Sulfonic Acid Derivatives of 1,lO-Phenanthroline DAVID E. BLAIR and HARVEY DIEHL Department o f Chemistry, Iowa State University, Ames, Iowa Sulfonation of 1 ,1 0-phenanthroline has been effected b y fusion with ammonium acid sulfate a t 365' C. 1 , l O Phenanthroline 5 -sulfonic acid and 1 ,I 0-phenanthroline-3-sulfonic acid have been isolated and characterized. Both acids form red ferrous compounds having about the same spectrophotometric characteristics as the ferrous derivative of 1 ,I O-phenanthroline; the perchlorates of the ferrous compounds of the sulfonated materials are soluble, however, and this makes possible the determination of iron in the perchloric acid solutions following wet ashing with perchloric acid. Sulfonation, like nitration, raises the potential a t which the red ferrous phenanthroline compounds are oxidized. As indicators, the ferrous derivatives of both of the new sulfonic acids give vivid and sharp color changes and, in contrast to the parent ferroin, can b e used in perchloric acid solutions.
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M
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UCH of the inertness of pyridine
toward chemical attack is exhibited by 1,lO-phenanthroline, It can be mononitrated (3) by a fuming nitric and sulfuric acid mixture (in the 5position, on the benzenoid ring), but sulfonation has never been reported. Our success with the sulfonation of 4,7 - diphenyl - 1,lO - phenanthroline (bathophenanthroline) and of 2,g-dimethyl - 4,7 diphenyl - 1 , l O - phenanthroline (bathocuproine) (1) and the interesting properties of the resulting compounds led us to study the sulfonation of the parent material, 1,lO-phenanthroline. By progressively increasing the potency of the sulfonating agent we were finally able to effect the sulfonation. From the sulfonation mixture we have isolated and identified two monosulfonic acids, 5- and 3-. Both of these cyclic iminosulfonic acids react with the ferrous ion but with some interesting variations from the parent ferroin.
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EXPERIMENTAL WORK
Apparatus and Reagents. Spectrophotometric data were secured on a Cary Model 12 recording spectrophotometer and a Beckman Model DU spectrophotometer using 1-cm. matched cells. Measurements of p H were made with a Beckman Model G p H meter. Potential measurements were made with
a Leeds & Northrup No. 7552 potentiometer. The thermobalance used was built in this laboratory. Infrared data were obtained on a Perkin-Elmer Model 21 instrument. 1,lO - Phenanthroline was obtained from the G. Frederick Smith Chemical Co., Columbus, Ohio. 5-Hydroxy-1,lOphenanthroline and 3-chloro-1,lO-phenanthroline were obtained from F. H. Case, Temple University, Philadelphia, Pa. The Amberlite IR-120 used was reagent grade material. All water used was distilled water passed through a monobed ion exchange unit. Sulfonation of 1,lO-Phenanthroline. SEPARATION OF ISOMERS. I n a 3necked, 1-liter, round-bottomed flask, equipped with a water-cooled condenser, mechanical stirrer, and thermometer, were placed 40 grams of 1,lO-phenanthroline monohydrate and 200 grams of ammonium acid sulfate. With stirring, the temperature of the mixture was raised to 365' to 370' C. and held for 10 minutes. The mixture was allowed to cool until solidification was about to occur a t which time the thermometer was removed and 200 ml. of water added cautiously. Concentrated ammonium hydroxide was then added until the solution was basic. The resulting solution was evaporated to dryness. The residue was pulverized and then stirred for 15 minutes with 400 ml. of chloroform. Filtration and distillation of the chloroform left a residue of 3 grams of unreacted 1,10-phenanthroline. The residue of ammonium sulfate and ammonium salt of sulfonation products left from the chloroform extraction was dried and then treated with 4 liters of 85% ethyl alcohol. The mixture was heated to 65" C. with stirring for 30 minutes. While still hot, the mixture was filtered using suction and 500 ml. of water was added to the filtrate. The resulting solution was heated to 65' C. and while hot was passed through a 5 X 20 cm. electrically heated column a t about the same temperature, containing Amberlite IR-120 in the hydrogen form a t a rate of about 300 ml. per minute. The column was then washed with about 500 ml. of hot water. The eluate was evaporated to 135 ml., allowed to stand overnight and the separated solid, a mixture of monosulfonated products, then filtered off. The filtrate, on careful evaporation to dryness, yielded approximately 12 grams of a mixture of various disulfonated and oxidation products. The mixture of monosulfonated products was dissolved in 1 liter of hot water
and the volume of the solution reduced to 400 ml. by evaporation. The mixture was cooled to room temperature and after 2 hours the separated solid was filtered off. Yield: 13 grams of 1 , l O - phenanthroline - 5 - sulfonic acid monohydrate (properties given below). The filtrate was evaporated to 100 ml., cooled to room temperature, and after 2 hours the separated solid filtered off. Yield: 4.5 grams of a mixture of 1,lOphenanthroline-5-sulfonic acid monohydrate and l,lO-phenanthroline-3-sulfonic acid. This mixture was dried and pulverized and then stirred with 300 ml. of methanol for 1 hour. The residue was filtered and recrystallized from hot water. Yield: 1.7 grams of 1,lOphenanthroline-3-sulfonic acid (properties given below). The mixture of disulfonated and oxidation products in the sodium form was dissolved in 50% ethyl alcohol and placed on a column of alumina. A separation was effected using 7070 ethyl alcohol as eluent. Progress down the column was followed by irradiation with ultraviolet light. -is shown by banding and variation in the intensity and color of the fluorescence, five or six components were present. Three compounds were isolated as shown by the infrared spectra of the materials, and these compounds were shown t o be highly soluble in water and to form intense red ferrous derivatives which were unstable when acidified. X o work was done to identify these materials other than to note that the equivalent weight found for a mixture of these compounds agreed well with the theoretical equivalent weight for a disulfonated product.
I,lO-Phenanthroline-5-sulfonic Acid CI~HSN~SOI. H20.
Monohydrate.
Cream colored crystals from water. Melting point: 477-83" C. Displays a yellow fluorescence under ultraviolet light. Analysis (by Huffman Microanalytical Laboratory, Wheatridge, Colo.): found, C 52.16, H 3.60, N 10.43, S 10.20, corresponding t o C11.~H~.~Nz.oSo.9. Equivalent weight found by neutralization (see Figure 5 for titration curve) : 278.0, 277.8; calculated 278.3 [calculated for C12H6N2(S03H)z.HzO, two replaceable hydrogen atoms, 179.21. Loss in weight on thermogravimetric analysis: 1.03 molecules of water over the range 115' to 225' C. Solubility. Water was saturated VOL. 33, NO. 7, JUNE 1961
867
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ing the free acid and evaporating t o dryness. It was difficultto crystallize. It displayed a slight purple fluorescence. Solubility in water a t 25" C.: 7.35 grams per liter. It proved impossible to prepare an ammonium salt of stoichiometric composition. Ferrous Derivative. Prepared from ferrous sulfate, hgdroxylammonium sulfate, and 1,lO-phenanthroline-5-sulfonic acid by mixing and bringing t o p H 5 with sodium acetate. Color: red-orange; see Figure 1 for absorption spectrum; molar extinction coefficient: 12,240 a t 512 mp, the wave length of maximum absorption; Figure 1. Absorption spectra system conforms to Beer's law over the range 0 to 72 p.p.m. of iron. Com1. Ferrous tris(l,lO-phenanthroline-5-sulfonic acid) (9.43 X 10-6M Fe) bining ratio as determined by spec2. Ferrous tris(l,1O-phenanthroline-3-sulfonic trophotometric titration (Figure 2) : acid) (15.1 X 10dM Fe) 1 , l O - phenanthroline - 5 - sulfonic acid: Cary Model 1 2 recording spectrophotometer; iron = 3.06:l. The range of p H over 1 -cm. cells which the ferrous derivative is stable was determined by preparing a series of solutions, each solution containing with 1,lO - phenanthroline-5-sulfonic the same amount of iron, sodium sulfite, acid monohydrate in a constant temand excess of l,lO-phenanthroline-5perature bath a t 25' C. T h e solution was filtered rapidly and aliquots of the sulfonic acid, but varying in p H by tht; addition of hydrochloric acid or filtrate were treated with excess sodium hydro?iide as appropriate. The ferrous iron. The absorbancy of the result is shown in Figure 3. red solutions was measured and comFerrous Tris(1,lO-Phenanthrolinepared with standards similarly pre5-sulfonic Acid) a s an Oxidationpared. Found: 0.518 gram of 1,lOREReduction Indicator. FORMAL phenanthroline-5-sulfonic acid monoD U C T I O ~ POTENTIAL. A solution of hydrate per liter. Proof of Structure. CONVERSION the ferrous derivative of l,lO-pheTO 5 - HYDROXY - 1 , l O - PHENAN- nanthroline was prepared by mixing THROLIKE. 1,lO-Phenanthroline-5-sul- the stoichiometric amounts of ferrous ethylenediammonium sulfate and 1,IOfonic acid monohydrate was fused with phenanthroline-5-sulfonic acid in the sodium hydroxide in a silver crucible, ratio of 1 to 3. A second solution n-as t h e melt dissolved in dilute sulfuric prepared from ferrous perchlorate (preacid, and the free acid neutralized pared by dissolving electrolytic iron in t o pH 7 . The mixture was extracted perchloric acid) and the necessary with isoamyl alcohol, the alcohol layer amount of 1 , l O phenanthroline - 5washed with water, and the alcohol sulfonic acid. evaporated away. The residue was reA standard solution of quadrivalent crystallized from hot ethyl alcohol. cerium was prepared by dissolving The infrared spectrum by the potassium ceric hydroxide in sulfuric acid and adbromide disk technique was identical justing the sulfuric acid concentration with that of 5-hydroxg-1,lO-phenanto 1X. A similar quadrivalent cerium throline [Zacharias and Case (41. solution in 1.M perchloric acid was preSodium and Ammonium Salts. T h e pared. sodium Falt was prepared by neutralizA solution 1M in sulfuric acid was made approximately equimolar in ferrous ethylenediammonium sulfate and the ferrous tris( 1,lO-phenanthroline-bsulfonic acid) (in sulfate solution) and titrated with the sulfatoceric acid solution. A platinum foil and a saturated calomel electrode with agar bridge were used as electrodes. The mid-point of the first part of the titration was taken as the formal reduction potential of the ferric-ferrous system in 1 M sulfuric acid, the mid-point of the second part as the formal reduction Figure 2. Spectrophotometric titraiion potential of the iron-1,IO-phenanthroof ferrous iron with 1,l O-phenanthroline-5-sulfonic acid system. line-5-sulfonic acid -4 similar titration v a s carried out using ferrous perchlorate and 1M perIron: 9.43 X 1 0 moles; 1.1 O-phenanthrolinechloric acid solutions. 5-sulfonic acid: 1.1 5 X 10
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ANALYTICAL CHEMISTRY
0.7 I
Figure 3. 1.
Ferrous acid) 2. Ferrous acid)
p H range of stability tris(1,1O.phenanthroline-5-rulfonis
tris( l,lO-phenanthroline-3-sulfonic
A typical titratfon curve is given in Figure 4. 1,lO Phenanthroline 3 - sulfonic Acid. C12HsS2S03. Cream colored crystals. Melting point, 381" t o 386' C. Displays a yelloiv fluorescence under ultraviolet light. Analysis : Found, C 53.63, H 3.46, N 10.29, S 11.67, corresponding t o C12.2H9 Ji-2 0. Equivalent weight found by neutralization (see Figure 5 for titration curve) : 264.3, 265.8; calculated, 260.3. S o weight loss observed on heating to 250' C. Solubility: 0.92 gram per liter a t 25' C. Proof of Structure. CONVERSION
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TO 3-HYDROXY-1,10-PHENANTHROLINE AND TO 3-CHLORO-1,10-PHENAKTHRO-
1,lO-Phenanthroline-3-sulfonic
LINE.
acid mas fused a i t h potassium hydroxide in a silver crucible, the melt dissolved in dilute sulfuric acid, and the p H brought to 7 . The mixture was extracted with isoamyl alcohol, the alcohol layer washed with water, and the alcohol eyaporated away. The residue was recrystallized from hot ethyl alcohol. The infrared spectrum
f1c
IC
0" 0 9 $08 LQ
07
%06 205 04
0.3
L 5 10 15 I
0
I
I
20
25
I
I
30 35
,
40
Figure 4. Determination of formal reduction potential of iron-1,l O-phenanthroline-5-sulfonic acid system 1 M perchloric acid
NaW-ml. (Curve I)
Figure 5. Titration curves
l2
the di- and polysulfonatea materials takes advantage of their low solubility in water. This low solubility is undoubtedly related to their zwitterion structure. 1,lO-Phenanthroline acts as a monoacidic base, the proton accepted on neutralization presumably filling in the available space between the nitrogen atoms and excluding a second proton. In the 1,lO-phenanthroline monosulfonic acids the transfer of a proton from the sulfonic acid group to the ring nitrogen atoms is apparent from the nature of the titration curves (Figure 5). Because of the low solubility, of the order of 0.003M for saturated solutions, significant data for the curves xere obtained only as the equivalence points were approached. pH was not measured at the mid-points but the breaks and pH values a t the equivalence points were typical of weak acids or protonated amines. The failure to obtain ammonium salts of stoichiometric composition can be explained as (competition of the ring nitrogen atoms and the ammonium ion, that is, the material obtained lvas a mixture of the ammonium salt and the free acid zwitterion. As expected, the combining ratios found for the ferrous ion with the phenanthroline monosulfonic acids, 1:3, were the same as for the parent compound. It is a bit surprising that the differences in the absorption characteristics of the ferrous derivatives are so slight:
1
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1. 1,lO-Phenanthraline 5 -SUIfonic acid (0.501 6 gram) 2. 1,lO-Phenanthroline 3 -SUIfonic acid (0.3293 gram) With 0.1 135N sodium hydroxide Samples completely dissolved at points a and b
4
6
8
NaOH-ml.
was different from that of 5-hydroxy1,lo-phenanthroline and from 4-hy3droxy - 1 , l O - phenanthroline. Hydroxy-1,lO-phenanthroline had not been reported previously. To 0.13 gram of 3-hydroxy-1,lOphenanthroline was added 0.15 gram of phosphorus pentachloride and 0.25 ml. of phosphorus oxychloride. The mixture was heated for 2 hours at 130' C. in an oil bath. The mixture was then cooled and treated with 25 ml. of water. The pH was brought to 7 with sodium hydroside. The solution was extracted with chloroform and the chloroform extracted washed three times with water. The chloroform was evaporated away and the residue taken up in hot benzene. 3-Chloro-1 ,10-phenanthroline was then crystallized from this solution and again recrystallized from benzene. The infrared spectrum of this material was identical with that of an authentic specimen of 3-chloro-1 ,10-phenanthroline (6). Sodium l,lO-Phenanthroline-3-Sulfonate. Prepared by neutralizing the free acid and evaporating. Solubility i n water a t 25' C.: 4.39 grams per liter. An ammonium salt of stoichiometric composition could not be prepared. Ferrous Derivative. SPECTROPHOTOMETRIC PROPERTIES. OXIDATION - REDUCTION CHARACTERISTICS. Prepared from ferrous ethylenediammonium sulfate, hydroxylammonium sulfate, and l,lO-phenanthroline-3sulfonic acid by mixing and bringing t h e pH t o 5 with ammonia and sodium acetate. Color: red-orange: See Figure 1 for absorption spectrum; molar extinction coefficient: 10,840 at 5.7 mp, the wave length of maximum absorption; system conforms to Beer's law over the range 0 to 7 . 2 p.p.m. of iron. Combining ratio as determined by spectrophotometric titration: 1,IOphenanthroline-3-sulfonic acid: iron = 3.15:l. The pH range over which the ferrous derivative is stable was determined as outlined above, see Figure 3. The formal reduction potentials of the iron-l,lO-phenanthroline-3-sulfonic
IO 12 (Curve 2)
16
14
acid system in l M sulfuric acid and in 1M perchloric acid were determined in the manner described above for the 5-sulfonic acid; the results are given in Table I. DISCUSSION AND CONCLUSIONS
That sulfonation of 1,lO-phenanthroline can only be effected by fusion with ammonium acid sulfate at 365' C. attests the extraordinary resistance of 1,lO-phenanthroline to attack. The yields of the various products of sulfonation in this manner are Per Cent 1,l0-Phenanthroline-5-sulfonic acid l,lO-Phenanthroline-3-sulfonic acid Di- and polysulfonated Carbonaceous material and oxidation products Unchanged 1,lO-phenanthroline
30 4 19
39
8
The separation of the ammonium salts of the sulfonation products from ammonium sulfate by their solubility in ethyl alcohol is essentially the same as that employed following the sulfonation of the phenyl-substituted phenanthrolines (1). The subserymt separation of the two monosulionic acids from
Wave Length of
Maximum AbsorphIolar Ferrous tion, Extinction Derivative of M p Coefficient 1.10-Phenanthroline 510 11,100 1;lo-Phenanthroline-5-sulfonic 12,240 512 acid 1,lO-Phenanthroline-3-sulfonic 10,840 517 acid
Table 1. Formal Reduction Potentials of Ferric-Ferrous-1,l O-Phenanthroline-5sulfonic Acid and Ferric-Ferrous-l,lO-Phenanthroline-3-sulfonicAcid Couples in 1M Sulfuric Acid and in 1M Perchloric Acid
Indicator Ferrous l,l0-phenanthroline-5-sulfonicacid Ferrous l,lO-phenanthroline-3-sulfonicacid
Ferrous lI10-phenanthroline-5-sulfonic acid Ferrous 1,10-~henanthro~ine-3-su~fonic acid a
E" on Hydrogen Scale, Volts Potentiometric" Potentiometric" (1M HZSOa) (1M HClOI) 1.16 1.20 1.21 1.23 E on Hydrogen Scale, Volts Visualb Visualb (1M H2SO1) (1M HClOa) 1 26 1 26 (blue, no red remaining) 1 26 1.29 (blue-green, no red remaining)
From mid-point of titration curve. At color change.
VOL. 33, NO. 7, JUNE 1 9 6 1
869
The pH range over which the ferrous derivatives are stable, extends farther into the alkaline range than for the parent 1,lO-phenanthroline, approximately pH 11 in contrast to 9; this may prove of interest in some circumstances. As colorimetric reagents for iron these reagents then have no advantage over 1,lO-phenanthroline in sensitivity, but they do have the definite merit that they can be used in perchlorate solutions. Ferrous tris(1,lOphenanthroline) perchlorate is insoluble and following wet ashing with perchloric acid or the precipitation of protein with perchloric acid, perchloric acid must be removed by evaporation with sulfuric acid before the iron may be de-
termined. This step is not necessary with the new sulfonated reagents. Sulfonation of 1,lO-phenanthroline raises considerably the potential a t which the ferrous derivative is oxidized to the ferric derivative, Table I. As indicators, the ferrous derivatives of both the 5- and 3-sulfonic acid give vivid and sharp color changes. Both are somewhat more sensitive to acid than the parent ferroin, but the 5sulfonic derivative is sufficiently stable to function well as an indicator in strong acids. Both indicators have the advan$age over ferroin that they can be used in perchloric acid solutions. They are ideal for titrations with quadrivalent cerium in either sulfuric or perchloric acid solutions.
A C K N O W LEDGMENl
The authors express their appreciation of grants of chemicals from the G. Frederick Smith Chemical Co., Columbus, Ohio. LITERATURE CITED
(1) Blair, D. E., Diehl, H., Talanfu 7,
163 (1961).
(2) Case, F. H., Catino, S., Scholnick, F.,J. Org. Chem. 19,31 (1954).
(3) Smith, G. F., Cagle, F. W., Jr., Zbid., 12, 781 (1947). (4) Zacharias, D. E., Case, F. H., unpublished work. RECEIVED for review January 3, 1961. Accepted March 6, 1961.
Improved 2-Thenoyltrifluoroacetone Extraction Method for Radiozirconium S. FREDRIC MARSH, WILLIAM J. MAECK, GLENN L. BOOMAN, and JAMES E. REIN Atomic Energy Division, Phillips Petroleum Co., Idaho Falls, Idaho
b An improved method for the determination of radiozirconium, based on the 2-thenoyltrifluoroacetone (TTA) extraction, is described. A fluoride pretreatment converts hydrolytic and colloidal species of zirconium to a form extractable, as the TTA complex, into xylene. Radioiodine, the only fission product significantly extracted with zirconium, is separated in
