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766 BALY AND DESCH: ULTRA-VIOLET ABSORPTION SPECTRA OF
LXXVIIL-The Ultra-violet Absor;ption Specty-a of Certain Enol-keto-tautomerides. Part 11
By EDWARD CHARLES OYRIL BALY and CECIL HENRY DESCH. IN the first part of this investigation (Trans., 1904, 85, 1029) the ultra-violet absorption spectra of acetylacetone and ethyl aceto- acetate and of certain derivatives of these compounds were de- scribed. Reasons were brought forward in support of the view that the absorption band obtained in photographing the ultra- violet spectrum of iron through solutions of these substances, according t o Hartley's method, is due to the equilibrium existing between the two possible tautomeric forms. It was found that neither of the modifications, when in a pure state, gives an absorp- tion band, but that when the two are present in equilibrium with m e another, a very decided absorption band is developed. It was further pointed out that the persistence of this absorption band over a definite change of concentration may doubtless be taken as a measure of the relative number of molecules in the changing state. Finally, it was found that the oscillation frequency of the light waves absorbed is nearly the same in all the substances examined, whether these cont'ained a hydrogen, glucinuni, sodium, or even a thorium atom in the so-called labile condition. We therefore concluded that the absorption band cannot in any way be regarded as being directly due t o an oscillating atom, that is to say, the vibration frequency of the atom cannot be the same as the oscillation frequency of the light absorbed. We have now in- vestigated the ultra-violet absorption spectra of the following analogous substances : ethyl acetylsuccinate, ethyl diacetylsuc- cinate, ethyl benzoylacetate, ethyl oxaloacetate, ethyl acetonedi- carboxylate, ethyl benzoylsuccinate, and benzoylacetone, together with certain of their metallic derivatives. The conclusions drawn in the previous paper have been fully confirmed; on the one hand, neither the pure hydroxylie nor the pure ketonic substance shows an absorption band, and on the other hand, the vibration-frequency of the absorption band seems t o bear little relation to the mass of the atom in the labile state.
Only three of the substances dealt with in the present paper exhibit absorption bands in the free state, namely, benzoylacetone, ethyl benzoylacetate, and ethyl benzoylsuccinate. It is evident, therefore, that there must be in these three cases a considerable number of molecules in the oscillating state, whilst in the case of the remaining substances dealt with, almost all the molecules are Probably quiescent; it is not possible t o say with any certainty
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CERTAIN ENOL-KETO-TAUTOMERIDES. PART 11. 767
whether the latter substances are enolic or ketonic, but it is probable, from a comparison of their absorption curves with those of acetonylacetone and ethyl ethoxyfumarate, that they are chiefly enolic.
The conclusion that the pure substances do not show any absorption band in their spectra is based on the results obtained with acetonylacetone, ethyl ethoxyfumarate, and hydroxy- methylenecamphor. The details of the absorption spectra are given below, and it will be seen that there is no semblance of an absorption band developed in any of these substances. In acetonyl- acetone we have a purely ketonic compound, in ethyl ethoxy- fumarate a derivative of the purely hydroxylic form of ethyl oxaloacetate, and in hydroxymethylenecamphor we have an analo- gous condition in the hydrosymethylene group. It may be pointed out that solutions of camphor itself of the strength we work with have been shown by Hartley t o be quite diactinic, so that we are justified in attributing the absorption given by this substance entirely t o the presence of the hydroxymethylene group.
With the exception of the aluminium derivatives of ethyl benzoylacetate and benzoylacetone, we have only been able to in- vestigate the free compounds and their sodium derivatives ; but, as can readily be seen from the experimental results given below, although the absorption bands are usually shifted towards the red in the metallic derivatives, the amount of shift is by no means the same in all the substances, and bears no simple relation to the masses of the metallic and hydrogen atoms. The slight shift- ing observed is only what would be expected from the small in- crease in the total mass of the molecule, as has so many times been pointed out by Hartley.
I n attempting t o find an explanation of the origin of the absorp- tion band it is necessary to take a different view of the physical process from that usually held. It is perfectly evident that some vibration or free period must exist connected with the transition from one tautomeride t o the other, which is synchronous with the oscillation frequency of the light rays absorbed. There seems to be no question of doubt that this vibration cannot be the vibration of the labile atom itself, for, apart from the fact that the oscillation- frequency of the absorption band bears little relation to the mass of this labile atom, it is also noteworthy that the oscillation- frequency of the band is far greater than that usually attributed to atomic motions. We are therefore driven t o the conclusion that the absorption of light is due to the change of linking expressed by the following reversible equation :
-CH,*CO- 22 -CH:C(OH)-,
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'768 BALY AND DESCH : ULTRA-VIOLET ABSORPTION SPECTRA. OF
and not merely to the wandering of the labile atom. This may be expressed in another way by saying that the phenomenon is due to the change of condition of the two carbon atoms and the oxygen atom. If we consider in detail the transition from, for example, the enolic to the ketonic form, it will be seen that the hydrogen or other labile atom leaves the oxygen and wanders to the carbon atom; there must, however, obtain for an exceedingly short time a condition in which the hydrogen atom is half-way on its journey, when we cannot consider it t o be definitely linked either to the oxygen or to the carbon atom. We may thus conceive the momentary existence of an intermediate transition phase, which can be expressed thus:
-CH*F- H O
During the existence of this transition phase the two carbon atoms and thf oxygen atom are actually changing their linking. It seems probable that the absorption band is due t o this change of linking, or, in other words, i t is due to the above transition phase. It must not be forgotten that the oscillation-frequency of the absorption band appears to be too great to be connected in any way with the motions of the atoms qu& atoms, and therefore we are not able t o attribute it t o possible motions of the carbon or oxygen atoms.
I n attempting t o form a theory to account for the connection between the change of linking and the absorption of light, it is necessary to take account of certain facts which have been estab- lished experimentally by Hartley and others in this field. Firstly, no organic substance shows an absorption band unless a possibility of tautomerism exists in the molecule. Secondly, this tautomerism need not be due t o a labile atom, but may be of the same order as that occurring in those aromatic substances containing the true benzenoid structure. Thirdly, in all cases of the simpler tauto- meric molecules, the vibration-frequencies of the absorption bands are very nearly the same. Fourthly, an increase in the mass of the molecule causes a decrease in the oscillation-frequency of the absorption band.
Finally, we h-ave Hewitt's theory of fluorescence, namely, that this phenomenon is due to a process of tautomerism. If this is accepted, it appears that a tautomeric substance is not only able t o give rise t o a selective absorption of light, but also in certain circumstances to act as a source of light.
Up to the present no theory has been brought forward to account for any of these facts, but it is possible to co-ordinate all of them,
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CERTAIN ENOL-KETO-TAUTOMERIDES. PART 11. 769
and a t the same time to explain the formation of the absorption bands by the same theory as that employed by physicists to explain the phenomena of radioactivity, emission spectra, series of spectral lines, the Zeeman effect, &c., namely, the electron theory. This theory postulates that each atom is a system of small particles or electrons, which are in continual motion round a common centre of gravity, and that the emission spectra of gases are due to vibra- tional disturbances of these systems of electrons. The combination between two atoms is accompanied by the passage of one or more electrons from one atom to the other, producing one or more Faraday tubes of force between them, each Faraday tube represent- ing the chemist’s single bond. I f , by some means, we cause a rearrangement of these linkings or Faraday tubes, it is clear that there must occur a vibrational disturbance in the system of electrons. I n all cases of tautomerism, the rearrangement of the linkings is the essence of the process, and therefore we should expect to find vibrational disturbances in the electrons of the atoms concerned. Now, we have direct evidence of these disturb- ances in the fluorescence of tautomeric substances, as shown by Hewitt. It is therefore only natural that the converse takes place, namely, the absorption of light by tautomeric substances. I n the substances dealt with by us, a t least three atoms in each molecule are undergoing change of linking, and therefore each one of these, owing to the resulting disturbance of the electrons, helps in the formation of the absorption band.
This theory of the formation of the absorption bands accompany- ing tautomerism is capable of bringing into line the facts observed in the ultra-violet absorption spectra, which were mentioned above. Firstly, the fact that the oscillation-frequencies of the absorption bands given by simple tautomeric substances are always very nearly the same-the changes of linking taking place are all of the same type, whether in the aromatic compounds containing the benzenoid nucleus o r in the aliphatic tautomerides, and therefore the same type of vibrational disturbance on the electrons is set up, resulting in approximately the same frequency in the absorption band. Secondly, an increase in the mass of the molecule causes the oscilla- tion-frequency of the band to decrease, and the band is shifted towards the red; the period of the vibrational disturbance of the electrons depends on the mass of matter in their immediate neighbourhood, and becomes slower when this mass is increased. This decrease in the period of the vibrations of the electrons, with increase in the mass of the molecule, is well shown by the spectral series of the several elements of the same family. This can be
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770 BALY AND DESCH: ULTRA-VIOLET ABSORPTION SPECTRA OF
seen a t once from the following equations for the first members of the principal series of the alkali metals, where m is the oscillation- frequency, and m the number of the line in the series (= 3 , 4 , 5, kc.).
133669 - 1100084 m2 nz 4
130233 - 800791 nz4 9122
........... Lithium n = 43584.75 -
Sodium ) t = 4'1542 51 - -- _ _ - - ............... 126983 625318 Potassium ......... N = 35086.55 . --- . - ~ .
'HLJ m4
Rubidium ............ 125395 - 486773 Cmiuni ............... I L = 31509.31 - ~ _ _ _ _ ~ - ~
??id 1124
These equations of Kayser and Runge show a t once how the series is in each case bodily shifted towards the red with increasing mass. We have in this a very striking analogy between emission and absorption spectra.
The chemical aspect of tautomerism, as seen in the light of ultra- violet absorption spectra, is also very interesting. For example, solutions of the sodium and aluminium derivatives of ethyl aceto- acetate are equilibrium mixtures of the enolic and ketonic modifi- cations, that is to say, the sodium and aluminium atoms respectively are oscillating between the two positions. Now, in the case of the sodium compound, there is distinct evidence of ionisation and hydrolysis, but in the case of the aluminium compound the ionisa- tion and hydrolysis are very small. Now, Hartley (Trans., 1902, 81, 571; 1903, 83, 221) showed that metallic nitrates and nitric acid in solution give absorption bands, the position of which depends on the mass of the metal. These bands, however, are only developed in solutions which, according to the electrolytic dissociation hypo- thesis, are ionised, and Hartley, in this way, showed that there must be intimate connection between the metallic atom and the NO, group, even in dilute solutions, when the salts are more or less completely ionised. Even without this discovery of Hartley's, i t is impossible t o conceive of the bond of chemical attraction, or the Faraday tube between the two ions of a metallic salt, as being destroyed by simple solution. It would seem preferable t o consider the action of the solvent as merely tending to draw the two ions apart. When the two ions are sufficiently separated t o allow of an interchange of ions between different molecules, we then have the condition called ionisation. I n this way, we do not picture the bands of affinity as being destroyed, but merely broken in one place and regenerated in another. It is possible, on these lines, to consider the whole phenomena of electrolytic dissociation from a far broader standpoint, When a compound is dissolved, the
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CERTAIN ENOL-KETO-TAUTOMERIDES. PART 11. 771
tendency of the solvent is t o separate the molecules into two or more ions. When the ions become sufficiently far removed from one another t o permit of the interchange of ions between adjacent molecules, we have the condition of ionisation, which is partial, or more or less complete, according as to whether the interchanges are small or great in number per unit time. When, however, the separation of the ions has not reached the critical length, no inter- change takes place, and we have the non-ionised condition, for example, mercuric cyanide in water. I n this class we might in- clude the many organic compounds which apparently react by ions, even although their solutions show little or no evidence of ionisation (compare Kahlenberg, J . Physical Chem., 1902, 6, 1). One class more may be included, namely, the aliphatic tautomeric substances, which may be regarded as being only sufficiently dis- sociated in solution t o allow of interchanges between different parts of the same molecule. The labile atom is in a state of incipient dissociation, and may thus be looked upon as a potential ion.
The whole question of dissociation thus appears t o be one merely of degree and not of kind, and there is no need to consider any discontinuity in the action of the solvent.
It is possible t o put this view to the test in the case of the aliphatic tautomeric substances. We have already suggested that the persistence of the band is a measure of the number of molecules which are in the transitional state between the two forixs; on the above view, this persistence is a measure of the extent to which the labile atoms are separated from the rest of the molecule.
There should exist, therefore, for every tautomeric substance, a maximum value of this persistence which corresponds to the con- dition that the separation of all the labile atoms from the rest of the molecule has overstepped the critical value, and that perfectly free interchanges are taking place. Now, we have shown that the addition of sodium hydroxide increases the persistence of the absorption band ; successive additions of the alkali should there- fore increase the persistence until the maximum value is reached, and the amount of hydroxide necessary to produce this should be far beyond that required t o convert the whole of the substance into the sodium derivative. This is well evidenced by the addition of sodium hydroxide to the aluminium derivative of ethyl benzoyl- acetate, a large excess being necessary to produce the maximum persistence (compare Fig. 1). We have investigated the action of sodium hydroxide on ethyl benzoylsuccinate and have observed the absorption spectra of the substance in the free state and in the presence of one, ten, twenty, and one hundred equivalents of alkali.
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772 BALY AND DESCII: ULTRA-VIOLET ABSORPTION SPECTRA O F
The measurements of the persistence of the absorption band in each case are as follows:
With 1 CQ. With 10 eq. With 20 eq. With 100 eq. Free ester. of alkali. of alkali. of alkali. of alkali.
a t ........................ 120 intn. 63 mm. 40 mm. 31.7 mm. 21-9 mni. Absorption band begins
Absorption band ends a t 83.2 ,, 34’7 ,, 20 ,, 15.2 ,, 10.4 ,, Chango of dilution over
which absorption band persists ......... 30.7 % 44.9 % 50 % 52 % 52.5 %
The thicknesses given refer to a N/lO,OOO solution of the ester. These results leave little doubt that the persistence of the absorp-
tion band is steadily increased by the addition of alkali until a maximum is reached; in the case of ethyl benzoylsuccinate, the maximum is apparently reached by the addition of 20 equiva- lents of sodium hydroxide, as an increase in the alkali to 100 equivalents only increases the persistence by 0.5 per cent.
Ex P E R I M E NT A L.
Benxoylacetone.
This substance was obtained from Kahlbaum, and another speci- men was prepared for us by Messrs. A. C. Carter and D. B. Byles. Both specimens were found t o be pure after recrystallisation from alcohol. Solutions were made in absolute alcohol, and their absorp- tion spectra photographed. The following measurements of the absorption band were obtained :
0.162 gram (1 milligram-molecule) in 1000 C.C.
Thickness of layer of solution in millimetres. Description of spectrum.
60 Spectrum transmitted to ............ 40 ........... 30 ............ 20 ............ 10 ............
9 ............ a ............
Absorption band.. ............... Spectrum transmitted (weak) ......
6 Spectrum transmitted to ............
9 , 9 9
, J 9 9
> 9 Y ,
9 , 9 ,
9 ) > r 9 9 7 ,
Complete absorption beyond.
Absorption band .................. Spectrum transmitted ............... Complete absorption beyond.
4 Spectrum transmitted to ............ Absorption band.. ................ Spectrum transmitted ...............
‘/A. 2810 2815 2820 2830 2860 2865 2875
2875-3800 3800-3850
2900 2900-3748 3748-3875
2935 2935-3640 3640-4140
A. 3557 3552
3532 3496 3490 3477
3477-2630 2630-2597
3447 3447-2667
-
2 ~ ~ 7 - 2 5 ~ 0
3405 3405-2746 2’746-2415
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CERTAIN ENOL.KICTO.TAUTOMERIDES. PART 11 . 773
0.162 gram in 10. 000 C.C. Thickness of
layer of liquid in millimetres . Description of spectrum . '/A .
30 Spectrum transmitted to ............ 2970 Absorption band ................ 2970-3558 Spectrum transmitted ............... 3558-4290 Complete absorption beyond . Absorption band .................. 3030-3480 Spectrum transmitted ............... 3480-4320 Complete absorption beyond . Absorption band .................. 3200-3300 Spectrum transmitted .............. 3300-4340 Complete absorption beyond .
25 S )ectrum transmitted to .......... 3030
20 Spectrum transmitted to ............ 3200
10 Spectrum transmitted to ............ 4390
A . 3366
3366-2810 2810-2330
3299 3299-2873 2873-2314
3124 31%-3029 3029-2303
2277
Ben x og Zuce tone in presence of Sodium B y droxide . 0.162 gram in 1000 C.C.
Thickness of layer of liquid in millimetres . Description of spectrum . ]/A .
8 Spectrum transmitted to ............ 2805 6 .......... 2810
Absgrption b a h .................. 2810-3500 Spectrum transmitted ............... 3500-3900 Complete absorption beyond . Absorption band .................. 2835-3400 Spectrum transmitted ...............
4 Spectrum transmitted to ............ 2835
3 400-38 60
0.162 gram in 10. 000 C.C. Thickness of
layer of liquid in millimetres . Description of spectrum . '/A .
30 Spectrum transmitted to ............ 2890
20 ) ) to ............ 2970
15 .. to ............ 3020
10 9 7 ) ) to ............ 4310 8 7 > ) ) to ............ 4360
) ) ) ) to ............ 4460
Absorption band .................. 2890-3305 Spectrum transmitted ............... 3305-4030
Absorption band ................. 2970-3220 Spectrum transmitted ............... 3220-4190
Absorption band .................. 3020-3140 Spectrum transmitted ............... 31 40-4247
.. 7 9
6
Ben3 oy lac e t one. A Izcnainium D emha tiv e .
A . 3565 3558
3558-2857 2857-2562
3526 3526-2938 2938-2589
A . 3459
3459-3024
3366 3024-24ao
3366-3104 3104-2384
3309 3309-3184 3184-2354
2319 2293 2241
The aluminizcm derivative of benzoylacetone. Al(CloH902)3. is readily prepared by adding an alcoholic solution of benzoylacetone (3 mols.) to a solution of aluminium chloride (1 mol.) and sodium acetate (3 mols.) in watm . The aluminium derivative separates
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774 BALY AND DESCH: ULTRA-VIOLET ABSORPTION SPECTRA OF
inimediately as a crystalline precipitate. It dissolves very spar- ingly in organic solvents, but may be recrystallised from a large volume of hot alcohol. It melts a t 217*, but after being allowed to solidify again melts a t 1 6 2 O .
0.170 gram (1 milligram-equivalent) in 1000 C.C.
Thickness of lager of liquid in millimetres.
8 6
4
Thickness of layer of liquid in millinietres.
30
25
20
10
9
8
The free colourless. by mixing
Description of spectrum. ' /A. A.
Spectrum transinitted t o ............ 2800 3570 2 ) 9 7 ............ 2805 3565
Absorption band.. ................ 2805-3630 3565-2755 Slmtrum transmitted . . . . . . . . . . . . . . . 3630-3750 2755-2666
) ) to . . . . . . . . . . . . 2810 3557 Absgrption band.. . . . . . . . . . . . . . . 2810-3560 3557-2809 Spectrnm transmitted . . . . . . . . . . . . . 3560-3800 2809-2631
0.170 gram in 10,000 C.C.
Description of spectrum. l / A . A. Spectrum transmitted to . . . . . . . . . . . . 2830 3532 Absorption band.. . . . . . . . . . . . . . . . . 2830-3480 3532-2873 Spectrum transmitted . . . . . . . . . . . . 3480-3870 2873-2583
Absorption band.. . . . . . . . . . . . . . . 2855-3445 3501-2902 Spectrum transmitted . . . . . . . . . . . 3445--3980 2902-2511
Absgrption band.. . . . . . . . . . . . . . . . 2905-3400 3441-2938 Spcctrum transmitted . . . . . . . . . . . . . . . 3400-41 55 2938-2406
> > 3333 ), to . . . . . . . . . . . 3000 Absorption band.. ................ 3000--3230 3333-3094
,} to ............ 3040 3288 Absorption band.. . . . . . . . . . . . . . . . 3040-3190 3288-3133
Spectrum transmitt,vd to . . . . . . . . . . . 4420 2262
) } to . . . . . . . . . . . . 2855 3501
to . . . . . . . . . . . 2905 3441
Spectrum transmitted . . . . . . . . . . . . . 3230-4270 3094-2341 $ 9
Spectrum transmitted ............... 3190-4350 3133-2298 Spectrum weak ........................ 3080-3120 3246-3204
Etlq 2 Bmxo y Zucetate, COPli* CH,. C0,Xt.
ester was obtained from Kahlbaum and was perfectly The aluminium derivative, Al(CllHl103)3, was prepared an alcoholic solution of the ester (3 mols.) with an
aqueous solution of aluminium chloride (1 mol.) and sodium acetate (3 mols.), alcohol being added t o dissolve any precipitate which may be formed. The aluminium derivative separates after a time as a viscous oil, which slowly solidifies, and may be recrystallised from hot alcohol, in which i t is rather sparingly soluble; it melts sharply at 135'. The absorption curves of these substances are shown in Fig. 1, in which curve 1 is that of the free ester, curve 2
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CERTAIN ENOL-KETO-TAUTOMERIDES. PART 11. 775
is that of the aluminium derivative, curve 3 that of the ester in the presence of sodium hydroxide, and curve 4 that of the aluminium derivative in presence of sodium hydroxide.
Oscil Zation frequencies.
8 3000 2 4 6 8 4000 2 4
Et h y I A cet onedicarb ox ylat e.
The substance, which was obtained from Kahlbaum, was quite colourless; it was twice redistilled and boiled at 167' under 45 mm. pressure.
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716 BALY AND DESCH: ULTRA-VIOLET ABSORPTION SPECTRA OF
The Ester in presence of Alkali Hydroxide.
0-202 gram (1 milligram-molecule) in 100 C.C.
Thickness of layer of liquid in millimetres. Description of spectrum. '/A. A.
30 Spectrum transmitted to ............ 3220 3105 20 ........... 3250 3076 10 > > 7 7 ............ 3280 3048
8 > > 9 ) ........... 3295 3034 6 > 9 , ............ 3305 3025 4 7 7 Y ? ........... 3335 2997
) 7 >,
0.202 gram in 1000 C.C.
Thickness of layer of liquid in millimetres.
30 20 10 8 7
6
4
3
2.5
2
Description of spectrum. l/?L
Spectrum transmitted to ............ 3353 ............ 3370 ............ 3400
Y ) 9 2 ........... 3418 7 9 ............ 3425
Absorption band.. ................ 3425-4040 Spectrum transmitted ............... 4040-4220
), to ............ 3437 Absorption band.. ................ 3437-3980 Spectrum transmitted ............... 3980-4290
9 , ,, to ............ 3473 Absorption band.. ................ 3473-3880 Spectrum transmitted ............... 3880-4410
9 , ), t o ............ 3520 Absorption band .................. 3520-3800 Snectrum transmitted ............... 3800-4415
, 7 3 7
7 7 9 ,
7 7
Y ) ,, to ........... 3565 Absorption band.. ............... 3565- 3750 Spectrum transmitted ............. 37 50-441 7 Spectrum weak ....................... 3600-3700 Spectruiii transmitted to ............ 4420
A. 2982 2966 2940 2925 2919
2474-2369 2908
2919-2474
2908-2512 2512-2330
2879 2879-2577 2577-2267
2840 2840-2631 2631-2265
2804-2666 2666-2263 2777-2702
2804
2262
Ethyl A ce t onedicarb oxylat e .
0.202 gram (1 milligram-molecule) in 100 C.C.
Thickness of layer of liquid in millimetres. Description of spectrum. '/A. A.
30 Spectrum transmitted to ............ 3557 2810 20 9 ) 7 , ............ 3600 2776 10 ,> 9 % ............ 3660 2731 8 ?, > 7 ............ 3668 2716 6 ? ? > > ............ 3685 2712 4 Y Y 7 , ............ 3725 2684
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CERTAIN ENOL-KETO-TAUTOMERIDES. PART 11. 177
0.202 gram in 1000 C.C.
Thickness of layer of liquid in millimetres. Description of spectrum. '/A.
30 Spectrum transmitted to ............ 3765
10 ............ 20 > > 9 2 .......... 3835
IY > Y 4040 8 > > Y > ............ 4140 6 > > 9 ) ............ 4200 5 > > > > ............ 4280
> > > Y 4390 4 ............
A. 2655 2607 2474 2415 2380 2336 2277
E t h y l Oxaloacetate,
The sample employed was obtained from Kahlbaum; it was colourless, and when redistilled under 27 mm. pressure boiled at 132-133'.
0.188 gram (1 milligram-molecule) in 100 C.C. of alcohol.
Thickness of layer of liquid in millimetres. Description of spectrum. IJA. A.
30 Spectrum transmitted to .......... 3225 3100 20 9 2 1 s ............ 32TO 3057 10 > ) 9 9 ............ 3345 2988 8 3 ) > 3 ............ 3360 2976
) > 2 ) 3365 2971 4 ) > > > ............ 3390 2950 6 ............
0-188 gram in 1000 C.C. of alcohol. Thickness of
:layer of liquid Sn millimetres.
30 20 15 10 8 6 5 4
Description of spectrum. Spectrum transmitted to ...........
> ) Y >
> > > > > I > > ) I 9 )
2 7 > > > > > Y
9 ) 2 )
...........
............
............
............
............
............
............
I/A.
3405 3420 3470 3560 3730 4005 4200 4365
A d
2934 2923 2881 2808 2680 2496 2380 2290
VOL. LXXXVII,
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778 BALY AND DESCH : ULTRA-VIOLET ABSORPTION SPECTRA OF
Ethyl Ozaloncetute i i ~ A Zkaliirze Solutiort.
0.188 gram in 100 C.C. of alcohol. Thickness of
layer of liquid in millimetres. Description of' spectrum. ]/A. A .
30 20 10
8
6
4
3
2.5
2
Spcctrum tralismitted to ...........
Absgrption band.. ................
Absdrption band.. ............... Spectrum tmmistnitted ..............
,, to ............ Absorption band.. ............... Spectrum transmitted . . . . . . . . . . . .
to . . . . . . . . . . . Absorption band.. . . . . . . . . . . . . . . Spectrum transmitted . . . . . . . . . . . . . . .
) ) to . . . . . . . . . . . . AbsGrption band.. ................ Spectrum transmitted ...............
), to ............ Absorption band.. . . . . . . . . . . . . . . Spectrum transmitted . . . . . . . . . . Spectrum weak ....................... Spectrum transmitted t o ............
> > 9 7 ........... . . . . . . . . . .
Spectrum transmitted ............... 3 ) ) to ............
7 7
2830 2875 2055
29554050
2980 4050-4170
2980--3960 3960-4245
3010-3860 3010
3860-4310 3070
3070-3720 3720-4400
3130 3130-3610 3610-4460
3210-3515 351 5-451 0 3300- 3420
3210
4540
3352 3477 3383
3383-2468 2468-2397
3355 3355-2524 2524-2355
3321 3321-2590 2590-2319
3256 3256-2687 2687-2272
3194-2769 2769-2241
31 14-2844 2844-2217 3030-2923
2202
3194
3114
Etlql Ethoxyfunzrcrctte, CO,Et*C(OEt):CH*CO,Et. This substance was very kindly supplied to us by Dr. Lander,
and its absorption spectrum is of especial interest, as the compound may be regarded as a derivative of the enolic form of ethyl oxalo- acetate. The specimen boiled a t 135-137' under 11 mm. pressure.
0.216 gram (1 milligram-molecule) in 100 C.C. of alcohol. Thickness of
layer of liquid in milliinetres. Description of' spectrum. ' /A. A.
30 Spectrum transmitted to ............ 3260 3067 9 7 > 3039 20 .......... 3290
10 ........... 3350 2984 8 7 1 > 7 3360 2975 6 ............ 3370 2966
9 7 > 7 2940 4 ............ 3400
7 ) 9
............ , >
0.216 gram in 1000 C.C. Thickness of
layer of liquid in millimetres. Description of spectrim. l /A .
30 Spectruin transmitted to ........... 3433 20 ............ 3500 15 ............ 3550 10 .......... 3645
7 ) > ? 3680 8 ............ 6 ............ 3720 4 . . . . 3840
3 ) > )
> 7 > )
> ? I >
9 ) 7 )
>
A. 2912 2856 2816 2742 27 17 2687 2604
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779 CERTAIN ENOL-KETO-TAUTOMERIDES. PART rr.
0.216 gram in 10,000 C.C. Thickness of
layer of liquid in millimetres. Description of spectrum. '/A. A.
30 Spectrum transmitted to ............ 3900 2563 20 Y ? 4030 2481 10 7 7 Y Y ........... 4190 2386 8 > > Y * ............ 4235 2361 0 Y Y 4270 2341 4 3 ) Y > 4355 2296
$ 7 ...........
9 7 ............ ............
E~hyZ Acetylsuccinate, C0,Et *CH Ac*CH,-CO,Et.
This substance was obtained from Kalilbaum and on being dis- tilled boiled a t a constant temperature.
Free Zster.
0.216 gram (1 milligram-molecule) in 100 C.C. of alcohol.
Thickness of layer of liquid
i n rrrillimetres. Description of spectrum. 30 Spxtruni transmitted to ............ 20 ............ 10 ............ 8 ........... 0 ............ 5 ............ 4 ............ 2 ..........
9 ) ? ?
I > 9 Y
3 ) 3 )
9 ) 1 )
9 ) Y l
Y ? ? ?
9 , 9 3
I/A.
3550 3640 3740 3825 3940 4000 4030 4040
A. 2816 2746 2673 2614 2537 2499 2481 2474
0.216 gram in 1000 C.C. Thickness of
layer of liquid in millimetres. Description of spectrum. ]/A. A.
1 5 Spectrum transmitted to ............ 4220 2369 10 9 9 Y > ............ 4400 2272
8 t h y l Acety7siccci.nate in presence of d l k a l i Hydroxide.
0.216 gram in 100 C.C.
Thickness of layer of liquid in millimetres.
30 20 10 8 6 4
Description of spectrum. '/A. A. Speetrurn transmitted to ............ 3140 3183
? > Y 9 ............ 3170 3153 7 1 Y Y 3106 9 ) 9 7 ............ 3240 3085 Y Y ¶ * ............ 3260 3067 7 9 Y Y
3062
............ 3220
............ 3265
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780 BALY
Thickness of layer of liquid
in millimetres. 20 10
8
6
4
1 *5
1
AND DESCH : ULTRA-VIOLET ABSORPTION SPECTRA OF
0.216 gram in 1000 C.C.
Description of spectrum. Spectruni transmitted to ............
Y ? 1 Y .......... $ 9 9 ............
Absorption baid.. ................ Spectrum transmitted ...............
), t o ........... AbsbkpBion band .................. Spectrum transmitted ..............
to ............ Absgrptibn bagd .................. Spectrum transmitted ...............
9 9 ,) t o Absorption band.. ................ Spectrum transmitted ..............
9, ,, to ............ Absorption band.. ................ Spectrum transmitted ............... Spectrum weak ........................ Spectram transmitted to ............
............
p. 3290 3340 3355
3355-3980 3980-4160
3365-39 10 3910-4235
3390-3900 3900-4300
3420-3800 3800-4470
3365
3390
3420
3470 3470-3750 3750-4500 3500-3700
4530
A. 3039 2993 2980
2980-251 2 2512-2403
2971 297 1-2557 2557-236 1
2947 2947-2563 2563-2324
2923 2923-2631
2881 2881-2666
2631-2236
2666-2221 2856-2702
2207
EthyE Dicccetylszcccinate, CO,Et*CHAc* CHAc* C0,Et.
This substance was obtained from Kahlbaum in the form of quite white and well-formed crystals melting at 87'.
Free Ester.
0.27 gram (1 milligram-molecule) in 100 C.C. of alcohol.
in millimetres. Description of spectrum. l /A. A.
Thickness of layer of liquid
30 Spectrum transmitted t o ............ 3370 2966 20 , Y Y J ............ 3405 2985 10 Y , Y ) ............ 3470 2881 8 7 , > 9 ............ 3500 2856 6 $ 9 Y ) ............ 3533 2829 4 $ 9 Y , ............ 3560 2808
0.27 gram in 1000 C.C.
Thickness of layer of liquid in millimetres. Description of spectrum. l /A.
30 Spectrum transmitted to ............ 3570 20 9 9 9 ) ............ 3590 10 ............ 3680 8 ............ 3720 6 ............ 3770 4 3 ) I 9 ............ 3840
9 , >, > ) > ?
$ 9 > 9
A. 2801 2786 2717 2687 2652 2603
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CERTAIN ENOL-KETO-TAUTOMERIDES. PART 11. 781
0.27 gram in 10,000 C.C. Thickness of
layer of liquid in millimetres. Description of spectrum. '/A.
30 Spectrum transmitted to ............ 3870 20 9 1 1 1 ............ 4030 10 3 , 1 3 ........... 4295
9 ; * ) ............ 4375 6 9 ) ? 2 ............ 4490 i3
Ester in presence of A Zkali Zydroxide.
0-27 gram in 10,000 c,c, Thickness of
layer of liquid in millimetres. Description of spectrum. l/A.
30 Spectrum transmitted to . . . . . . . . . . 3193 9 , ............ 3270
2g Absbkption band .................. 3270-4000 Spectrum transmitted .............. 4000-4240
15 ? > ., t o 3340 Absorption band ................. 3340-3844) Spectrum transmitted ............... 3840- 4400
10 9 ) ,, to 3400 Absorption band .................. 3400-3800 Spectrum transmitted ............... 3800-4400
8 Y ? ,, t o 3455 Absorption band.. ................ 3455-3740 Spectrum trarisniitted ............... 3740-4490
6 Spcctruni weak ........................ 3500-3700 Spectrum transmitted to ............ 4520
............
............
............
A. 2583 2480 2328 2285 2227
A. 3131 3057
3057-2499 2499-2358
2993-2603 2603-2272
2993
2940 2940-2631
2893 2631-2272
2893-2673 26'73-2227 2856-2702
2212
Ethyl Benxoylsuccinate, CO,Et*CH(COPh)*CH,*CO,Et.
This substance was obtained from Kahlbaum, and was perfectly colourless. The absorption curves of the ester in the free state and in the presence of 1, 10, 20, and 100 equivalents are shown in Fig. 2, curves 1, 2, 3, 4, 5 respectively.
A. eetonylacetone.
0.114 gram (1 milligram-molecule) in 100 C.C.
Thickness of layer of liquid in millimetres.
30 20 10 8 6 4 3
Description cf spectrum. '/A. Spectrum transmitted t o ............ 3960
7 1 > > 1 ) 1 1
1 ) > 9
9 9 > > 1 3 $ 7
Y > 9,
............ 4030
............ 4110
............ 4150
............ 4205
............ 4280
............ 4360
A. 2525 2480 2432 2409 2377 2335 2293
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7 82 BALY AND DESCH : ULTRA-VIOLET ABSORPTION SPECTRA OF
H ydroxp nz e t h yl elzeca in phor. This substance was kindly supplied t o us by Dr. 31. 0. Forster.
0-180 gram (1 milligram-molecule) in 100 C.C. of alcohol.
i n millimetres. Descriptioii of spectruin. l /A . A .
Thickness of layer of liquid
30 Spectrum transmitted t o ............ 3060 3267 20 9 9 ) 3128 3196 10 . . . . . . . . . . . 3335 2997 8 . . . . . . . . . . . 3355 2979 6 f Y > 9 3370 2966 4 ............ 3391 2948
O s c i l l d i o i ~ freqiiimcies. 8 3000 2 6 8 4000 2 4 ti
........... 7 9 > 9
7 ) > > . . . . . . . . . .
> ) > >
FIG. 2.
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CERTAIN ENOL-KETO-TAUTORIERIDES. P A R T 11. '783
Thickness of layer of liquid in millimetres.
30 20 10
8 6 4 3 2.5 2 '2 2 1.5
0.180 gram in 1000 C.C.
Ilescription of spectr~un. '/A.
Spectrum traiisinitteii t o ............ 3400
9 3 1 ............ 3470 > > 9 9 3490 3 3 7 3515 9 9 7 ) 3553 9 s 9 9 3650
9 > 3 > 4140 > 1 > * 4295 1 ) 3 ) 4400
> 1 7 ) ........... 3430
. . . . . . . . .
............
. . . . . . . . . .
............ > I 1 9 ............ 3510
............ ............ . . . . . . . . . .
A. 2941 2914 2881 2864 2841 2814 2139 2624 2415 2327 2272
cyO?~CI1LLS ions.
I n discussing the conclusions which may be drawn from these results it must a t once be mentioned that they only refer to the conditions under which the substances exist in soiutions of con- centrations varying from *Y/ 100 to N / 10,000 ; whether the same conditions exist with the pure substances cannot, of course, be de- finitely concluded from our experiments. There is, however, no reason why the constitution of the pure substance should be ex- pected t o differ materially froin that in solution.
The following conclusions may be drawn: 1. I n the case of the aliphatic tautomeric substances, neither the
pure ketonic nor the pure eiiolic form gives an absorption band. 2. I n solutions of the strengths dealt with by us the pure ketonic
form is almost diactinic, whilst the pure enolic form exerts a small general absorption.
3. When an absorption band is given, i t nieans that the ketonic and enolic forms are coexistent and in dynamic equilibrium with one another-that is to say, a number of the molecules are oscil- lating between the two conditions. 4. The persistence of the absorption band, that is to say, the
relative change of dilution or of thickness of t'he solution during which the absorption band can be observed, is a measure of the number of molecules in the changing state.
4a. I n order that the absorption band niay be developed i t is probably necessary that a coiisiderable number of the molecules must be in the changing state.
5. The addition of alkali tends t o increase the persistence of the band, whilst the addition of acid tends to decrease it.
6. The successive increase of alkali increases the persistence of the band until a maximum is reached, beyond which the further addition of alkali does not increase it.
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784 McINTOSH: THE BASIC PRQPERTIEB OF
7. The absorption bands are given by the aluminium derivatives of the tautomeric substances as well as by their sodium derivatives; the former compounds are soluble in alcohol, and are neither hydro- lysed nor ionised.
8. The oscillation-frequency of the absorption band bears no relation to the mass of the atom in the labile state.
9. The absorption band is due to the change of linking accom- panying the change from the one form t o the other, and its forma- tion niay be explained by the modern physical conception of the atom as a system of electrons.
10. The labile atom may be regarded as a potential ion, inas- much as the bond of attraction o r Faraday tube of force must be considered to be lengthened sufficiently to allow of the interchange of the atom from the one position to the other within the molecule; fhe action of alkali and acid may thus be considered to have the effect of lengthening or shortening these tubes of force, thereby increasing or decreasing the number of interchanges taking place in unit time.
11. This view may be taken of salts in solution, that the bonds of attraction connecting the “ ions” together are lengthened by the solvent. When the length of the Faraday tubes is below a certain critical length, the salt is (( non-ionised.” When the average length of the tubes of force is equal to or a little less than the critical length, a few interchanges of ions between adjacent molecules take place, and the salt is partially ionised. When the length of the Faraday tubes is greater than the critical value, then perfectly free interchange takes place between the ions of different molecules, and She salt is completely (( ionised.”
SPECTROSCOPIC LABORATORY, UNIVERSITY COLLEGE, LONDON. Pu
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