INTERACTION OF SODIUM HYDROXIDE AND BENZALDEHYDE. 1155 THE reaction be tween benzaldehyde and cnus tic alkdis, as employed for tlie preynrtition of benzylic alcohol, is represen ted by tlie well known eqmtt ion : ~ C ~ I ~ ~ * C H O + N a O I ~ = C ~ ~ € ~ * C H ~ ~ ~ ~ +C,IC,*COONa. Caustic potash is generally employed in the preparation in preference t o c:tiistic soda, according to the inethod detailed by E. Ileyer (Ber,, 1851, 14, 339-1). In the course of soiiie experiments on condensation products of benzaldehyde in pmsence of siunll quantities of alkali, i t wits observed t h a t a n immecliate flocculeiit xiicl bulky precipitate is produced on tile addition of .z concentrated caustic soch solution t o benzttlcleliycle. 'J'he sudden nature of the change, which is accoiiipaiiied by a distinct rise in ternperat&e, indicated the p o d b i l i t y of an intermediate stage in the reaction, and a series of eq)erinients were accordingly carried out with the view of isolatiug, or otherwise provi~ig the presence of :in intermediate compound.The results Ixtve not led to tlie isolation of such a compound, but we have obtained satisfactory indirect evidence of the formation of a n intermecliate ortho-derivative, analogous to t h a t described by Claisen (Be?*., lSS7, 20, 646) as tlie product of the action of sodium methoside on benzaldeliycle. When sodium methoside reacts with benzaldehyde, a white, bulky solid is formed which, when decomposed by water, yields sodium benzoate and benzylic alcoliol, just as benznldehyde does with caustic alkali.If, however, the solid product is first treated with glacial acetic acid and then with water, benzylic benzoate, benzylic alcohol, and methylic benzoate, with only a trace of benzoic acid, are obtained. This1156 KOHN AND TRANTOM: THE INTERACTION 05' result is attributed by Claisen to the formation and decomposition of an intermediate ortho-compound, /ON% \O* CH,* CGH, CGH,* C-0. CH, Such cz compound would be immediately decomposed by water into sodium benzoate, benzylic alcohol, 'and inethylic alcohol, whilst of itself it can brexk down either into beuzylic benzoate and sodium methoxids, or into sodium benxyhte tinil methylic benzoat,e. It is on the formation of an analogous benxylic compound tliilt Cllnisen has based his excellent mekhod for the preparation of benzylic beiizoate (Zoc.cit., p. G-19). The results of the following experiments prove that, in the absence of water, or in the presence of an excess of benzaldehyde, benzylic benzoate is EL product of the action of sodium hydroside on beimildehyde. Its formation may be due t o the action of benzylic alcohol on sodium benzoate in presence of the glacid acetic acid used for decomposing the first product of the reaction, o r to benzylic benzo:ite itaself being the initial producl of the reaction, or finally to the decomposition of an intermediate ortho-compound. To test the first possibility, sodium benzoate and benzylic nlcohol weve heated together in g1aci:tl acetic acid solution for 4 hours, hut the whole of the original products mere recovered without the formation of any benzylic benzoate.When benzylic benzoate itself is treated w i t h caustic soda under the condi- tions employed in the action of the alkali on benzaldehyde with subse- quent decomposition by water, tlie hydrolysis of the ester is incom- plete, whilst benzaldehyde is coinpletely converted into the alcohol and acid by the theoretical quantity of cnustic so& a t the orclinary temperature. Further, if the estcr be the original product, it should be present, irrespective of wliether the presence of an escess of aldehyde or the absence of water is a condition of the reaction, and this is not the case. The formation OF an intermediate ortho-com- pound is the remaining possibility to explain the production of the ester, and the experimental evidence is ~vholly in favour of this view.From this standpoint, the action of cnustic soda on Lenzaldehyde takes the following form : In presence. of water, decomposition into benzylic alcohol and sodium benzoate, the ordinary products of the reaction, will occur : H C,H,*COOPu'a + C,H,*CH,OH + o - + H,O. C,jH,* C-ONn /OH \O*CI-I,* C,H, HSODIUM HYDROXIDE AND BENZALDEHYDE. 1157 I n the absence of water, two decompositions a r e possible : ONa / -...~. I, C,H,*C;iOjLI = O,,H,* COONa + C,H,* C€€,OH, CH, C,;H, . . . . . . . . , /iO EL- Ir, c,~,. c.-o:N~ = c,H~* COO+CH,*U,~I~, + N~OH. \\ ... . O*CH,* Cf,I$', The first decomposition takes place far more readily thnn the second; it is favoured by ail excess of alkali, wliilst an escess of aldehyde favours the latter : facts which corroborate this view of t h e reaction." The experimental results shorn that Nef's suppositions (AwnnZen, 1597, 298, 301) in regard t o the course of the reaction between benz- aldehyde and c:~ustic alkalis are iiniiecessary, and they bring t h e change into line with the analogous reactions studied by Chisen.There are two ways in which the aldehyde gronps of 2 molecules OF benzaldehyde can give rise t o the formation of condensatiou products. One of these is t h e well known benzoin condensabion, the other should lead to tlie formation of benzylic benzoate, thus : Eoi y l i c I/cth:oc& condc:iioccficn. The latter change, however, as shown in the following esperiments, takes place only as the result of the formation of a n intermediate compound, and it is probable that the production of an additive com- pound also precedes the benzoin condensation. This point is under investigation, especially with respect t o the use of dry materials i n the reaction.* In a reccnt paper by Hallcr 011 compoiinds of cainplior with alcichycles (Con@. m i d . , 1S99, 128, l2i0), the forniation of piperonylic piperonnte by the action of piperonaldehyde on sodium camphor is attribnted to the l~rcsence of sodiiiin borneol in the niixtnre ; since, however, caustic soda is liberated in the forination of the condensation product, piperonylidcnccniii~~lior, which is the chief product of the remtioii, i t appears extremely probable that tlie formatioii of piperonylic piperonate, which is accoinpanid by some piperonylic nlcoliol, is redly clrie to the action of the liberated alkali on tlie piperonaldehyde.If so, the formation of the ester is an interesting coiifirinntioii of the above vie\\ of the i l l teractioii of aldehydes and caustic alkali. In a lirevious paper (Cutript. rc)2(2., 1S91, 113, 22) on the sanie subject, caniphylic salts of the acids corresl~onding with the aldchycles employed are described as secondary products of the reaction and their formation is accounted for on the lines of the reitctions studied by Claisen.1158 KOaN ANb TRANTOM: THE INTERACTION OF There is one other possible course for the reaction between benz- aldehyde and caustic soda, namely, that the two molecules of aldehyde condense directly to an unsaturated glycol : ‘(iHb* $*OH This repre- C,I-I,* C*OH’ sents a tautomeric form of benzoin, the dibenzoyl and dincetyl deriva- tives of which are known, but no indication of the foriiiation of such a compound or of its derivatives wns obtained. It could yield benzoic acid and benzylic alcohol very simply, thus :- C,H,*C*OI-I + ff2 = C,H j* CI€,Ol-I C0HG C 0 H 0 C,H,* CO*OII but the formation of benzylic benzoate from it would not depend on the absence of water, or the presence of an excess of aldehyde.EX P E 11 111 EN TATA. A c t i o n of Ccczcstic Soda O?L L’e?azxakleAp2e i ~ b Prescizce of TVuter. 9 number of esperiments were first tried in wliicli an aqueous solutiou of sodium hydroxide was added to benznldehyde in the pro- portion of one molecule of the former to two of the htter. The precipitate that is formed immediately, iiicrettses in bulk rapidly on standing, and the reactioii may he completed eitliev by heating the mixture on the water-bath for 3 hours, or by allowing it to stand, with repeated shaking, for a day.To 53 grams of benzaldehyde, 10 grams of caustic soda dissolved in 15 grams of water were added. The fiual product consisted of a hard cake, which was dissolved in 75 C.C. of ~varm glacial acetic acid, and the solution diluted with mnter, made alkaline, and extracted with ether ; the oil oltained by evapor ation of the ethereal solution was then fractionated. The alkaline solution mas acidified and the precipitated benzoic acid collected, Under these conditions, beiizylic alcohol and sodium benzoate proved to be the sole products; it is a matter of indifference, therefore, whether water or glacial acetic acid is used in the decomposition of the final product of the reaction.The yield of benzylic alcohol under these conditions is extremely good, 90 per cent. of the theoretical yield being obtained, and by in- creasing the proportion of sodiuiu hydroxide to 30 grains, ti theoretical yield (0s per cent.) resulted. This is consequently n better, as well as EL cheaper, methsd for the preparation of benzylic alcohol thnn that usually employed. Action of Solid Ccczcst ic S‘ocla OIL Bema Idel@. 10 grams of caustic soda were ground to a fine powder undei benzene, washed into a flask with benzene, and a solution of 53 gramsYODIUhl HYDROXIDE AND BENZALDEHYDE. 1159 of benzaldehyde in 100 C.C. of benzene added.During the addition, the mixture was well shaken; after a short time, the whole set to a hard mass. This was heated in a reflux apparatus on the water-bath for 2 hours, the mass being broken up and shaken several times during the heating. Tho solid residue was ground up in one case with ether, and in another with benzene, the extracts filtered, and the residues fractionated after distilling off the solvent, but iu both cases only benzylic alcohol together with some unchanged benzaldehyde was left, the yield of the former amounting to 76 per cent. of the theoretical. , In these experiments, no special care had been taken to render the materials anhydrous, lout the necessity of this condition became ob- vious when the structure of a possible intermediate product was taken into account.As shown on p. 1157, a inolecu1:tr proportion of water ie regenerated in the action ; this, therefore, will suttice to effect the complete breaking down of the compound into benzylic alcohol and sodium benzoate. I n the subsequent experitnents, the caustic soda was first ground up under benzene to prevent undue absorption of moisture during the grinding, the greater part of the benzene drained off, and the rest removed by drying in an cxsiccatoi*. The final drying was effected in a vacuum over phosphoric oxide repeatedly renewed. Only small quantities of caustic soda, spread over a large surface, were dried at a time. The benzene employed as solvent was distilled over sulphuric acid and phosphoric oxide successively. Two ex- periments were made with materials thus prepared.In both cases, the mixture became solid very soon, athough in one (No. 11) the aldehyde was added very gradually, and the temperature kept down by means of ice previous t o the heating on the water-bath. The product of the reaction mas first dissolved in glacial acetic acid, the solution diluted with water, and then extracted with ether aftor the addition of alkali. The following are the details of these two ex- periments, 200 C.C. of benzene being used in each : 11 *5 10.01160 KOHN AND ~ R A N ~ O M : THE INTERACTION oli’ The presence of unchanged benzaldehyde in both cases is due to the difficulty of effecting a complete reaction in the solid mass, although it was broken up and thoroughly mixed several times during each experiment, Claisen obtained from 10 to 40 grams of benzylic benzoate from 106 grams of benzaldehyde by the action of sodium methoxide.It therefore appears that tlie methylic ether of the ortho-compound breaks up somewhat less readily than the simpler derivative into the alcohol and acid (methylic ester), The benzylic ether is still more stable in this respect. The benzylic benzoate boiled at 280-320°, and was therefore accompanied by some benzylic alcohol. &ref idly fractionated, it yielded a product boiling at 310-330°, which gave the following results on analysis : 0.2089 gave 0.6074 CO, and 0.1 132 H,O. Pure benzylic benzoate was found to boil at 316*S”, as determined by an Anschiitz thermometer with its stein immersed in the vapour (Claisen gives 323-324O).That the product was benzylic benzoate was confirmed by hydrolysis with alcoholic potash, when benzylic alcohol and potassium benzoate were obtained. c! = 7930 ; H = 6.09. C,,H,,O, requires C = 79.35 ; H = 5.66 per cent. Action OJ Caustic ) b d a on an Excess of Benxdclelyde. 111 the above experiments, the theoretical quantity of caustic soda required by the equation was emploFed. I n order to obtain a condition more favourable to the decomposition of the ortho-compound into benzylic benzoate and caustic soda, an excess of benznldehyde was used with which the liberated alkali might react until tlie decomposi- tion mas complete, The results and conditions of this series of ex- periments are tabulated below. The formation of benzylic benzoate when an aqueous solation of caustic soda was used, is ;I most satis- factory proof of the formation of the intermediate ortho-compound.With dry solid caustic soda, it mas found estremely difficult to complete the reaction, since the mass cakes together mid the excess of aldehyde thus largely escapes further action. This is doubtless the reason mhy the extent of the decomposition as well as the quantity of ester found as the product of tho decomposition is not greater. The alkali was not always added at once, being sometimes introduced in portions at intervals of several hours. I n all cases, the mixtures were heated on the water-bath for t,he times stated, and the products of decomposition worked up as described above.SODIUM HYDROXIDE AND BENZALDEHYDE. experirnent,s I 6 22 20 31 27 and 11, the total decomposition cori esponds approximately to the maximum for the quantity of caustic soda employed, but in experiments 111, .CV, and V? carried out with dry materials and solid caustic soda, only from 30-50 per cent.of the total decomposition lins been effected. Action of Caustic Soda O I L 13e1~x~lic Bemoate. If the supposition is correct that an intermediate ortho-compound is formed in the action of caustic Bocla 011 Lenzddehyde, the same pro- duct should result when benzylic benzoate is treated with caustic soda. 26 grams of benzylic benzoate, dissolved in 100 C.C. of benzene, were treated with 5 grains of dry solid caustic sod:L. No appreciable action took place until the injxture was heated on the wltter-bath, when, after 6 hours, the whole became nearly solid. The product was dissolved i n water and examined, with the result that altogether 20 grams of sodium beiizoute and benzylic alcohol mere isol:tted, 10 grams of the ester remaining unchanged, thus proving that benzylic benzoate is not the initial product of the action of caustic socla on benzaldehyde.Action of lSoclizcni Benz&zitle on Be~izctkdekyle. 4.6 grams of sodium were dissolved in 21.6 grams of benzylic alcohol in 125 C.C. of benzene, and 43.8 grams of benzaldehyde were added graclually. After shaking, the mixture was heated on the water-bat11 for 16 hours, the solid residue dissolved in water, estracted with ether, and the residue froin tho ethereal solution fractionated. benzoic acid was separated from the alkaline solution by the addition of hydrochloric acid. The following products were obtained : Unchanged aldehyde ............... nil. Benzylic alcohol ................... 18 grams. Benzoic acid ........................ 8.5 ,, Beiizylic benzoate .................. 29 ,,1162 BLYTH : TXE ULTRA-VIOLET ABSORPTION SPECTRUM OF I n this case, therefore, despite the direct addition of water, decompo- sition into the ester proceeds to the extent of 54 per cent., and that int.0 benzylic alcohol and benzoic acid only to the extent of 46 per cent. of the theoretical ; the forination of these products, however, is a satisfactory confirmation of the correctness of Claisen's view. Also the relative staldity of the met,hyl and benzyl ethers of the ortho-compound, as regards their decomposition into esters, is quite in accord with the influence of these siibstituting groups. The decomposition of this benzyl ether by water into benzylic alcohol stid sodium benzoate is represented by the equation : The foregoing results lead naturally to the study of the influence of water in several reactions involving the use of alkalis, such as the two decompositioiis of ethylic aoetoacetate and allied changes ; also t o the complex action of alkalis upon aliphatic aldehydes. These sub- jects, as also the action of alkalis on other aromatic aldehydes, are now under investigation, LIVERPOOL. UNIVEMITP COIITJEOR,