Some anomalies of the Schiff aldehyde test
Item Type text; Thesis-Reproduction (electronic)
Authors Tolley, Willis Brown, 1926-
Publisher The University of Arizona.
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Link to Item http://hdl.handle.net/10150/319208 SOME ' AKOIfiALIBS OF THE SCHIFF • ALDEEIDE TEST
V by -
mills ' B./ ;Tolley
• A Thesis - - ■' _ . . submitted to the faculty of the
Department of Chemistry in partial fulfillment of the requirements for the degree of
MASTER; OF '.SCIEHCE in the Graduate Colleges University of Arizona •
1951
Approved Director of Thesis Date
" Y 'f S f . ; V
' ■: The author expresses his sincere appre
•. elation for the ever available ass is tanc e
’ and guidance- of Dr.' H. D. Rhodes* TABLE OP CONTENTS
'MTRdLTBTlOE-^ _ ' o - ■ « « . « »;■:>;= 1 ■ : ...woi^k, .on-..tie'sfc' reagent . - o „ = .' » 1 Hngo. SeiixLL & ...' © © © » © © © . © T V/ '0&ro - and Schmidt © © © ' ■■L.'.r'' ■» 1 ;‘ : ■.Hahtsch and 0;stwaId' © - © ^« : © ■ © \ © . © ; y: 1 : ; Bucherer ; ' > ■ © ' © :. » © . © ;© 2 ::y\:;./;_ViFieland’''and Scheuing'© © © »'/ 2
LITERATURE. .SBAEGH ' © . 6 © . ©. ' ; © © © ... ©\ \:© % ; ; .■;.;Pah,i^.;-;dhd'/yon,:'Buttlsir. ©■; © » © - :© ■; 8 L . Schmidt ' '; .y: ■.■■;©. \ © v ° » : © / 9 h; I t- Bela foh Bitto .© ' ©: =; ' © ■■ «' ■ ' ©"'..L© © ;: ■;' 9 . norenz © © © © © * © © © © © 10 -' Shoe smith, Sossen,, Pletherington© © © -:t 11 :.. ..Lieon . ' © © . © © ©. © \ © . .©. > ; .14'■ jBXPERllBNTAL ;:.'© ■ * . © : © © © - v© © ■ 17 vXAld.ehyde Synthesis. © .» © © « © © : » ' 17 '2 9 5-Dihydroxybenzaldehyde (G-ent is aldehyde j © 17 -: % Oeheral Reaction © . © © » ». « 18 - . . Preparation^ of Zinc Cyanide . . ©. ■•.© © 19 7; - Preparation of 2 ,4=dimethoxybenzaldehyde © © . Re sore aldehyde dime thyle ther} © © © ' 20 Orcinol Aldehyde © © . . ©: © © 21 7 : 2S5,4“Trihydroxybenzaldehyde (PyrogalloL ■■. .. Aldehyde) ■. © ;© ©. © © © - © • © A2 v Preparation of 4™Hydroxy-2-riaphthaldehyde ' . . ( a-Haphthol Aldehyde) © . ©' © 'o'.©. 23 ' ..' ' Preparation of 2-Hydroxy-l-naphthaldehyde V. h/ . " 7 ,(B=Naphthol Aldehyde) © © © » : 24 I 1 .Preparation of 2,4,6=Trihydroxybenzaldehyde © (Phloroglucinol Aldehyde)« »' • © © © . 25 .Preparation of 2,5-Dihydroxybehzaldehyde ; I . (Gentisaldehyde,) . © © © ... » © . . . 26 Preparation of 2,3-Dihydroxybenzaldehyde .- . - , (Catechol Aldehyde) © © ©I . © © 27 PREPARATION OP REAGENT . © © © © © ■ © 28
1THE: SCHIFP ,TEST PROCEDURE y . © . . © © © 30 - TEST RESULTS > . ‘ ^ ^ v vt- ' '’ c. V > ". '.M-
discussion. » .■' x o . y, :'- > . 39 . STOMARY OF RESULTS; - -o';. .. . 45 CONCLUSIONS o ■•. .;■ ' o/; o ’ o ' o o o „ I 47 ' : BIBLIOGRAPHY . -V'- . " . . I,. ■49,. ABSTRACT o, '■ / ' •« ' » y'- o - o ' Vo-.. v ,. : o - 51 INTRODUCTION
■ ^ e ;‘Sch.iff :..tesi|.:/’^'3P;vaiaehy An incorrect interpretation of the nature'of the fuchsin sulfurous acid and "the structure, of the . dye which it forms : - . ' ‘ - - ' ' - , - . (8) With aldehydes was.proposed by Schiff« Not until 1900 • . when Hantsch and OstWald published a paper concerning the relation of the'colored salt to its carbinol derivative had .;v any-further Investigations been carried on in this field® Hantsch and OstWald were Of the opinion that the alde hydes facilitated the splitting off of sulfurous acid from •. 2 tti.e'i'leucQsulf onic aoiS wliiDh. led to - the. reversion of the 1 fuchsin to the quinoid'structure$ the aldehyde then condens- : : lhg with'the fuchsia under the influence of sulfurous acid» .. ' Durrschnabel and Whil^^ ohtaihed a free sulfonic acid by introducing BOg into a suspension of par ar os aniline, in a ' i- : little water» Bucherer ^ was of the op ini on that the aide- • v hyde accumulated on the sulfo groups, resulting -in a rearrange- v;^hht-. within, the .itiolecule .which caused a reversion to the quinoid structure with the splitting off of the remainder of the aldehyde sulfurque acid from the carbohe," In' 1921 Wielahd ahd Scheuing^ ^ realized the need of , ' % clarifying the structure of the fuchsin sulfurous acid in order'to establish the etructure of the dye in the aldehyde reaction. 'Their -experiments prored. that Hanfsch; and Ostwald did hot fully, comprehend the part played by thesulfurous • acid in the reaction. They convincingly show that the colored 16 neutral sulfite58 is not a salt of sulfur ous acids hut is actually the parafuChsih salt of parafuchsin leucosulfonlc. acids only half as rich in BOg as the "acid sulfiten, If the combining ability of the NHg group in primary amines is considered, it is quite easy to see the difference between the two sulfonic acids. RNH * S0P ------> • RNS0oH 2 ^ * Primary amines add SOg to form aminosulfinic acids which are soluble in water as free acids. Under these con ditions paraleucoaniline will dissolve easily in SOg with a yellow color. ■Eiae C=sulf onlc . acid cannot be isolated due to the loes of . tlie . SOgH grpup. as sulfnrous acido However, the 80g group., bound to the HHg can be .easily differentiated from the C= V bound sulfo group since it is completely removed by iodine» The splitting off of the C=-sulfonic acid group takes place' ■ less readily with the. di-M-sulfinic acid of paraleucoanilineo At this time it had not been definitely ascertained that the dye contained SOg at all, or whether the dye was identic . eal to. that produced from a reaction of fuchsin with one or m two 'moles.: of the aldehyde„ ' A. direct condensation of the alde hyde with parafuchsin shows a different; shade of color and". - forms compounds with differenf solubilities than the. dye in the Schlff .tests and.therefore Such a possibility must be eliminated« The dye of the reaction has not been isolated and seems to exist only in the dissolved state due to its •Instability® ' Its composition "and.nature have - been determined through a colored by-product of fuchsins SOg and the aide- : ' hydef.:: " . ■ " Vif--' i-• p;' " ■ ;. .Parafuchsin mixed with one mole of.SOg and one mole of ' aldehyde.forms a bluish-red dye almost immediatefy® Fuchsin '" ■'reacts -slowly with the aldehyde and is incapable of reaction : with the aldehyde sulfurous acid* Since the parafuchsin're acts • almost immediately with SOg, forming a sulflnic acid which in, turn reacts with aldehyde* the reaction must unmis takably go in this manners giving a dy'e of the fo 1 lowing : structure® . .. ,- ' . ■ ", 5 Actually the dye is not the fuchsin-imine derivative as shown, but exists in the form of an inner immonium salt. 6 The addition of excess sulfurous acid changes the dye from the quinoid to the benzenoid structure forming a crys talline compound, the leucosulfonic acid of the dye. This compound, being quite insoluble, separates out of a concen trated solution. OH H2N N-S-O-C H HCH K H2S03 Excess v i -0 SC-zH H H 2 OH H, +Y N-SO-CH ■'C HCH H KK, However, the true color recognized as the dye in the Schiff test does not form until another mole of SOg reacts with the parafuchsin base by means of an NHg group. The sul- finic acid formed in turn reacts in a greater concentration of aldehyde in the aforementioned manner, forming the di-alde hyde sulfurous acid linkage. With this second addition of aldehyde which fixes the N-sulfinic acid remaining in equilibrium with the insoluble compound, the C- bound sulfo group is no longer strongly held. Even in excess sulfurous acid, HgSOg is lost and the molecule returns to a quinoid structure. The resulting -colored compound is the blue-red dye formed in the Schiff 8 H Pauly and von Buttlar^^ have Indicated the failure of the test with 4-hydroxy; 2,4-dihydroxy; and 3,4-dihydroxy- benzaldehydes• The two monohydroxybenzaldehydes, 2- and 3-, are said to give a fairly strong test. Gentisaldehyde, 2,5-dihydroxybenzaldehyde, gives a strong test, while o-van- illin and solutions of the two other vanillins, 3- and 4-hydroxy, react weakly. From their experiments Pauly and von Buttlar generalize that: 1. Ortho hydroxy-substituted aldehydes react better than para-substituted compounds. 2. The dihydroxybenzaldehydes in general react more poorly than monohydroxybenzaldehydes. The authors used the following procedure in testing: One tenth gram of aldehyde was dissolved inScc of water and treateci with 5 cc of fuehsin;-sulfurous acid solution. For all dihydroxyhenzaldehydes one cc of chloroform was added! fhia was to concentrate the dve ' formed/ giving a better estimate of the color. h . ( 19 ) • . - ' . ' t- Schmidt • tested a group' of aldehydes and a large number of other, compounds ^ some few of which he reports as : giving - the aldehyde test. Of: the . aldehydes tested $, cuminalde ;hyde: gives a test only af ter shaking and einhamaldehyde at first gives a bright;yellow- color which later turns red. - Bela von Bitto^^^ .has tested a large group of compounds with the Schiff reagent® : His reagent was prepared according to the directions given by Schiff® "In a liter of water 0o25 grams of fuchsin were dissolved and then sulfurous acid was passed in until it was decolorized®'i- : - 1 . von Bittb reported-good color reactions •tpoh place with • the aliphatic aldehydes/ but the. aromatic aldehydes reacted with different degrees of color intensiby~p., depending on the hypelof substitution®:ihh';^I' , .1/h; • ■ ' ■ Aliphatic Aldehydes , ' : ; / Formaldehyde • .■ Immediate color Acetaldehyde, ’ ; .: ^ Immediate color . ‘ Bar aldehyde . ■ Immediate color; but weaker, ll-lh .. • than with formaldehyde. 10 ■ ' r-'I - Aliphatic -Aldehydes (Contlhme&) • : -- . ■ ’ 'Aldehyde ammonia , / '.Immediate color but weaker ;V vthan with' formaldehyde Monochloracetaldehyde. ' . G-radually' appearing color Isohutyraldehyde . Gradually appearing color Butyl chloral { Gradually appearing color ' ; Crotonaldehyd©: ;.;-':;lmmediatekeolhr.::;yA '- : I • llgllc ■aldehyde. - - ' Immediate eolpr' ;v ' Methylethylacrolein / > ' ^Gradually appearing color . . Furfural . .. . Immediate but weak, color .. Aldol ., 1- ■ 'Immediate color - I ; . I ::;-^ ■ Aromatic Aldehydes ' ; . ; . ' Benzaldehyde Immediate color; Ginnamaldehyde. . Bright$ but slowly appearing Cumina! (cumic or ."/Very weak^ very slowly appear- ' cumlnlc aldehyde) : ■ hhg color . - . v ;'c . . •;..... ■ Anisaldehyde i ; > d; Immediate but weak color _ ■ 'lanillih: . I • . d Gradually .appearing«, very '. - : . Weak reaction . ' . - ' p-Homosalleylaldehyde ._ ; H . . / d •p-Nitrophthaldehyde . ho color . ; . 1 Anisaldehyde" is reported a's giving a yellow color at firsts whi ch turns violet as was.indicated by - Schmidto Lorenznoticed that piperohal treated with a solution of rosaniline which has been decolorized with sulfurous acid 11 : •■-■■glares a deep yellow dyes tuff which changes over to blood red in a short time* ■ " ■ ; " ' i" ■ '• ■ ' "■ : : --v V ' '' • Shoe smiths Sossen^ and Hetherington^^^ have, tested a : ■: .large group of aldehydes with fuchsin sulfurons.■ acid» It was their hope to determine the cause of the abnormalities observed in the test with certain aldehydesc They reported the reaction product to depend chiefly oh the. quantity of : • sulfur dioxide capable of neutralizing iodine.(afterwards i referred to as “free sulfur dioxide11) ■- "■'h f ' i - i ' ■ i. . . .. 12 In the table below the letters have the following sig nificance : Y - yellow B - brown 0 - orange Sub P - precipitate R - red Sub C - coloration P - purple g - grams of free sulfur dioxide per 100 cc of reagent. Free sulfur dioxide per 100 cc of reagent 19 10 1.0 .25 .1 salicylaldehyde Pc pp YP YPYP p-hydroxybenzaldehyde pc pc pp YP Yc b-resorcylaldehyde pp YPYPYPYP dihydroxyisophthaldehyde Rp YP YP YP YP 2,3,4-trihydroxybenzaldehyde Yc Y c Y C yc Y c p-methoxysalicylaldehyde RP R='YP YP YP YP vanillin PP BP YP YP YP orcylaldehyde RP YP YP YP YP a-orcindialdehyde RP YP YP YP YP indole-3-aldehyde RP YP YP YP YP 2-hydroxy-3-methylbenzaldehyde RP YP YP YP YP 2-hydroxy-4-methylbenzaldehyde RP YP YP YPYP 2-hydroxy-5-methylbenzaldehyde Y RP YP YPYP P 2-hydroxy-l-naphthaldehyde °P Op op Op °P o l-hydroxy-2-naphthaldehyde R O 0p °p y 0P °P c innamaldehyde pp PP PP BP Bp 13 The following aldehydes were found to behave normally with the reagent under all the above conditions: benzaldehyde 2-nitro-4-methoxybenzaldehyde m-hydroxybenzaldehyde 3-nitro-4-methoxybenzaldehyde o-methoxybenzaldehyde 3,4-methylenedioxybenzaldehyde m-methoxybenzaldehyde isopropylbenzaldehyde p-methoxybenzaldehyde 2-carboxy-3,4-methylenedioxy- benzaldehyde o-nitrobenzaldehyde a-naphthaldehyde m-nitrobenzaldehyde 3-methoxy-a-naphthaldehyde p-nitrobenzaldehyde 5-methoxy-a-naphthaldehyde o-chlorobenzaldehyde 5-bromo-a-naphthaldehyde o-fluorobenzaldehyde 5-bromo-2-naphthaldehyde m-fluorobenzaldehyde acrolein (deep blue) m-bromobenzaldehyde isobutyricaldehyde p-bromobenzaldehyde glycollaldehyde p-methylbenzaldehyde glyoxal The 2,4-dimethoxybenzaldehyde, 2-methoxy-l-naphthalde- hyde and thioacetaldehyde were neutral toward the reagent, while b-resorcaldehyde reacted very rapidly. Although the authors1 meaning is not clear, this presumably means that these compounds gave no reaction. Shoesmith, Sossen, and Hetherington conclude that the o-hydroxy aromatic aldehydes give the yellow precipitate most readily. However, exceptions to the rule were observed in the few following compounds. 14 p-hydroxybenzaldehyde (when only a trace of free SO^) vanillin c innamaldehyde indole-aldehyde In 1932, Li son published a long paper, 11 On the Spe cificity of the Reaction of Schiff Toward Aldehydes,” in which he attempted to show the non-specificity of the Schiff reag ent toward aldehydes. Although he has tested over 400 com pounds, most of which are non-aldehydes, and reports in a great many cases that these compounds do give a color test which cannot be distinguished from that given by aldehydes, the present writer feels that much of his work can be ques tioned. The Schiff test, if carried out intelligently, real izing the limitations which must be placed on it, can be used with considerable success in classifying aldehydes. Lison states that isoeugenol reacts readily with fuchsin sulfurous acid while the aldehyde (vanillin) which is derived from it by oxidation reacts-much more feebly. H P=c -c h 3 OH Isoeugenol Vanillin 15 Isosafrol likewise reacts readily while the aldehyde which is related to it (piperonal) does not react at all. H H 0 C-C-CH^ c - H - '? \ /Vi X°-ch2 xo .6h 2 Isosafrol Piperonal Articles such as these indicate that there is a definite limitation to the Schiff reaction. Since the test is cited as giving poor results with several of the monohydroxyben- zaldehydes and dihydroxybenzaldehydes, there may well be many other aldehydes of similar structure which will give an anomalous test. It is the aim of this investigator: 1. To test a number of aldehydes and other compounds that have been questioned in the literature using what ap pears to be the most delicate Schiff reagent composition. 2. To determine whether or not the aldehydes reported as giving anomalous results actually do so with the most sen sitive reagent. 3. To determine whether or not aldehydes that give anomalous results also give sufficient characteristic color to allow their recognition as aldehydes. 4. To discover some generalities, if possible, by which : 1 6 . one can predlot- which.oornpotmds might- be" expected to give anomalous results o ; : ::: .. . - : ■ .So To repeat some of the more questionable worksv:wh±bh - report.anomalies and thus.confirm or deny them, 6» - In-"shorts,"\:to ,.define more •cTearlv :the area .In which ■ 0 anomalous results may he expected and -to - establish more defin itely the limitations which must he 'recognized- for the Schiff: test. : ■ ' - ;,' V -v- ' ; ' ■ . : .: \ ./ ‘ /d - EXPERIME1TAL R;.: : : ^ ;v AmBHM SYETHiSIS ; Ry gy 5~DxhydroxybenzaIdehyde (Gentisaldehyde) ' The preparation of gsB-hydroxybenzaldehyde was first . attempted by the Reimer -TIeman reactiono . fhis reactlbn was carried out four times with little suecess, A small . amount uf the aldehyde was formed as the concentrated ether solution became yellow and a few drops of It - turned deep red in basic solutione ^ ^ However the aldehyde could not be re covered o . : ; . . '' -r I ^ G-ent is aldehyde -was finally prepared by a, different pro- cedure») The yield was 18% of the theoretical as compared to a yield of 19%reportedo After recrystallization the , yellow- needles were found to melt at 98°« ' -.-t^ I- The .remaining;-aldehydes, were prepared by the 'Adams- . hevine simplification of the Gattermann;Synthesis■ . 18 General Reaction H H C=N . HC1 ✓OH ZN(CH)o HOI / x ^ O H i------:— > Ether / ♦ HgO HC1 ^0 C — H OH O' Adams and Levine offer the following equation for this reaction: HON + HC1 -----> C10H = NH (formimino chloride) A1CL ArH * C1CH = NH ArCH = NH ♦ HC1 or (I) ZnOl, HgO ArCH -= NH t HC1 ArCHO NH, (I) 19 These authors point out that this explanation of the reaction'Is probably inaccurate= It does3 however$ show the formation of the Intermediate imino chloride (I) which hydro11zes.to the aldehydeo ; 1 ; The Adams modification rempves. the danger of using anhydrous HGH by passing dry HCl into a mixture of zinc cyanide^ aluminum chloride s the hydrocarbon or phenol ether, and a solvent (as benzene or chloroform) or into a mixture - of zinc cyanide, phenol, and anhydrous ether or benzene» Zinc cyanide is converted by the hydrogen chloride into hydro gen cyanide and the reaction then follows the Gattermann re action of 1907o h . I y - ■ V - . Preparation of Zinc 'Cyanide . ■ ' :y;v."The; zihc cyanide was f irst prepared, by the procedure used by Adams = This method proved very poor> invariably 'givlng a gummy produet and very small yields« When this product was used in the aldehyde synthesis a very poor yield was-realizedo The precautions listed were followed closely, but;the zinc cyanide was never satlSfacibry. : , y. An.alternate preparation for the; zinc cyanide was found ( 2 2 ) : ' ■ . - ' V ' . ' : ' • - in Togel-.; This preparation was exceptionally satisfac- toryy giving - an/ almost: quantitative iyield of zinc cyanide. ; The product was found to work well in the Gattermann reac- ■ , I : - V ■ ; In.the prepafatlon o f .the: aldehydes by the Adams-Levine 20 modificatipn of the ' G'attermanri syhthesis $ two procedures .. ; were/ followed* These will be referred to - as General Direc- ' tIons A and General Directions Bo ■ • _ ■ _ The proeedures are basically the same except for the solirehts used and. other slight variations o In procedure A ? sodium, dry benzene i?as used as the solvent and anhydrous ■ aluminum, chloride was- introduced a half hour after the reac tion was started. „In procedure B s sodium dry ether was used as-the solvent and aluminum chloride was omitted* The B procedure was much simpler'to handle.as it did: not involve ■' interrupting the reactiono - ; Preparation, of BgirSlmethoxybenzaidehyde (Resorealdehyde dl° methylether): . ' n . - v/; /; . General Directions A' were followed * ".t.-.v. ■«; A- poor grade.of zinc cyanide was used* As reported by Gattermann^ a gummy zinc cyanide interferes with the reaction giving very poor yields* Unfortunately in this case* all of the resorcinol dimethy1ether was- used in the f irst attempt» yielding only a gram of^the aldehydef The product3 however, was good and melted at 70°G^^o . ; ; % - / . . -In. the course of the reaction an intermediate is formed which is usually" a bright colors in this case red* The red prec ipi tate was hydrollz ed with dilute hydro chloric acid (1-3) .and -the mixture was, steam-distilled, giving a milky emUlsion which Separated out on standing as a yellow oil* 21 ©onsiderable;; difficulty was experienced in crystallizing ; : ; this oily products A bisulfite addition product was made _ ' of one portion* but the best results were obtained by dis-' .'ivy v solving the oil in ligroin -and allowing the ligroin to evap orate to dryness in.-airI In this way9 long, white needles : which melted at 70° were formedThe small yield. Only - ' about 3^ of the theoretical, was attributed to the poor zinc/ cyanides : . V -' '' . v •V. . - Qrclndl; Aldehyde : ' : "■ V ; ■. • ; ■' - V ' ' o ' - : General directions B were fbllowedo V ' ' ' ' - Again •. a; poor grade; of zinc cyanide was used and the . : * yield was. poor= The reaction prpCeeded smoothly with the formation/ of a heavy oil which began to solidify after about 30 minute So ' The precipitate was bright orange in color,; / This ihtermedlate. was- not hydrolized until the. next day* Af =r': ■ ter standing 24. hours the precipitate had turned bright red at the surface in contact^ with the ether-HOP solutlono Very .probably the reaction was; not. complete when the precipitate. - and .ether 'solution were, ^reindved from the- reaction flask, . V : ■ The : imide hydrochloride was hydrolized by boiling Jit . ' 1 , for five minutes, in 100.cc of water. When the. solution .cooled, a dark red solid formed= This product was filtered at the ' pUmp" and repeatedly recrystallized from boiling water using ' : decolorizing carbon^ Decblorizatidn was very slow, the pro™ ; "duct being recrystallized seven times. This may partially . V : ' 22 account for the low yield. The final product formed, in white needles and melted, at 180°c • The yield was only 10%', much lower than that reported by G-attermanno ; 2„3 a 4°Trihydroxybenzaldehyde (Pyrogallol Aldehyde) General Directions B.were followed. The preparation was first attempted using the poor zinc cyanide, . No aldehyde was recovered, 4t this time, the more-satisfactory zinc cyanide was prepared by the method recommended by Vogel, The aldehyde preparation, was attempted the second time with no success, following thiss a second sulfuric acid drying bottle was added to the hydrochloric acid generator and the dry ether was redried over sodium and distilled. Any moisture whatso” . ever seemed to have drastic results, on the yield, . The preparation was .how attempted the third time, The . pyrogallol.was dried ■With zinc cyanide at a temperature of 80°G for fifteen minutes before beingfused in the reaction. The intermediate formed smoothly, s olldifying about forty minutes after the reaction had started. It was a flesh-col ored solidi much lighter than the intermediates of the pre vious preparations, -The imide hydrochloride was hydrollzed: by boiling it with 400 cc of water for five minutesThe , >■ aldehyde separated in a fine, gray, amorphous powder as the solution cobled, A 64% yield was realized3 which 'is con- f - siderably higher than the 45% yield reported.by.Qattermann, 25 .Although the color and physical appearance of the product were poors the melting point was 158°Gl Indicating that the - aldehyde was quite pure„ Using decolorising carbon, the aldehyde was recrystallized twloe/from boiling wateh,lform-. ing fines, slightly yellow needles which melted at 158°C« After this purification, eleven-grams of the aldehyde were . Obtained, constituting a 55„5% yieldo , Preparation of 4”Hydroxy-2°naphthaldehyde (a-Uaphthol Aldehyde) General Directions B were followed. In this trial a smaller ratio of zinc cyanide to phenol was usedo The reaction proceeded smoothly with the formation of .a gray, gum#y product which solidified, after 45 minutes ' • . as a bright yellow solid. This aldehyde, is so insoluble in water that hydrolysis in pure water is •unsatisfactory« As. soon as the intermediate hydrolizes, the aldehyde precipi tates o .Therefore,the imidehydrochloride was hydro11zed'in a 55^, alcohol'“Water so iut ion, '.The hydrolysis proceeded . smoothly with the formation of an amber-colored solution, ,This solution was boiled for five minutes and allowed to;.cool, fhe‘ aldehyde precipitated, Out; in yellowish needles which were .filtered at the pump, After:standing overnight, the filtrate yielded two more grams of aldehyde» . The yield of this crude aldehydef melting point 172°C, was- 24 grams, constituting a ■7S^yieia...y,P ■■■■■: ‘ : , ; .■''l The present'''investigator had little success in, trying . 24 to purify the aldehyde by recrystallization from a 30% aleoV :hol=water solution,containing.decolorizing' carbon* Gattermann reports that the.aldehyde is easily purified in this manner* Two grams of sodiiim hydrosulf ite, were boiled with an alcohol o solution of fifteen grams of the ''aldehyde. This procedure removed a large amount of the amber colorj leaving the solu tion a clear, light yellow. The use of.hydrosulfite should prevent any oxidation of the aldehyde due to oxygen dissolved ■ ■ in the water, arid may be used iri many cases where one is work ing with the less familiar aldehydes .and has little knowledge of their stability= The purif ied aldehyde’f ormed in very - fine, light yellow needles which melted at 181°C as.reported by Gattermann. . ' v: : I . '' - :• Preparation of 2-Hydroxy°l-naphthaldehyde (B-Maphthol Alde hyde ) . . '" v '■> ■ " '/ ; ^, : General Directions;;B were followed. Again a very small ratio of zinc: •cyanide/to phenol was used:* In this case., equal weights of each were; taken. The bright yellow imlde.hydrochloride was hydro!!zed by boiling / for five minutes in 100 cc of water. A'1 red oil formed in . / ' the hot . solutiori and was removed. White crystals separated - from the filtrate:arid were found to melt at 82°C. ^ The. red oil solidified iri brown crystals which could be> purified '. by dissolving,. them in a hot alcohdl-water solution and allow ing it to cool. In each recrystallization about one third . of the/ impure aldehyde came, out of ", solution as white crystals 25 ■while. the Remaining two ^thirds precipitated again in the . -dark formo The yield was ten-grams3 57% of the theoreti cal yield® . ' ■' -> In thesa last two reac tions the amount of zinc cyanide ■ ■■used was reduced considerably from that used b y .Gattermann«, V-The .product’s were both good and the yields were high* . Gat termann reports a yield of 85^, but that is calculated on the uhpurified aldehyde * A 57%' yield of pure product was . obtained, from an 81% yield of impure .aldehyde. Preparation of 2 S4,6-Trihydroxybenzaldehyde (Phioroglucino1 : Aldehydeh/- .- ' ■■■.■.. h. :: 'i'; -y.yi ■ '' General Dir ectlons B were followed*' i t i n , The imide hydrochloride was a heavy, orange colored solid* . - Mien added to 250 Co of water for the hydrolysis ^ it immediately dissolved^; forming a. dark orange solution* When this - solution, was.boiled for 10,minutes, there formed a hea^ry red precipitate which melted between 145° and 155. G. Molken and H i e r e n s t e i n ^ r e p o r t the aldehyde as having no definite melting point* . The aldehyde.:was never complete ly purified and any .results obtained with the Schiff reagent will have to be considered as general interest information until a better product can be prepared and tested* . Pr epara tion of 2,5-Dihydroxybenzaldehyde (Gent is ald.ehyde). ; ’ '1 . ' General Directions B. were f ollowed* ; : .. 26 The gentlsaldehyde had previously been prepared by pro cedure To However#."the yield's: in.' this preparation were very poor# although a good product was obtained. When- the aide- ; ' - ':r': V . ■ v ..1 ( 2 1 ) : ; hyde•’*&&•.prepared by the Reimer-Tieman reaction and ; ;; modifications, thereof j,; the yields were even poorer.. : Bince: this aldehyde seems ■ to ■ be one of the more diffi- . cult to prepare# it; seemed of interest to cbmpare the fe-'-:.: suits of the "synthesis of gentisalde-hyde by the Gattermann :procedure wlth the other methods used®; • . ■ ■ ■ - The reaction was; carried out three times. using the same;. general .procedures used with the o ther aldehydes. A milky ; oil formed slowly and solidified as usual. However#.the color noticed in the other intermediates was absent. ; The . ■ precipitate; was hydrplized, with 500 cc of boiling water. . ■ iihen- this solution was cooled to zero degrees centigrade# : a heavy brown precipitate settled out. This -proved to be unreacted hydroquihone. ' - : . V;; Therefore# the Gattermann Synthesis using General if .' Directions B.seems unfit for the preparation of this aide- Preparation of 2# 5-Dihydroxybeuzaldehyde (Catechol Aldehyde). ■ ; iGeneral Dlrecflons B were followed. . ' . . i'Several: attempts were tmde;to prepare ah aldehyde from: catechol.by the Gattermann synthesis. A purple intermediate f ormed which never : completely ,solidif ied. . This . heavy oil 27 was hydrollzed: in boi ling water f omlhg ' a purple solution, , ' A precipitate of fine gray needles "formed in the solution - : during slow evaporation^ but they proved to"be unreacted .h.ateebbl.V V.;- ; , " y'ly t ■: . : - i.h : Catechol is d-dihydroxybenzene and should have yielded -835-dlhydroxybehzaldehyde if the reaction had been complete, Pauly.and von Buttlab list this aldehyde as giving no definite , color with Schiff reagent o; ' However$, in a short discussion . ' , they say- it reacts somewhat less strongly.than gentisalde hyde » which gives a good test. This is a confusing point® ■ It is unfortunate that time did hot allow the preparation of this aldehyde" by ahothen method, - " 'y ' PRBPiM lcm OP REAGmf. v - ;'-^Itlxoiigh. of. approximately the- same qualitative composi tion-^ Schiff test reagents employed, by different authors are found to vary considerably from a quantitative standpoint« In many papers9 no mention of the test reagent composition is made at all„ This lack of agreement among'different in vestigators may well be one of the important factors respon- '.sibleifor: the contradictory reports of Schiff test results fouhdtin the literatureo- .Preliminary work.in this laboratory had Investigated a wide range of reagent compositions with a view to deter mining the most sensitive«>: This showed that the composition ' ■ ' 'i-:: ’ V : - ■ (Ig,) - ' . . reoommehded by; Eulliken: - was far. more sensitive than most and was excelled by none of'the others triedo It was-also noted that different .preparations of fuchsin resulted in reagents of different sensitivities>. .'The ;reagent used: in the ..present:.Investigation was pre pared from Basic Fuchsin (Coleman and Bell) according to the directions of Mulllken: Add Of 2 grams of fuchsin to 10 ml of freshly saturated SOg solution. Allow to stand until .color less (or 3 hours) and dilute to 200 ml. : . ••d.i.: :.Boll and; cool all distilled water before use in ' f f 'order to remove; dissolved oxygen. Saturate the boiled .- mater with SOg at ice temperatures to insure rapid attainment of .saturation. : Avoid-, loss of 80g f^om.'the sat'urated sol'atiori by making u p the'initial solution in a small vessel ' Which eah be stoppehed tightly while standing<> ; / T M S C E M )fE S $ PROCEDURE ■ : ■ The writer feels certain; that the procedure; used in ; testing the compounds is of the utmost;: importance -when "work- • ' ingv: withthe’;"Echiff color reaction* Most, of the articles -: • listing anomalies in^the test'fail to.Indicate the procedure. . used in he sting and preparing - the reagent» ; Shoe smith s,: Soss en, • (20'l ■ . ■and >letheringtonv _ ' have shown that various results can be ■> obtained using 'different reagent compositionsbut little is ' • . said. in. any; article about.-the procedure used ;in .testing the , v; aldehydes = : .1 . : = "" : . i.,: ' / ' i:.;; O'- ^ ( i d y -: :' '' t ; ; •: - i n t ; - -h : i C t - hi son 1 ; / ; in. .trying. .t o. prove h: complete lack:' of reliabil ity in the tests' lists .numerous; examples of' •non-aldehyde- type - -'compounds which do give ' a test» It -has been known that the ' alkalis f orm a color with the ' reagent* Theref ore,- any com- i pounds, as the ; saits of weak’acids,; which will form basic, i : v;; solutlohs: will; give -a - positive test* ' Peulgen^^l and his col laborators have ihdlcated precisely the precautions to take in order to avoid -this source of"error in aldehyde;researchi The color'obtained in the trne reaction is a different shade .' thanothat foimd/in the- pseudo .reaction* . ' . ; ; This pseudo.; reaction. Is merely the reyers.Ion of the color- lesa dye-1o ,the quinoid - structure due to the Toss Of sulfur dioxide 0; ;The:vpresent - writer will agree with Li son. that even . ; the trained observer may have considerable difficulty in recognizing: tlie' psetido reaction^: but realizing the diff icul ties arising in "basic solutions, the investigator can beware of such conditions and avoid them« ■ Lison also lists acetone and other low molecular weight ketones as giving a"test. Acetone must be recognized as- a •d:efinite limitation, in the reliability of the. re a c t i oh» .;; If In testing a- however, two or three drops only, of the unknown'., are.used in three ml of gohiff reagent, no test is obtained • with these, ketoness If two or three ml are tested, as the 1 present writer feels hi son may have done s_ then a positive test invar i ably '/results „ ■: -The same results are obtained withl the . ke toe s t ers s as e thy la c e t o ace t at e will give a test if two or".. three ml are used instead of several drops» " Edsdn ; seems;, to :pay littleiattehtioh to the time factor . in his.- e-xperimental work® Many compounds will undoubtedly give a color if.allowed to stahd for an hour® Lison says , oleic acid will form a color" in 30 to 45 minutes® The reagent itself may give a colory if allowed to stand this -v/: : ; Since positive results can be obtained with the non aldehydes under the above conditions« the test procedure must be made specific® .1 : ■ . / • 'i': - " 1® . Two- or three drops; or 100 mg, of the aldehyde are added to three ml of the Schiff reagent, After gentle mixingp the ’.test tube is allowed to stand two minutes® The .appearance of a color in two minutes or,less constitutes : 52 : ' ; - a positive, test» ‘ / ''y;-'.-/: y- ,: ; y -if ;. Wa aldehyde" ;Is quite insoluble in the reagents a - . concentrated" ethyl alcohol solution of the aldehyde, ; ' • , . ; y . should-"be made and three drops, of this 'solutlon"- ■ i';’ t ; ;; V tested^' " In this case a blank should be run on the. ’ i ethyl alcohol, y " " ' Jl^ yy ; y ' yVyo';■.,i: V .yy;;" y ■' 3<, If the test fails in, the first two casess the reagent : • . and aldehyde should'be shaken vigorouslyfor two mih^ • y- . uteso In this case a blank consisting of -three ml of . ' y the ‘reagent; should be shaken in the same way. If these procedures are followed5, the test for alde hyde s becomes quite specific» Although the.present writer has not thoroughly, investigated all. the .anomalies listed by y y: y- hi s ohihe'yfh ela c er t ain most of them " would bey E liminated by : such a procedureo ;:y ■ . yi- • ;y In testing the aldehydes many experimenters have listed y ■■ y 'Speeds of y color: f ormation and their Interpretations of cdlor intensl tyi ySuch cdmpar Isons . of colbr . c annot be .made obvious, o to a reader : and often tend only to confuse him* Each ex- . ■ "yperimenter must thoroughly familiarize himself with the color - reaction and then determine If the test is positive"or nega tive for the less familiar aldehydes I . -. y ■ - y .. They present writer will therefore list the test as positive nr’'negative and: compare-the, intensity of color only .: - as faint $,. weak, strongs and ..very y strong 0 Any aldehydes y.. 1 35 which for# # precipitate with the reagent will not automatic- • ally he rejected as giving a negative teste Ifa with the formation of a/precipltate, a color reaction also occurs, and . if the color formed meets, the conditions set down as con stituting a - positive teat, then the aldehyde will be listed as giving a positive tea to ' *■: "I rf: f.-h , . • : . > ,1 ISinoe the difficulties arising in the test occur with the aromatic aldehydes* very few-of the aliphatic aldehydes ■ • have been testsdo 7 ■ £ small group ;was tested- to; obtain an idea of the intensity .of the test and speed of the color ;: :f ormatlonicompared to those that react normally , :; i n ; \ \ v,; • test . results - .,y.; $he following were obtained when testing the .h. : ■ aldehydes with the sensitive reagent and usIng ’the dlreo™ ' ; ■ tlonSygiveh ahove'o;. ; 'y'.<-;: . -''V; >-1-.". ■" V - .■ y ; - y'yy^y;:" : ;■:> y; ■ A ^isA T.ia'ale & ydes 1 :- ■ . y.- y .; y -" '1 1 y Formaldehyde Very strong color immediately „ y E ey ■ Crotonaldehyde ' ' Very strong color Immediately0. SI 2 -E thy Ihu try aldehyde - Faint test (easily missed )i i / : ' .if ; :' ' /I . ' In alcohol solution ^.' strong . '; ■ ’ ■ ■ ' color in 5 seconds, 1'. y . : 4, - Furfural ■ - y ; y ^ 1 \ 1 Very' strong colorin 5' seconds, 5, ■ Isobutyraldehyde. ' Very strong color in 2 seconds, ' 6., Paraformaldehyde Very,;strong color immediately, i yyy-y ; ...y y ; y ' y .. : y .when first depolymerized, 7.. Propionaldehyde. - y , Very strong color Immediately. So- 2-EthylhexaIdehyde Weak color immediatelys strong ■ y ■ ':yyyy;y:y y:,yy.y m. : y :;- : ..:y:;y:;-yy,:y.y 9, . n-Heptaldehyde y. y • Very strong color in 5 seconds^ 10« ' h-Btttyraldehydey-; •: y " : : . Faint color Immediately$ very ; y . ■ ■ y . i ': y :y 1 : , ' strong color in 5 seconds. ’ ■ 11 o • a-Ethyl-b-propylacrolein .. ysffeak . color in 2, seconds $ very y ■ (SrEthyl-hexenal) ; strong color in IB seconds . ; (y y I ' ■' AROMATIC ALDEHYDES ' 1^ - Benzaldehyde -I ‘ : ; ■ _ Very strong color immediately, 35 : ■ " AROMATIC m E H T O E S . (C.ontinu©d)^^^^;A^ : ; 2, ■ Glnnam.aldehyde ’ Yellow ;color ■ .l^ollowed 5Y pase- : ' / : 1, "I :":: 7 ' cIp 11 ate whltib darkens: giving .. . ■ : a red purple in :one minute 'aiad: ' ; r ;; — • . - a purple in 1^' minutes = Very; ; ■ . 'f*: • : * : strong. color'o (positive test) V; ^3. - EYdrbcinnamaldehYde Very s trong color in 3 seconds -, ; ' /.4^ ip^Isopropylpeitaldehyde Weak color in 5 . seconds, / strong" . (p-Guminic aldehyde ) ■■ color in 15 seeonds. - - >1 5,. a-n.'-AniyIcInnamalde.hyde .. Very weak test. In alcohol sol™ • " : - yution; - faint color 25 seconds; . ; : , 1 , 'I .good boldr 35 seconds| strong . . ' / •; : .cdlor 1 minute =, ; ■ 'g 6 . - 'o^Anisaldehyde . Vety strong color in 5 seconds!g / Vo : p-Anisaldehyde - y : :Slow-forming: colors very, strong"- . ' . g.' - . y - -coior' in .30 secondso ; : ;So 'o-Bthoxybenzaldehy.de : Very strong- color immediately» . y 9.0 ■ p-Methoxybenzaldehyde yvery strong color in 4 seconds« v 10o m-Nitrobenzaldehyde : Very strong color in 5 seconds0 llo o-OhlorobehZaldehyde ■ Very strong color in - 5 seconds» 1 2 o .. Piperonal : Paint color in -30- seconds'; ; y . ;- - ■ y , , g -weak color in 45 seconds; strong y'I;"y g- .. ' ; " y g: ' color in; 1.minutb 15 seconds, : ' y y.-'y y: - y ; g- : (positlye ,test).. : -'. y: ■v } y 13» yySallcylaldeh^'de'y" - : Very s trong color ih 5 seconds» y(b-Sydroxybenzaldehydey o ypyg , ; .g l -, 1 '- ■: 1; : -- y! ' 14o p-Hydroxybenzaldehyde. Very strong:color in 5 seconds» 15, mvHydroxybenZaldehyde . Very strong color in 5 seconds. ' . 16o' 2“Hydroxy- 5-bromobenzal•= No test with solid, '. In alcohol. . . g, g ./.dehyde g : ' g- solution forms white solution g.:: g - .r ; ■ - : cbloring in 5 seconds,' Strohg y ;-v- 'y:;.:' y-.yy y;..; ' , yy test, y - gy y ,yi ..--v y - ,;.V; 17, g. SgSydroxy-S-chlorpbenz-y .Slowhforming color with solid, " , aldehyde o , : : : - ' In a 1 cohol solutIon forms white V: g'-' .gy y ' ■;1 g : ; , - ; precipitate which changes in 3 'yg- - .y"y i ' gv:-.' * - v seconds to strong purple, .- . ' 36 :iffiOMATIO ALDEHmES:: (Continued) 18. - Sj, 3-Dimethoxybenzaldeliyde Weak .color in ,10 seconds | ■- very strong in;15 seconds. - 19 s 2 ,,4-Dime thoxybenzaldehyde . Yellow color, slowly f orming: precipitate. In alcohol _: : solution - yellow precipi- \tate immediately. ' (no test) 20 o C 3-s 4 -Di e thoxyb e nz aid ehyde Weak color in 20 seconds;; . ■strong. color in. 30 seconds. ’ .: 21. 2 '-Hydroxy - 3 -mo thoxyb e.ng- Very strong oolpr'in 3 sec- . • ' aldehyde':■ : Ond's. : V . .4' ' ’ - ■ :4.:- v : 22. . 3-rEthoxy-4-hydroxybenz- v. . paint color 25 seconds| . v (v . ' ; • ' i aldehyde - ; n . ; i \ weak color 1 minute • (easily recognized) .y."- 1 ■ ■ 23.; ■ yahiiiin: i ; >: ' Chy . Faint .color 30 seconds;• strong (S ”Me t bxy ^1-hy dr oxyh eh z al - color 45 seconds. dahyde) ' :; \ 24. : 3?4-Dimethbxyhenzaldehyde Very strong color in 15 sec - - ■ _ (¥• e r a t raldehy d®) . onds. - v y c y ■ . ■ '1 ';' ■ _ 25.. 3“Ethoxy--4=hydroxybenx-f Weak color in 10 secondsph - : v i aldehyde ^ ‘ ■ very:strpng in 20 seconds. 26." Proto'cateohualdehyde ' Faint color 25 seconds;. /./l-d ' :(3y4-dihydroxybenz aldehyde )'strong. in 85 'seoohds. ; ■: : • 27 . 2 j 5 ™D ihydr oxybenz aIdehyde - Faint color 10 seconds; ",' (v (G-entisaldehyde) strong in- 25 seconds. - ' - . v: ; 28. 2g 4-Dihydroxyben.zaldehyde .Solution turned yellow; formed yellow precipitate; • in 2 minutes, Ifno test) 29. 2$ 3,4=Trihydroxybenz- : Solid forms yellow solutions aldehyde ■ . ' In alcohol" solution - yellow . (Fyrogallol: aldehyde) n solution. (no test) ? ;• 30. 2=Hydrox:y-1 -naphthalde- ■ In alcohol solution - yellow hyde - - . ; ;:': v . colorj slight precipitate ■ (b=Naphthol aldehyde) (no test) 'y: y - 31. 4-Hydroxy-2-naphtha Ide- In alcohol .solution - light ' hyde ■ yellow color deepening to : •; . ;:':>v (a-Haphthol aldehyde) trange trown. : no - test); 57 :AROMATIC ALDEHYDES (Continued)' 32 o p-DimethylahilndSenz- /- Br ight yelle* .color imitie- : :: aldehyde diately, slowly forming a Rrecipitate. (no test.).:. 55.. ; Dhclnol aldehyde Solid (no test)| in alcohpl . solution, a- cream, colored ,. precipitate -d.eepening to - ,V ; 'yellpw-green.'(no test) ■54, .2,4,6- Solid (no test). • In alcohol aldehyde s-olut.ion (no test). . /I ■ (PhlprOgl-uclnol - Aldehyde) HOR-ALDEHYDE COMPOUNDS 1...... Isoeugeno 1 No test 3 :drOps. .and; 5 ml an orange co lor is'/; obtained in 1 minute which ' darkens to a, posit lie color- test in l|r minutes, strong . . in ' 2,\minutes., ': /, : - /' , '. 2. Ethyl /alcohol'. ,N0: test 3 .drops| strong test in 3 .seconds with 5 ml. 3. .Methyl,, alcohol No/test 3 dropsj strong test immediately with 5 ml. 4. n-Butyl alcohol No test 3 drops|:strong test 3 ml. . 5... Amyl alcohol No test 5 drops; weak test in 10 seconds with 5 ml. 6 . Isopropyl alcohol No test 5 dropsstrong' ■test /i/ 't' i-v;// 7. Tertiary butyl aleohol No. test 5 drops; weak test" 5 ml. ■ ' i . . '. ' 'r . . \ 1 / 8. Isoamyl alcohol / No test 3 drops; strong test S'mioi ' ■ -: : : i.2; \.- ' - . -'. I \ / - 38 ; : . 9o . dycibprop5"l; metHyl: '6'etone Ho test 3 dropsj strong ■ , . test' In. 2 seconds with 2 . ml, .. ' ■ ; 10, Methyl ethyl ketone. No test 3 drops; strong test ltt.-2. sjeeohds with 3. ■' mio i:-' ; 11, \ jioetone - . x, .; • No test 3 dropsy strong test In 3 secondsrwith 3:-;/'i' ^ ml, ' .-' 12, ■ Ethylacetoacetate No test 3 dropsj weak test in 1 minute with -2 or 3 ml. . pisciJssiQr ^ The compounds tested have been listed generally in order of their increasing domglexityo All of the aliphatic alde hydes tested gave a strong' positive test with the sensitive v reagent <. . The color is not the red color of the or iginal dye * To the trained observer this should be,of some importance in testing. an unknbw'n compound for aldehydic properties o ; . ■ • ' The present -writer feels that some experimenters have found it difficult to obtain a test with certain aldehydes ? . -Some, of them" aliphatic, due to their Insolubility in the ' h reagent« This, may have .led to " the recording of a poor reac=. • tion with a compound which will, actually give a very strong .test .when in solutiono This is especially noticeable with the aromatic aldehydesf sihce many of these compounds of ; i large molecular weight are insoluble in the reagent. The re act ion of 2~b.ydroxy~5~brorfl.obenzaldeh.yde is noteworthy« No .'teht* :i8 'bhtaihed/ at.; ali: ilth -1he .aolid aldehyde» - An extreme^ ly Strong test is obtained in ohly five seconds.when three .. drops of an alcohol solution are tested= Some;of. the ali= cphatic aldehydes of large molecular weight may behave simi- larly» ' Of those tested S-ethyIbutyraldehyde ;did not givev a .. good:test until dissolved in alcohol,, in t Pauly and von Buttlar^are correct in;their statement "that the. ;25:A^dihydroxybehsaldehyde;'does not give a testo • ’A ; 40 yellow preolpitate is .formed and under various conditions ho improvement was made in the test of this aldehyde= The yellow precipitate forms rapidly and becomes quite heavy* Wo red color develops at alio. The 5$4-dihydroxybenzalde- hydes protocatechualde.hydes is also listed as; giving no. color- ‘ at all® .This was found to he an error«y This aldehyde does - give a good test although;it forms more slowly and is weaker - than other So,, It is's. however ? easily, recognized and should never be missed. The o-protocatechualdehydes 2$3-dihydroxy~ benzaldehydes Is said to give as,weak;a test as the proto- ■ ; catechualdehyde. Using the sensitive reagenty a positive : test is probable. Unfortunately$,. this could not be verified as the aldehyde was not. available. The' 4-hydroxybenzaldehyde which is said to give:a barely distinguishable test in two .'minutes was found: to give a very strong test in only five seconds. Gentisaldehydej, : 2S5-dihydroxybenzaldehyde, as; re- ported by Pauly does give a strong test. .This ' is noteworthy - as the dihydrbxybenzaidehydes generally^seem to give weaker tests. -■ - y.-/'. ■ ' Schmidtnoticed several peculiarities in the reac tion of cuminaldehyde and cinnamaldehyde. The present, writer verifies Schmidt is report that cinnamaldehyde- formed a yellow color at first: which soon (one minute) changed/to a red purple color. This-meets the requirements previously stated and the test was considered positive. Schmidt did not . report the ' - ■ ; length Of time it took for the - test to form a .color. ' However, he undoubtedly got. a strong color and a .good test» With cum- Ihaldehyde Schmidt reported a color after a little shaking which is diff icult - to ..interpret«; The aldehyde^ was found to give a color in fifteen seconds-using the sensitive reagent. .Bela von Bitto' ° reported difficulties with cinnam- aldehyde and cuminaldehyde as did .Schmidt. Onminaldehyde, he said) gave. a very weak) very slow appearing color» He also reported difficulties with vanillih and anisaldehyde =. " . All of -these were found to give good results with, the sensi». tive .reagent o . " - . '’i;- :-o i i' i . , - horenz(^ ) reported piperbnal as givingra yellow dye- stuff which turned red» Piperohal was^ found to react more s lowly •than most aldehydes tut no, yellow'; color, was: observe do r; Shoe smith) Sossens and Hetherington^ ^ have listed: a ■ large number of aldehydes as giving anomalous results with' the :Schlff testo: Their results have been reviewed previous^' ly»- (see p 11) The results of these authors are extremely " ■misleadingo. In the table of aldehydes they list as giving .precipitates5 all of those tested by the present.investiga- • tors 'with; few exceptions,. gave a positi.ve test with the. . sensitive, .reagentv • ' : -: z: t --".'t' ;■ '' ; , V: Salicylaldehyde, p-hydroxybenzaldehyde, vanillin)rand ; V- cinnamaldehyde')- all. of'which were listed as giving- poor re sults ) were found to give, a good . testo; The. 2? 4-dihydroxy- ' benzaldehyde listed as giving yellow precipitates is definitely an aldehyde which does not giye a test. The 2-hy- droxy-l^naphthaldehyde gave a negative test.; . Only a yellow color and a slight precipitate formed., It is very likely ■ that the 1-hydroxy--2 -naphthaldehyde does give a negative test as listed by Shpesmlth. .• Thev-present,' writer has tested .4-hy- drOxy-l-naphthaldehyde and got a negative test with this V compound. ' Although no results of tests on the- various other- vhydroxynaphthaldehydes were found in’.the literaturej, the present author feels certain they would give a negative test, since the two aldehydes of this series which were tested did Vhot - give: A i test and Shoe smith reports another of these as giving a yellow precipitate instead o f t h e ’.characteristic . ’ . purple . color O • . i ; : v" Also: listed by - Shoe smith as giving anomalous results ' were three of:the" hydroxy-methylbenzaldehydes. ^ . V ’ - . 2 -hydr oxy =• 5 -me thy lb en z aldehyde . ; • g^hydroky~4"Methylbenzaidehyde . ; . ’ - 2=-hydroxy-5"methylbenzaldehyde . The hydroxy-methylbenzaldehydes have not been tested by the : present : wrl ter» . .irowever, the . subs titution of ' one - me thyl ' group fpr a hydrogen in the benzene ring.should have little or no effect on the activity of the aldehyde. Since the • three monohydroxybenzaldeiiydes were found to give strong tests,. ;It seems probable that these me thy lb en z aldehyde s give a good test. Shoesmlth, Sossen and Hethertrigton have used a re agent; of such composition that they got -anomalous results ” 45 witli, eompoxmds.v(suieh; as .salicylaMehjde and piper-onal) which actually give very, s trong teats with the , sensitive reagent Several- aldehydes of similar structure, were testedf all of ^ . which gave positive :test8^ - : ':; : ;' .; /: f yf' 2-hydro^-5-chloit>henz^ldehyde f;; - y - ■- 1 - .: - . i ■' ; 2-hydroxy-f5'?:bromo'benzalxiehyde-. v:. _ : ' . - ' 2-hydroxy-5-methoxybenSaldehyde - : : S-hydroxybenzaldehyde ' From these, results it is seen that the o-hydroxy&romatic aldehydes do not generally give an anomalous test as concluded ' by Shoe smith Sossens and Hetherington. The 2 $, 4-dime thoxy- benzaldehyde listed as..neutral- tdward the reagent was found to give a yellow precipitate with,the sensitive reagents , Li son lists d ime thy 1 ami note n z a 1 d ehy de and piperonal as giving no: color at •' all while' vanillin reacts weakly . The dimethylaminobenzaldehyde did - not give a positive test, but - formed''a yellow' Color immediately which slowly changed to a - .*- precipitate^.Eowever, the other two aldehydes did give ' a' good testo • . -f-yV 1 : - :'. y ;■ ■ ;:: - . . If three ml of ’acetone are tested, a. positive result is obtained. When two or three drops are tested the -results are negative.■ -The same holds for the following compounds which - - Li son lists as giving a Schiff testr Me thy1 alcohol, e thy1,al- coho1 , prdpyl aleoho1 , dlacetyl, ethylacetoacefate, methyl ethyl. ke t one f • eye lopropyi methyl kef one,; isoamyl alcohol, tertiary butyl alcohol, Isopfopylalcohoi, amyl alcohol, n-butyl alcohol. 44 : . Isoeugenol was said by. Llson to give a stronger test than- vanillin,, the ^aldehyde/derived from it by oxidation^ This was found to be incorrect®. , Again, .if two or three ml ;. of Isoeugenol are tested wlth :the .reagent, a . red color - i-1 1 . develops rapidly<. With two or three drops no color develops at all o Vanillin, on the other hahds. gives a strong test» SUMBIARX OF RESULTS' The following aldehydes which have been listed by pre- : vipus ahthors as giving some type of ;anomalous result; in the Schiff test were found to give an easily.recognized test using' Mtilllken1 s reagent and the procedure set forth in the ■ early part of this paper. ' (see pe 34} .• ,;. lo " cinnamaldehyde -1 ' -- ' - ; . ■ 2 6 .: p-cuminlc aldehyde..; . v. ; - ' ;L:; ■ ' r:-: ;■ piperonal : - . .. , : ' ‘ l , '1 ' * ; ' ; vanillin; 1 - - " Vt . 5» protocatechualdehyde : ; - L . ,/ . :; 6 » . sallcyialdehyde '/ " :" ■ . : : V o ■: p^hydrokybenz aldehyde r ; ■ . - : : • 8« . andsaliiehyde , % - ; % . : : ,; . .1- ; .. . A. large number p'f aldehydes of'•structure similar to those.reported as giving anomalous results» mainly the dihy- droxys dimethoxy$ ■ diethoxy,, and mixed hydroxy ether ’ benzal-' : . dehydes g have be eh tested. With few' exceptions a readily recognizable, color developed within' two minutes = . Some of the anomalies rep'orted by various authors were verified. The following aldehydes Failed to give a recog nizable test. ' : . ' • .'nv ;W' v':-v ' • - ; i: ' • . '"1 ;1 . ' 2s4“dihydroxybenzaldehyd@ . ; r' .l :. 2. 2$4-dlmethoxybenzaldehyde, . , 46 ; v; ■ Si ; jbm ...■ ', ■■'■>;■■■;■;■ r :; V -4 , a :8-33ydro^-i”naplii3j$aldeIiyde v. : . ; ” V '•' . , p-dirriethylaminobenzaldehyde ' .• - : ■ : The f ollowing aldehydes■3i; no; :nepondshaving been fonndth of previous testing, were tested’ and found to give negative . results. ■ •. - ' : : . ' ■ V ■ • • ; lo orcinol aldehyde - . • ; . ■ . ■ . " 2 «, phlorogluolnol aldehyde / . .. v • ' 3 o’ ■ 4-hydroxy-2-naphthaldehyde' . . '% _=¥ ;. A group df non-aldehyde c omp o unds rep or ted as gi ving a ’ positive test with the Schiff reagent was tested and found : to give negative results. . . GOHGLUSIOHS 1» The monohydroxybenzaidehydes do not give anomalous resultso All give, a strong test Including p-liydroxybenzalde- hyde which Is reported In the literature as giving a very poor test »• y-V-l;::'' rt';.u't.. t \ So Most- monohydroxybenzaldehydes further substituted by other groups'■give a positive- test. / . The various dihydroxybenzaldehydes react less 'read ily than the monohydroxybenzaldehydes» but only 2 S4-dihydroxy- behzaldehyde gives a negative test. . 4. : The methoxy group seems to have' little effect on the acfiyity of the ’ aldehyde exceptvihen' substituted in the; 4- ;pb.s it Ion o Here it leads to the formation of ho purple color <> :'5.o. The hydroxy naphthaldehydes, the . trihydroxybenzalde hyde s® and the larger molecular weight poly-substituted ben- zaldehydes in general can be expected to give no test at all or? at bestj a very poor one» 5. The Schiff test is quite specific for the aldehyde group * - All:non-aldehydes tested which were reported by Lison as giving a positive test were found to give negative results when the test was properly appliedo - . 1 .. . . ' 7. Aldehydes which give ho test at all> or at best a very poor one* dp© to their extreme insolubility ih the reagent were found to■ give a strong test if the procedure set f orth - this. :author .was. useho - -, ? x : ‘ . x .; ' / . . 8 0 Shoe smithy Sdas.eh and Sethering toti ara. in error in ooncluding that.' d”hydro:x^ardfflatx.c aMehydes. -generally give :ah, ahbmaloua testt^ x.:f ' ■ ; x " ' ' 9, The Schif f test is a reliable^, simple .test-for aldehydes if used ■ahd 'interpreted- correctly = .; Only a. few of the. 'more; complex aromatic aldehydes fail to give, a test. Most -of . theses howevergive a yellow to orange colored pre ' clpltate while the non^.aldehydes,; show no - sign of a reaction taking.place at all.- The yellow, precipitate is not a posi tive test, hut is an - itidication:that, the: compound may be an aldehyde and should be .checked by, some. other method of aide hyde :identiflcatibn.ghi .- i-kh /'k';:- BIBLIOGRAPHY. ;I 'lo Adams and Levine, J„ Am-o' -C&em« Boco:? 45s 2373 (1923). ; / ; . j S. Adams and Montgomery.s Jo Am, Chem* Soc», 46; 1518 (1924)«, : ; 3o . Bellatein, Handbnch der.Organ!schen Chemie, Edo 4, VIII," " 1 y Berlin, Julius Springer, 1910, p 244» • ■ v J I: ’ . 4= Bucherer, Lehfbuch der Farbenohemle, 2.94 (1914) «>. ' -. . J ; Bo Oarb^' Bero, 15, 2543 (1880). ; ' ; . : : ' ■; .6'o.. Burysebnabe 1 and llell:, B e r o 5.8,- .3^ 1905). ; . r 1 ’' : 1-71 Feulgen and Rbssenbeck, Z fur Physiol* Cheml, 155, 203 ; ( a 9 e 4 i - ::.r: 8 o. v Hantsch and Ostwald, - Beri;, '55, 278 (1900) „ :V-; - . ' ; 9o Hodgson and Beard, J, % e m » ; Soco., 150, 2359 '(1927) = ■ / ■ /.' 10.. - Lis on. Bulletin d*Hlstologie,_9s # 6 , 177 (1952) d, 11 o Lorenz, Ber <,, vl4, 785 =(1881 )o 12o Mollcen' and Hierenstein, Jo Am, Chem, Soc», 53, 242 ('1951). .l3o .Mulliken, So P», IdentlLication of Pure Organic Compounds. V : .. ' Edo 1, London, John Wiley and Sons Inc „ s 1904, p 15, ' y. l; :.' l4 o Panly,: Schuble and Lockeman, Ann., 585, 288 (1911). - : ■ 15. Pauly and von Buttlar, Ann.,"585, 230 (1911). . ; ; ; - i - 16. RLodes, Ho- Do, private c ommuni c at ion 0 I. ■ .. ; 17. Schiff, Ann.; 144,' 45. (1870). . : V ; - u' / : \ 18 o Schiff, Gompt-? rend, f 164^ £182-(1886). I''--' d . . ;;':' . V/ ,:.19o Schmidt, Ber. , 14, 1848 (1881)»' - ' ' ' r :. 20o Shoe smith," Sos sen and He ther ingtdn, J. Chem. Soc., 130,. u.;:' . 2221 (1927). , ^ : i; 21. Ti-eman and Muller, B e r 14,. 1986 (1881). • Vogel^' Jl.o I Text-Book of Practical Organic Gheralstrys • . Sew -YofkLongmans G-reen and Co. , 1948; p 1960 .•■• - - 23.0 von Bitto, Z » Anal» Chern.', 36, 369 (1897) . - . :24o Wieland and Scheuing , B a r 64:, - 2527-, (1921) „ ■ : . \ . : \ Bo m ANOMALIES DP TEE SGHIFF A1MJYDS TEST-': ' - ; : ': T Willis Bo Tolley . ■ ' ^ ’ ■ ■ : ABSTRACT ' : ; ' . The Schiff test has been used for years with great sue cess ■as a simple, quick means of identifying aldehydes„ - Since 1881, when the test was first applied to the :iden- :• tifieation of aldehydes, various anomalous results have been cited in the literature« Several articles indicate a com plete lack of reliability in the test. However, these ' ’:: ' articles often contradict each other and give a muddled pic ture as to the reliability of this means of identifying aldehydes,; ;; / ^ It was the aim of this investigator to prepare the most sensitive, 'test reagent ' possible and, using' this reagent, to ; : test a group of aldehydes in the hope of clarifying, some of :■ thev; literature reportsi A large number of the aldehydes . listed in the literature as giving anqmalous •results were col- • 1 ected or purchased» .Others of structure similar to those : ;listed as giving anomalous results were collectedo, Anotherv • group of aldehydes which was not available was .prepared0 This last .group; inc'ldded:h-©v:eral-^hich‘:'.were listed in the liter ature and the rest were, untested aldehydes of a more complex structure which the author, felt would give a poor teste, h;: . .; Shen:.testIng the aldehydes $. tt was found necessary to establish "a specific test procedures which many previous writers had hot. done l;- v li:;,1'. 7: :; v - ' . The results of the experimentation revealed:- ' ' ' ■ lo All the monohydroxybenzaldehydes give" a strong test, , . ; : ; ; 2= Most monohydroxybenzaldehydes further substituted by oiher groups' give; a positive: test, , 5, The various dihydroxybenzaldehydes react less - readily than the monohydroxybenzaldehydess but only the 2 $,4-di hydroxybenzaldehyde gives a negative test, 4, The methoxy. group seems, to have little effect on the activity of the aldehyde except when di- substituted in the y 2s4- position. Here it blocks the: formation of a purple color completely, : ' i : ' ■ ■ • 5, The hydroxynaphthaldehydes* the trihydfoxybenZalde-. hydes, and the larger molecular weight polysubst1 tuted benzal- dehydes in general can be expected to give no test at all or, at bests a very poor one, i .. - ; 6> Aldehydes which give no test at all $ or at best -a' ■ - very poor one, due to their extreme- insolubility in the ' : reagent were- found to - give .a strong test i f . the procedure set forth by this author .was, used, ^ : ; - ■ . : 7, Shoesmlth^ Sossen and Hetherington are in error in concluding that o-hydroxyaromatic aldehydes generally give an anomalous: test,. 1' ' . ■ ■ 8c. The test .is D^trpo^l^lveyfor anY of the non-aide hydes if/the procedures set forth by this writer are used