND HARRIS :

sodium carbonatc until the liquid reacts distinctly alkaline ; about 40 C.C. of the solution are usually required. The liquid which while acid is pale yellow in colour becomes pale brown when alkaline. The alkaline liquid is kept for twenty-four hours, when 5-6 grams of sodium mesoxalate separate as a colourless, crystalline powder. About a further gram remains dissolved in the alkaline mother- liquor and can be recovered as hydrazone. The sodium mesoxalate, C(OH),(CO,Na),, thus obtained is practically pure. Two grams of a specimen of the salt thus prepared yielded 2-26 grams of mesoxalic acid phenylhydrazone, the theoretical amount being 2.3 grams. The hydrazone thus obtained melted with decomposition in one minute when kept at a constant temperature of 166". When placed in a bath at 166" and heated moderately rapidly, it melted with decomposition at about 173". It was moderately easily soluble in boiling alcohol, acetone, or chloroform, and sparingly soluble in boiling water, from all of which it crystallised in pale yellow, slender, flattened prisms. To complete its identification with the hydrazone first prepared by Fischer and Elbers (Ber., 1884, 17, 578), it was completely analysed (Found : C = 51.8 ; H = 3.78 ; N = 13-67. Calc. for C,H,O,N,, C = 51.91 ; H = 3.87 ; N = 13.46 per cent.). It was also compared and found to be identical with the hydrazone prepared from specimens of mesoxalic acid obtained from uric acid and from malonic acid.

Oxidation of other Carbohydrates by Concentrated Nitric Acid. The other common carbohydrates, dextrose, laevulose, lactose, maltose, and starch also yield mesoxalic acid when violently Published on 01 January 1922. Downloaded by North Carolina State University 09/12/2014 09:52:42. oxidised by nitric acid. Using the quantities of carbohydrate and nitric acid given above, the phenomena observed are very similar to those noted when sucrose is employed and the yields of oxalic acid and sodium mesoxalate are approximately the same, the amount of oxalic acid crystallising out being roughly two-fifths of the weight of carbohydrate used and that of sodium mesoxalate about one-tenth. There are, however, considerable differences in the temperatures at which the initial violent reaction starts and in those reached during this action, but otherwise the procedure and results are much the same. Hydraxones of iMesoxalic Acid. The hydrazones of mesoxalic acid are easily madc by dissolving sodium mesoxalate in warm water, adding the equivalent quantity View Article Online

THE OXIDATION OF SUCROSE BY NITRIC ACID. 3707

of the hydrazine dissolved in acetic acid, and heating for a few minutcs until the solid which is first formed and which appears to be a sparingly soluble hydrazine salt of mesoxalic acid dissolves and a clear liquid results. On cooling and adding excess of hydro- chloric acid, the hydrazone of mesoxalic acid separates as a bright yellow solid. FIG. 1. Published on 01 January 1922. Downloaded by North Carolina State University 09/12/2014 09:52:42.

I. Mesoxalic acid p-chlorophenylhydrazone. II. Mesoxalic acid 2 : 4dichlorophenylhydrazone. 111. Mesoxalic acid o-chlorophenylhydrazone. IV. Mesoxalic acid p-tolylhydrazone. V. Mesoxalic acid phenylhydrazone. VI. Mesoxalic acid o-tolylhydrazone. When these hydrazones are heated, they melt with decomposition at temperatures which vary within very wide limits according to the time taken in heating. The actual melting point of any specimen therefore depends on the duration of heating, and to be of any use as a criterion of purity the time of heating as well as the temperature at which liquefaction occurs needs to be given. In order, therefore, to obtain comparable results the hydrazones View Article Online

2708 TEE OXIDATION OF SUCROSE BY NITRIC ACID. were kept at a number of constant temperatures in the neighbour- hood of the melting point, and the time taken before melting at each particular temperature was noted. Melting-point tubes of about 1 mm. internal diameter were filled to a depth of 5 mm. with the powdered hydrazone. At first a rough reading was taken to give an idea of the temperature requ!red. A tube containing the hydrazone was then placed in an oil-bath at the particular temperature and simultaneously a stop-watch was started which was stopped at the moment when the hydrazone melted. Three observations were made at each temperature and the mean taken. The lowest temperature at which observations were made was in each case that at which the hydrazone would remain during three or four minutes before melting. The curves in the appended figure show the results. In the case of the bromohydrazones, the points of melting were not sufficiently well defined to be worth recording. The arylhydrazones of mesoxalic acid are all yellow, well-crystallised compounds, moderately soluble in hot organic solvents such as alcohol, acetic acid, and chloroform, but sparingly soluble in boiling water. Mesoxalic acid p-chlorophenylhydraxone,(CO,H),C:N*NH*C,H,Cl, crystallises in bright yellow, elongated prisms. If it is kept at a constant temperature of lSG.5", it first shrinks and then melts in one minute. If placed in a bath at 186" and moderately rapidly heated, it melts with decomposition at 192-193" (Found : C1 = 14.67. C,H,O,N,Cl requires C1 = 14-62 per cent.). -Mesoxalic acid o-chlorophenylhydraxone crystallises in bright yellow, elongated prisms. If it is kept at a constant temperature

Published on 01 January 1922. Downloaded by North Carolina State University 09/12/2014 09:52:42. of 175", it melts in one minute. If placed in a bath at 175" and heated moderately rapidly, it melts with decomposition at 152" (Found : C1 = 14.35. C,H,O,N,Cl requires C1 = 14.62 per cent.). Mesoxalic acid 2 : 4-dichlorophenylhydraxone, (CO,H),C:N*NH*C,H,CI,, crystallises in bright yellow, elongated prisms. If it is kept at a constant temperature of 182-5", it melts with decomposition in one minu€e. Placed in a bath at 182.5" and heated moderately rapidly, it melts with decomposition at 188" (Found : C1 = 25.42. C,H60,N,C1, requires c1 = 25.60 per cent.). Mesoxalic acid p-brornophenylhydraxone, (C0,H)2C:N*NH*c6H4Br, crystallises in bright yellow, long, slender prisms. When heated, it shrinks, turns brown, and decomposes without previously melting (Found : Br = 27.74. C,H,O,N,Br rcquires Br = 27.84 per cent .). View Article Online

THE DIAZO-REACTION IN THE CARBAZOLE SERIES. 2709 Mesoxalic acid 2 : 4-dibromophenylhydraxone, ( C0,H),C:N*NH*C,H3Br2, crystallises in bright yellow, very much elongated prisms. When heated moderately rapidly, it melts with decomposition at about 205" (Found : Br = 43.56. C,H,O,N,Br, requires Br = 43.68 per cent .). Mesoxalic acid p-tolylhydraxone, (CO,H),C:N*NH*C,H,Me, crystallises in pale yellow, short, flattened prisms. If it is kept at a constant temperature of 170.5", it melts with decomposition in one minute. Placed in a bath at 170-5" and heated moderately rapidly, it melts with decomposition at 178" (Found : C = 54-13; H = 4.57 ; N = 12-82. C1,HloO,N, requires C = 54.04 ; H = 4.54 ; N = 12-61per cent.). Mesoxalic acid o-tolylhydraxonecrystallises in bright yellow, slender prisms. If it is kept at a constant temperature of 163.5", it melts with decomposition in one minute. Placed in a bath at 163.5" and heated moderately rapidly, it melts with decomposition at 171-172" (Found : C = 54-33; H = 4.64 ; N = 12.5. C,,H,,O,N, requires C = 54.04; H = 4.54; N = 12.61 per cent.). THE QUEEN'S COLLEGE, OXFORD. [Received, October 24th, 1922.1 Published on 01 January 1922. Downloaded by North Carolina State University 09/12/2014 09:52:42.