1002

LXV. -lodoso- a72d IoCloxyx- beizxaldeh ydes. By THOMAS STEWART PATTERSON.

THE first, representative of the class of iodoso-compounds prepared was orthoiodosobenzoic acid (Ber. , 1892, 25, 2632), which was ob- tained in an attempt to nitrate orthoiodobenzoic acid. A method of general preparation was soon after discovered, and many other sub- stances of this class investigated, one result of which was to show that, as a rule, ortho-substituted iodoso-compounds may be more easily prepared than the corresponding meta- or para-derivatives. This is the case, for instance, with the iodosobenzoic acids, nitro- iodoaobenzenes, and the iodosobenzenesulphonic acids. It was there- fore to be expected tha t the iodosobenzaldehydes mould exhibit a similar tendency, but, as is shown in the following paper, which gives an account of some work done recently in the laboratory of Heidelberg University, at the suggestion of Professor Victor Meyer, just the reverse is the case; meta- and para-iodoso- and iodoxy- benzaldehydes may be obtained with ease, whilst the preparation of orthoiodosobeDzaldehyde i s attended with considerable difficulty.

Meta-iodobeizzaldehyde.-This was prepared by a method analogous to that used by Erdmann and Schwechter (Annulen, 1890, 260, 59) for the preparation of metachlorobenzaldehydc. Ten grams of meta- nitrobenzaldehyde are reduced by gradually adding i t to a solution of 45 grams of stannous chloride in 60 grams of concentrated hydro- chloric acid ; the action is accompanied by a considerable evolution of heat, and it is advisable to keep the temperature of the mixture below 60’. The mass is then allowed to cool, and the metamido- benzaldehyde present is diazotised by the gradual addition of a solution of sodium nitrite, unkil a drop of the diazo-solution colours a piece of starch-iodide paper blue, the temperature of the liquid being meanwhile kept a t 0”. After a, time, the diazo-solution is transferred to a large flask, a solution of 15 grams of potassium iodide in about

* The choice of this designation for the group 10, is unfortunate. The word ‘( iodoso ” was introduced by the discoverer of these compounds in order to indi- cate the analogy between the nitroso-group, -NO, and the new one, -10 ; and tlie resemblance between nitrogen and iodine was further shown by the discovery of substances containing the group -lo,, corresponding exactly with the nitro-corn- pounds, and ought therefore to be called in English, aa in German, iodo-corn- pounds. It would hare been much better to have adopted the names chlorbenzene, brombenzene, and iodbenzene for the substances C6H,CI, C6H5Br, CGH5T, as the simplest possible, so lhat any termination rendered necessary by future work might be added if required, and thus to avoid the necessity of employiog the term iodoxy ” for the group -IO,.--T. S. P.

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PATTERSON : IODOSO- AND IODOXY-BENZALDEHTDES. 1003

SO grams of water is added, and, in a short time, the mixture is gently heated on the water bath until the evolution of nitrogen ceases. A solution of sulphurous acid is then sdded in order to reduce the separated iodine, and the meta-iodobenzaldehyde, which appears as a heavy oil, is distilled in a current of steam. The aldehyde which solidifies in the receiver and in the condenser, is collected, washed with water, and purified by treatment with a dilute solution of sodium hydroxide a t about 60'. The aldehyde crystal- lises from dilute alcohol in short prisms, and melts at 57". I n a Carius estimation of the iodine

0.2257 gave 0.2285 AgI. I = 54.71. CsH,I*CHO requires 54.74 per cent.

Meta-iodobenzaldehyde Dich1oride.-To prepare this, 1 gram of meta- iodobenzaldehyde was dissolved iu 10 C.C. of chloroform, and chlorine passed through the solution. I n a short time, small, yellow crystals separated ; these were collected, washed with chloroform, and dried on unglazed porcelain in the a i r ; 0.91 of a gram of chloride was obtained. The substauce decomposes slowly on exposure to air. The chlorine was estimated by treating it with dilute acetic acid and potassium iodide, the liberated iodine being titrated with sodium thios ul pli ate.

C1 = 23.57. 0.1908 required 12-7 C.C. of N/10 thiosulphate solution.

The white substance left in the bottle after the titration was meta- iodobenzaldehy de.

Neta-iodosobetrza1dehyde.-We first attempted to prepare this com- pound by t,riturating the dichloride in a mortar with a 10 per cent. solution of sodium hydroxide; this decolorised the dichloride in a few minutes, leaving meta-iodobenzaldehyde, which, af ter recrystal- lisation from dilute alcohol, melted at 56-57'. Other experiments were made with sodium hydroxide solutions of different concentration and with calculated quantities of the same, but without much success. Eicher the dichloride was completely reduced to meta-iodobenzaldehyde (ir the product conlained chlorine.

On acidifying the filtrate in these experiments, a white precipitate of meta-iodobenzoic acid was obtained, melting (unpurified) at 150°, so that pa+ of the aldehyde had been oxidised t o the corresponding acid.

If, however, instead of sodium hydroxide, a solution of sodium carbonate be used, which may be quite concentrated, meta-iodoso- benzaldehyde can easily be obtained. The dichloride is triturated in a mortar with excess of sodium carbonate solution until the bright yellow colour of the former is no lorger visible, and, after a, time, the

C,HJ*CH0,C12 requires 23.43 per cent.

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I O U 4 PhTTERSOS : IODOSO- AND IODOXY-BENZALDEHYDES.

meia-iodosobenzddehyde is collected, and washed first with water and then with alcohol and ether in order to remove any meta-iodobenz- aldehyde which may have been formed. The substance thus prepared has a slight yellowish tinge, is amorphous, and insoluble in alcohol, ether, and benzene, but easily soluble in glacial acetic acid; i t decom- poses a t about l90' and liberates iodine from an aqueous solution of potassium iodide at once, although to effect complete decomposition the addition of acid is necessary.

The active (iodoso) oxygen in this compo~ind was estimated by titration just as the ch lx ine was in the chloride.

0.1879 required 14.73 C.C. N/lO thiosulphate solution = 6-27 per cent. active oxygen.

C6H4(IO)*CH0 requires active oxygen = 6-45 per cent. The white substance left in the bottle after titration melted a t 56",

A Carius estimation of the iodine in the compound gave the follow-

0.2094 gave 0.1972 AgI. I = 50.89. Theory, I = 51.21 per cent.

Metn-iotloso benzaldsh y d e acetate mar be prepared by dissolving meta- iodosobenzaldehyde i n a small quantity of glacial acetic acid, and gradually adding hot water until a slight turbidity is observed, theu filtering into a flat dish, and allowing it to stand in an ex- hausted desiccatoib for about 24 hours. The acetate separates in small, colourlesa prisms, the melting point of which is not very sharp, bu t lies at about 157'. It liberates iodine from potassium iodide at once. A titration of this substance was made in the same manner as for meta-iodosobenzaldehyde,

calculated from the formula C,HJ (OAc),*CHO being 12.46 C.C.

and was meta-iodobenzaldehyde.

i n g result.

0.2180 required 12.47 C.C. "10 thiosulphate solution, the quantity

The residue after titration was meta-ioclobenzaldehyde. Meta-iodox?lben,znldehyde.-This is obtained by boiling meta-iodoso-

benzaldehyde with water until all, or nearly all, the solid has passed into solution. I n this reaction one half OC the iodoso-aldehyde is oxidised a t the expense of the other, thus

The meta-iodobenzaldehyde formed passes off almost entirely wittl the steam, but if any remains, steam may be passed through the solution to effect its removal, the meta-iodoxybenzaldehyde remaining in the soiution in the flask. The hot solution after filtration is concentrated unt i l small white crystals begin to form, allowed to cool, and

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PATTERSON : IODOSO- AXD IODOSY-BEXZALDEBIDES. I O 05

the small flakes of iodoxy-aldehyde which are deposited are collected and washed with ether and alcohol, in neither of which it is soluble. This substance merely tinges an aqueous solution of potassium iodide yellow, but liberates the iodine quantitatively in presence of acid ; the active oxygen was, therefore estimated in the same manner as in the case of the iodoso-aldehyde.

0.0556 required 8.41 C.C. NjlO thiosulphate solution = 12.10 per cent. active oxygen.

C,H,( IO,)*CHO requires 12.13 per cent. active oxygen.

The residue left after titration was meta-iodobenzaldehyde. Para-iodoben"a2dehyde was made by a method exactly analogous to

that nsed for the preparation of the metn-compound. Recrystallised frGm dilute alcohol i t forms colourless needles, and melts at 77-78', somewhat higher than stated by Jackson and White, namely, 73" (Beilstein).

kara-iodobenzicldehyde dichloride mny be obtained by dissolving the aldehyde in dry chloroform, and passing chlorine through the solu- tion; i t is precipitated in small yellow crystals, which are washed with cliloroform and dried in the air. A titration of this sub- stance, according to the method previously used gave the following result.

C1= 23.31. 0.4830 required 31.72 C.C. X/iO thiosulphate solution.

The residue from the titration was para-iodobenzaldehyde. Pa ru-iodoso benza Ide hyde was prepared by t ri t urnt ing the dichloride

in a, mortar with a concentrated solution of sodium carbonate. The mixture was allowed to stand for some time (about half an hour) after the yellow colour of the chloride had disappeared, when the iodoso- aldehyde was collected, washed with water, shaken up with alzohol mid ether, collected again, and dried. It is a pale yellow substance, which reacts strongly with potassium iodide, and decomposes a t about 115' when heated i n a melting-point tulle. I n a titrimetric aiialjsiv

0.1276 required 10.21 C.C. N/10 thiosulphate solution = 6.49 per cent. active oxygen.

C,H,(IO)*CHO requires 6.45 per ccnt. active oxygen. It is very soluble in glacial acetic acid, but we were unable to obtain a well-crystallised axhate from it.

Para-iodox ybenznldehyde may be prepared from para-iodosobenz- aldehyde, in the same way tha t mcts-iodoxybenznldehyde is obtained from meta-iodosobenzaidehyde. It cryst,allises €rom hot water in white flakes, and decomposes a t 216".

C,H,(ICI,)*CHO requires C1 = 23.43 per cent.

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1006 PATTERSON : IODOSO- AND IODOXY-BEKZALDEETDES.

0.1380 required 20.92 C.C. N/lO thiosulphate solution = 12-12 per cent.. active oxygen.

Theory requires 12.12 per cent. active oxygen.

Ortho-iocZobenza1dehyde.-For the preparation of this compound, ortho-aniidobenzaldehyde, was first made according to Friedlander's method (Rer., 1884, 17, 456). 50 grams of crystallised ferrous sulphate are dissolved in 120 C.C. of cold water, and to this solution are added 3 grams of orthonitrobenzaldehyde, and 2'7 grams of ammonia solution (sp. gr. 0910). The dirty-green, thick mass is heated for about half an hour on the water bath, and then the amido- aldehyde is distilled over i n a current of steam. The first 150 C.C. or so of the distillate comes over milky, the succeeding portion is clear, but has a green colour. About 700 C.C. of the distillate are collected, acidified with hydrochloric acid, cooled with ice to Oo, and diazotised wit'h sodium nitrite solution until a drop of the diazo-solution colours a piece of starch iodide paper blue.

The diazo-solution is then transferred to a large flask, and a solu- tion of 10 grams of potassium iodide, in about 50 C.C. of water, added ; an evolution of nitrogen takes place, and iodine separates. After a time, the mixture is heated gently on the water bath until the evolution of nitrogen ceases, and then sulphurous acid is added until the iodine is all reduced. The aldehyde is distilled over with steam, and solidifies in the receiver ; it is purified by shaking with warm, dilute caustic soda solution. On solidifying again it is collected and wzshed with water. Thus prepared it has a melting point of 36'

Ort7Lo.iudobenzaldehyde dichloride may be prepared in the usual manner by passing chlorine through the chloroform solution of the aldehyde.

CI = 23.41. 0.3925 required 25.89 C.C. NjlO thiosulphate solution.

The residue from the titration was ortho-iodobenzaldehyde me1 ting at 36O. On treating some of this dichloride with a concentrated solu- tion of sodium carbonate only a very small quantity of a white substance remained undissolved, and this, as its melting point (36') showed, was ortho-iodobenzaldehjde.

An attempt, was made to prepare the iodoso-aldehyde by t.reating the chloride with a 2 per cent. sodium carbonate solution. One gram of the dichloride was allowed to stand in a mortar with a litfle more than the theoretical quantity of this solution for about two hours, being stirred occasionally ; the yellow colour had then completely disappeared, and the white substance which remained was collected, mashed with water, alcohol, and ether, and dried in

Theory requires C1 = 23.43.

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PATTERSON : IODOSO- AND IODOXY-BENZALUEHYDES. 1007

a desiccator. Only a very smxll quantity was obtained, about 0.1 g ram. T t turned brown on h e a t k g to 2053, and decomposed with intumescence and separation of iodine at, 210'. A titration executed in the usual manner gave the following result.

0.0797 required 6.5 c c. N/10 thiosnlphate solution = 6-52 per cent.

Theory requires 6.45 per cent. of active oxygen. of active oxygen.

The residue from this titration was only precipitated after 24 hours' standing ; it was ortho-iodobcnzoic acid nielting at 148'.

A very small portion of the supposed iodosoaldehyde was shaken up with sulphurous acid in order to reduce the iodosoaldehyde to iodoaldehyde and the recidue collected, maslied with water, and dried. Its melting point was then foiirid to be 3Go, and the substance was, therefore, ortho-iodobenzaldehyde.

A small quantity of substance, prepared as above described, was boiled with water in order to prepare ortho-iodoxybenzalciehyde, but instead of this ortho-iodobenzoic acid was formed.

On acidifying the alkaline filtrate from the iodosoaldehyde with sulphuric acid, a pale yellow precipitate was obtained, which was collected, washed with water, and recrystnllised from hot water. It was strongly active towards potassium iodide, decomposed on heating a t 228O, and was easily soluble in alkalis. After being deconiposed with potassium iodide and acid, a residue of ortho-iodobenzoic acid was left melting a t 155", so that the precipitate from the sodium carbonate solution was ortho-iodosobenzoic acid.

It is, therefore, probable from these experiments tba t ortho-iodoso- benxnldehyde is capable of existence although the yield obtained was too small to enable u s to definitely decide the point, but a t any rate i t is much more difficult to prepare than the meta- and para-iodoso- benzaldehydes, by far the larger part of the chloride used being con- verted into ortho-iodosobenzoic acid.

This fact is interesting when we remember that with the acids, the reverse is the case, ortho-iodosobenzoic acid may be easily obtained whilst the preparation of meta- and para-iodosobenzo'c acids offers considerable difficultp.

As the oximes and phenylh-j-di-azones of ortho-, meta-, and para- iodobenzaldehydes have not been described we have also prepared them.

The three oximes were prepared by the following method. Two parts of the aldehyde are dissolved in alcohol, and to th i s

solution is added one prepared by mixing a solution of 1 part of bydroxylamine hydrochloride in water, and 1 part of potassium carbonate in water. This mixture is allowed to stand for some time,

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1008 PATTERSON : IODOSO- AND IODOXY-BENZALDEHTDES.

when the oxime is precipitated by adding water and recrystallised from dilute alcohol.

Ortho- iodobensaldnxinze forms small, colourless needles, and melts at 107-108".

In an estimaiion of the nitrogen by the magnesite method 0.3893 gave 16.2 C.C. moist nitrogen a t 12" and 757 mm. N = 5 55.

C,HJ*CH:NOH requires N = 5.67 per cent. . Mefu-iodobenzaldoxime also fo rms colourless needles melting at

0.3067 gave 15.3 C.C. moist nitrogen a t 16' and 761 mm. N = 5.82. Theory requires N = 5.67 per cent.

A small quantity of this oxime was dissolved i n chloroform and chlorine passed through the solution, whereupon a peculiar reaction was observed. The solution was at once coloured a deep bluish- green and, if concentrated, it a t first completely absorbed the chlorine. By the continued action of chlorine, the colour passed through various tints, and finally disappeared, bu t before i t was quite gone a white precipitate separated, which became yellow by further treatment with chlorine. This yellow substance was collected and dried, and a weighed portion decomposed with potassium iodide and acid. The separated iodine was then titrated with sodium thiosalphatc.

C6H4(ICl,)*CH:NOH requires C1 = 26.32 per ceut.

I n order to see if this reaction extended also to other oximes some benzaldoxirne was prepared, a portion of it dissolved in chloroform and chlorine passed through the solution. The same colour phe- nomena were observed, but no precipitate was obtained in this case. W e hope soon to have further investigated this reaction.

0.3902 gave 20.2 C.C. moist nitrogen at 19' and 742.5 mm. N = 5.84. Theory requires N = 5.67 per cent.

The phenylhydrazones were prepared by dissolving 2 parts alde- hyde in alcohol and adding t o it an alcoholic solution of 1 part of phenylhydrazine. The mixture was allowed to stand for some time, and ihe hydrazone then precipitated with water, and recrystallised from dilute alcohol.

The percentage of nitrogen for the formula C,H,I*C EI:N-NH*C,H, -is 8-79.

Ortho-iodoBenzaldehydephenylhydrazme crystallises in small, yellow columns, and melts a t 79". 0,2233 gave 18.3 C.C. moist nitrogen a t 12Oand 757 mni. N = 8.57 p c .

62-63'.

0.3146 required 18-11 C.C. N/10 thiosulphate solution. C1 = 20.76.

Para-iodobentaldoxi~ne. Colou rless needles melting at 11 1'.

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TILDEN: THE ACTION OF BROMINE ON PINENE. 1009

Meta- ivdobenzalaehydephenylhydrazone also forms yellow columns which gradually become red in air. 0.2694 gave 20.8 C.C. moist nitrogen at 16" and 761 mm. N = 9.01 p.c.

Pnra-iodobenzn7de~depl~enylhydl-azone. Small yellow columns turning red in air. 0.3239 gave 24.2 C.C. moist, nitrogen at 16" and 754 mm. N = 8.61 p.c.

Melting point 155".

Melting point 121".

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