other types as well. In this event, 6 for a given ligand type may be used to predict chelate stabilities for the metals between Mn and Zn. LITERATURE CITED
(1) Albert, A., Barlin, G. B., J . Chem. SOC.1959,2384.
(2) Badger, G. M., Buttery, R. G., Ibid., 1956,3236. (3) Burger, K., Talanta 8, 769 (1961). (4) Charles, R. G., Freiser, H., J. Anz. Chem. Soc. 74, 1385 (1952). (5) Cheney, G. E., Freiser, H., Fernando, Q., Ibid., 81, 2611 (1959). (6) Edinger, A., Ber. 41, 938 (1908).
(7) Fernando, Q., Freiser, H., J. Am. Chem. SOC.80, 4928 (1958). (8) Freiser H., Charles, R. G., Johnston, W. D., Zbid., 74, 1383 (1952). (9) Freker, H., Fernando, Q., Cheney, G. E., J. Phys. Chem. 63, 250 (1959). (10) Freiser, H., Lee, H., J. Org. Chent. 25. 1277 11960). (ll)'Johnstdn,- W. D., Freiser, H., J. Am. Chem. Soc. 74, 5239 (1952). (12) Kuznetsov, V. I., Bankovskii, Iu. . A., Ievin'sh,. A. F.; J. Anal. Chent. USSR 13, 299 (1958). (13) Lee, H. S., M. Sc. thesis, Department of Chemistry, University of Arizona, Tucson, Ariz., 1960. (14) Leussing, D. L., Inorg. Chem. 2, 77 (1963).
(15) Leussing, D. L., J . Am. Chern. SOC. 80, 4180 (1958). (16) Leussing, D. L., Talanta 4, 264 (1960). (17) Ponci, R., ,Gialdi, F., I1 Farmaco Pavza, Ed. Scz. 9, 459 (1954); C. A . 49, 11657b (1955). (18) Taylor J. R., Virginia J. Sci. 3, 289 (1943). RECEIVEDfor review March 7, 1963. Accepted May 31, 1963. Sixteenth Annual Summer Symposium, Division of Analytical Chemistry and ANALYTICAL CHEMISTRY,Tucson, Ariz., June 1963. The authors gratefully acknowledge financial assistance from the U. S. Atomic Energy Commission.
Characterization of Iodobenzene and Its Homologs by Formation of Polyvalent Iodine Derivatives with Peracetic Acid JACOB G. SHAREFKIN and HAROLD SALTZMAN' Brooklyn College of the City University, Brooklyn, 70, N. Y. Iodine-substituted benzenes have been characterized b y reaction with commercial 40% peracetic acid to form iodobenzene diacetates and iodoxy compounds. The diacetates were readily hydrolyzed to iodoso compounds. All three types were identified by their melting or explosion points and their quantitative reaction with iodide to form iodine, which was titrated with standard thiosulfate. Formation of these polyvalent iodine compounds was difficult with compounds having strong electron-attracting substituents which reduce reactivity, and was also difficult with strongly electron-releasing groups that cause ring oxidation.
I
aryl iodo compounds may be effected b y electrophilic ring substitution to either bromo, nitro, or sulfonamide derivatives (4). These may be difficult t o purify because of polysubstitution or formation of isomers, and they are not used when there is a n alkyl substituent on the ring that can be oxidized t o the corresponding iodobenzoic acid. A more suitable derivative should be obtained from a reaction involving the iodine atom at its site on the ring and Grignard reagents prepared from aryl halides and reacted with isocyanates t o form anilides (IS). Because of the sluggish formation of aryl Grignards, these derivatives have not been used extensively. One method utilizing the 1 Present address, Department of Cheinistry, New York University, Washington Square, N. Y. DENTIFICATION OF
1428
ANALYTICAL CHEMISTRY
aryl iodine atom is based on its reaction with elementary chlorine t o form iodosodichlorides, but these adducts are stable for only a few hours (9). A rapid qualitative test for aromatic iodine compounds (14) suggested the extension of the formation of iodobenzene diacetates (9, 11, 12, 18) with commercial, 40% peracetic acid to both characterization and analysis of iodinesubstituted benzenes. The diacetates formed were ArI CHaCOOOH CHaCOOH ArI(OOCCH& H20
-
+
+
+
stable, readily purified, and had definite melting points. They also oxidized iodide ion quantitatively so that thiosulfate titration could be used to determine the molecular weight. ArI(OOCCH& 2HI ArI I p 2CHaCOOH
+
-
+ +
The iodobenzene diacetates were readily hydrolyzed by aqueous alkali to the corresponding iodosobenzenes (16). These iodoso benzenes were identified b y their melting points and their molecular weights, as determined b y thiosulfate titration of iodine liberated from iodide. ArI(O0CCHa)z 2NaOH ArIO 2CH8COONa ArIO 2HI +. ArI 1% HzO
+
+
-
+ + +
More vigorous conditions than those for the diacetate preparation gave aryl iodosy compounds ( 1 7 ) ,which had definite melting points and quantitatively liberated twice as many equivalents of iodine from iodide as the diacetatcs and iodoso compounds. The aryl iodoxy
compounds could similarly be used for characterization. ArIOz
+ 4HI
+ .
ArI
+ 212 + 2Hz0
The data for polyvalent iodine compounds prepared from 10 iodo substituted benzenes are summarized in Table I. A number of aryl iodobenzene dichlorides were prepared by reaction of the iodobenzenes with a mixture of 40% commercial peracetic acid and hydrochloric acid. This proved to be more convenient than the addition of elementary chlorine (9). EXPERIMENTAL
Reagents and Solutions. Aryl Iodo
Compounds. All iodine-substituted benzenes were Eastman grade. 40'% Peracetic Acid. The composition of the regular commercial grade has been described (14). Standard Sodium Thiosulfate Solution. A 0.1N sodium thiosulfate solution was prepared by dissolving 25 grams of Baker and Adamson ACS reagent grade T\TazS20a. 5Hz0 in 25 ml. of distilled water and diluting to 1000 ml. in a volumetric flask. This solution was standardized by the method of Treadwell (16) using Baker and Adamson ACS reagent grade POtassium iodide and Baker and Adamson ACS reagent grade resublimed iodine. Procedures. Peroxide Content of Peracetic Acid. T h e specifications for t h e 407, commercial peracetic acid indicate t h a t 100 grams should contain 41.3 grams of peracetic acid and 5.1 grams of hydrogen peroxide, so t h a t the total peroxide content should be 0.69 mole or 1.38 equivalents per 100 grams. This must be determined
Table 1.
Melting Points, Molecular Weights, and Percentage Yields of Polyvalent Iodine Compounds Prepared from lodobenzenes
Yield, yo 86
Iodo compound Iodobenzene o-Iodotoluene
86
m-Iodotoluene
83
p-Iodotoluene
73
2-Iodo-m-xylene
88
2-Iodo-p-xylene
65
4-Iodo-m-xylene
76
o-Iodophenetole
77
4-Iodobiphenyl
51
o-Iodobenzoic acid Abbreviations:
c
E
=
Diacetate M.W. E322 32lC E336 336c E332 336" E329 336" E350 350c E342 35OC E351 350" E366 36GC E395 398C
axperimental valuc; L
M.P.
El59 L158 E138 L130-2 El56 Ll54 E110
L104 E31:
E153 Lira
Yield, yo 90 84
85 83 90 68
E128 L128
78
E118
41
b
31 97
=
E240
L234 E242 L234 E249 L248 E265 L248 E255 1,248 -~ E280 L264 E311 L296 E262 L264
--___
M.P.
yield, %
E210 L210 E184 L178 E178 L180-5 E179-83 L175-8 El69
74 41
93 78 68
b
E159
58
E97b
55
E68-71
43
I3208
51
1,200
~~
b
El40
Iodoso M.W. E22 1 L220 E264 L234
b
6
E234 L233
Iodoxy M.W. E236 L236 E254 L250 E251
L2.50 E249 L250 E268 L?64
E279
L264 E268 L264 E278 L2S0 E334 L312
M.P.5
E230 L227 E208 L210 E208 L214 E208 L228 E1F7 E173 Lli8 E195 L193 E167 b
literature value
Explosion point. S o t reported. Calculated value.
periodically, for t h e peroxide strength falls off on long standing and if t h e reagent is contaminated. Peracetic acid is not effective for t h e reactions described below a t concentrations less t h a n 1.0 equivalent of total peroxide per 100 grams of solution. The following modification of the method of Treadwell (16) and Kingzett (6) was used to determine total peroxide. About 0.5 ml. of the peracetic acid was added to 51 weighing bottle, the stopper inserted, and the sample weighed. This bottle was opened as it was dropped into a 500-ml. Erlenmeyer flask containing 100 ml. of 30Oj, HzS04 and 20 ml. of 20% KI solution. The contents of the flask were mixed, the flask stoppered ind stored in the dark for 15 minutes, and then the contents titrated with the standard thiosulfate using starch 51,s indicator. Determination of Molecular Keights of Iododiacetates, Iodoso, and Iodoxy Compounds. The method of hlasson (8) and Lucas ( 7 ) for iodosobenzenes and iodoxybenzenes was applied to the diacetates and dichlorides. To a 250-ml. iodine flask, there was added 100 ml. of distilled water, 10 ml. of 30% sulfuric acid, about 2.0 grams of potassium iodide, and 10 ml. of chloroform. The lip of the flask was carefully dried arid a finely-ground, weighed sample of about 0.5 gram Fras added. The flask was stoppered and shaken continuously for a period of 15 minutes. The contents were titrated with standard thiosulfate solution t o a yellow color, starch solution was added, and the titration continued t o the end point discharge of tlit blue color. Prrpnratioii and I'rirification of Polyvalent Iodine Compclunds for Cliarncterization. Both a Tenera1 technique and several examples are given for the
preparation and purification of the aromatic polyvalent iodine compounds. These are readily adapted to the semimicro scale, using 0.5-gram samples of iodo compounds, inasmuch as the yields after purification were sufficient for both melting point and molecular weight determinations. General Procedure for Diacetate Preparation. T h e iodo compound (0.04 mole) was placed in a 50-ml. Erlenmeyer flask fitted with a magnetic stirrer which was placed in a beaker of water. A slurry with acetic acid was prepared with those iodo compounds t h a t are solid. T o this was added, by means of a dropping funnel, about 13 ml. of peracetic acid over a period of 15 minutes while the water bath was maintained at about 30" C. After addition was complete, stirring was continued until a homogeneous yellow solution formed and crystallization of the diacetate began. The mixture was then diluted with water and cooled in a n ice bath. It was filtered and the solid was washed and macerated on the filter paper, first with cold water and then with petroleum ether after it was dry. TT7here no crystallization could be induced, the homogeneous solution was extracted with two small portions of chloroform after dilution with water. The chloroform extract was evaporated to 5 to 10 ml. and the remaining solid filtered off. After filtration, the clear chloroform solution was diluted with petroleum ether and the solid diacetate was filtered and dried. T o 5.72 grams of o-iodotoluene was added 13 ml. of peracetic acid over :I 20-mi~irite period, M ith tlir hat11 temperature maintained at YO O c'. After addition was completed, stirring was continued for 1 hour during which
the original two layers disappeared. A homogeneous yellow solution was farmed and the reaction mixture soon solidified. The reaction mixture was diluted with 30 ml. of water and filtered, and 50 ml. of water was used to wash and macerate the diacetate on the filter paper. The dry crystals were then washed and macerated with 50 ml. of petroleum ether on the filter paper. The yield of fine white crystals was 11.60 grams or 86% of theoretical. This material melted a t 128-9" C. (lit.: 130-2" C.) ( I O ) . Recrystallization from 41u acetic acid gave fine white crystals which melted at 138" C. 2-Iodo-m-xylene Diacetate. T o 9.28 grams of the iodo compound was added 13 ml. of peracetic acid over a 20minute period, with the water bath at 30" C. After about 75 minutes, a clear yellow solution formed and crystallization began. The mixture was transferred to a small beaker with 50 ml. of water and cooled in an ice bath. Lumps that formed were broken u p against the sides of the beaker. The mixture was then filtered and dried to give a yield of fine white crystals weighing 12.27 grams or 88% of theoretical. This product melted at 145-7" C. while that obtained by crystallization from 5M acetic acid melted at 153" C. This compound was not previously described in the literature. o-Iodosobenzoic Acid. The normal procedure gave stable o-iodosobenzoic acid instead of the expected diacetate. This substance has been described as a cyclic iodoso compound by the early German workers ( 1 ) and more recently by Keefer and A n d r e w (6). A slurry n a s made of 9.22 grams of o-iotlolmizoic* acid and 12 ml. (Jf acetic acid. T o this slurry was added 14 ml. of peracetic acid over a 20-minute VOL. 35, NO. 10, SEPTEMBER 1963
0
1429
period, keeping the temperature of the bath at 30" C. With the initial addition, a red color was observed and the solid did not entirely go into solution. Nor did the characteristic yellow color of diacetate formation appear. After addition, the flask was allowed t o stand for 25 minutes a t 30" C. with no stirring. The mixture was then transferred t o a small beaker with 50 ml. of water, cooled, and broken up with a spatula. The slightly-pink solid a as filtered and washed with 150 ml. of water. After drying, i t weighed 10.24 grams (97y0 yield) and melted at 234" C. (lit.: 209-lo", 226", 233" C.). Recrystallization from 5 N acetic acid yielded fine white needles melting sharply at 234" C. General Procedure for Iodoso Compound Preparation. T h e diacetate (0.01 mole) was finely ground in a mortar a n d t o i t mas added, with vigorous grinding, about 10 t o 20 ml. of sodium hydroxide solution ranging from 3 t o 6-V. T h e first portion of base added was small and was especially well-ground with the diacetate. After addition was completed in 5 minutes, the mixture was allowed to stand at room temperature for a period of time which depended on the individual compound. Occasionally, the mixture was ground during this time. It was then diluted with about 50 ml. of water and filtered on a Buchner funnel. It was macerated on the filter paper, washed with a n additional amount of mater to free it from alkali, and the dry solid ground with about 25 to 100 ml. of chloroform and filtered. The purity of the products was determined by titrating for molecular weight as described b y Lucas (7). As with the iodoxy compound titrations, the solid was finely ground before being weighed out. m-Iodosotoluene. The m-iodotoluene diacetate titrated to show a molecular weight of 332 (theoretical = 336). T o 3.36 grams of this finely-ground diacetate in a mortar was added 17 ml. of 3N XaOH. This was allowed to stand with occasional grinding for 30 minutes, and the mixture was diluted with 30 ml. of water. The yield of dry yellow amorphous powder was 2.00 grams or 85% of theoretical. It melted over a wide range, 178-84" C. (lit.: 180-5" C.), and titration showed a molecular weight of 240 (theoretical = 234). 2-Iodoso-p-xylene. The data from 2-iodo-p-xylene diacetate titration gave a molecular weight of 341 (theoretical = 350). To 3.50 grams of this finelyground diacetate in a mortar was added 17 ml. of 3N NaOH. This was allowed to stand for 30 minutes with occasional grinding and then diluted with 25 ml. of water and filtered. The product was washed with 30 ml. of water on the filter paper. The yield of amorphous yellow powder, which melted a t 15960" C. (lit.: ca. 200" C.) was 1.69 grams or 68% of the theoretical. Titration data showed molecular weight of 265 (theoretical = 248). KOchloroform wash was used here inasmuch as i t resulted in formation of a gel. 1430
ANALYTICAL CHEMISTRY
General Procedure for the Preparation of the Iodoxy Compounds. I n a 50-ml. Erlenmeyer flask, equipped with a magnetic stirrer and inserted into a beaker of water, was placed 0.02 mole of iodo compound. Solid iodo compounds were slurried with acetic acid. To t h e slurry \vas added about 13 nil. of peracetic acid from a dropping funnel over a period of about 16 minutes. T h e water in t h e b a t h was maintained at about 30" C. After addition, the reaction mixture was stirred until the solution turned yellow. The solution was then transferred with hot nater to a 125-ml. Erlenmeyer flask, which was attached to a reflux condenser and inserted in an oil bath. Some boiling chips nere placed in the flask and the mixture was s l o ~ l yheated to prevent foaming. A temperature of 105" to 110" C. wa5 maintained for a period of time which depended on the individual iodo compound. Sercral of the iodo compounds required an additional amount of peracetic acid, n hich was added to the cooled flask. The cooled flask was reheated slomly to prevent excess foaming. The reaction mixture was then cooled, filtered (some additional yield may be obtained by careful evaporation of the filtrate to small volume), and the dry solid macerated with chloroform to remove unreacted diacetate and iodo compound. The molecular weights of the iodoxy compounds were determined by titration and used t o determine their purity. Two of the iodo compounds did not yield the iodoxy compound by direct oxidation and their iodoxy compounds were readily prepared by disporportionation of the corresponding diacetates. p-Iodoxytoluene. Over a 15-minute period, 13 ml. of peracetic acid nere added to a slurry of 4.36 grams of piodotoluene and about 1 ml. of acetic acid. The water bath \$-ab maintained a t 30" C. The mixture was allorved to stir for an additional 15 minutes and the yellow solution was transferred to a 125-ml. flask with 25 ml. of warm water. This flask was slowly heated under reflux to 105" C. in an oil bath. When foaming occurred, i t was necessary to cool the flask momentarily to break u p the foam. The heating was maintained for 15 minutes and the contents of the flask then cooled and filtered. The dry p-iodoxytoluene was macerated with 25 nil. of chloroform to give a yield of fine nhite ponder, which mas 3.90 grams or 78% of theory. This material exploded in a capillary tube at 208" C. (lit.: 228" C.) ( I O ) and its titration 11ith thiwulfate gave a molecular weight of 249 (theoretical = 250). 4-Iodoxy-m-xylene. To 4.64 grams of Piodo-m-xylene n a s added 14 ml. of peracetic acid over a 15-minute period, The temperatu:e of the bath was maintained a t 30 C. and the yellow solution that formed 1%-asstirred a t this temperature for 15 minutes This solution was then transferred to a reflux apparatus with 30 ml. of hot water, slomly heated under reflux to 105" C., and kept at this temperature for 25 minutes. The fla.k was then
cooled, the product ivab filtered, and the dried 4-iodoxy-m-xylene was macerated with 40 nil. of chloroform and filtered. The mhite amorphous powder weighed 2.90 grams or 55% of the theoretical and exploded very sharply in a capillary at 195°C. (lit.: 193" C.) ( 3 ) . Titration of this compound gave a molecular weight of 268 (theoretical = 264). General Procedure for the Preparation of the Dichlorides. Eight milliliters of peracetic acid were added dropwise to a 50-ml. Erlenmeyer flask which contained a mixture of 0.02 mole of iodo compound and 2 ml. of concentrated hydrochloric acid. T h e reaction was carried out a t room temperature and the addition time was 5 minutes. During the addition, T igorous stirring was maintained by means of a magnetic rtirrer. After an additional 5 minute> of stirring, the product n a. filtered and na-hed n itli 20 nil. of n-ater. The dry solid \vas naqhed n i t h 20 nil. of petroleum ether. The purity of the product n as similarljdetermined by titration and calculation of the molecular weight. Iodobenzene dichloride. The procedure described above gave a yield of 2.47 grams of bright yellow crystals or 45y0 of the theoretical, and its titration showed a molecular n eight of 274 (theoretical 274). After about two weeks, the dichloride changed to a brown oil evolving hydrogen chloride. DISCUSSION
Aryl iodobenzene diacetate and its homologs were formed by using 2.5 moles of 40% commercial grade peracetic acid to oxidize 1 mole of the iodo compound. The peracetic acid lvas sufficiently stable to give rapid reaction and good yields even after standing for 1 year but not when the peroxide content Lad decrea3ed by 25%. Iodobenzene yielded 867, of a product whose analysis showed 99.5% iodoso benzene diacetate. Important factors in preparing the diacetates were temperature control a t about 30" C. and slow addition of the midant to the iodo compound. Reaction temperatures above 30" C. or too rapid addition of peracetic acid to a liquid iodo compound or a slurry of solid iodo comliound in acetic acid produced iodoxy compounds rather than diacetates. The nature of ring substituents plays an important role in the preparation of aryl iodoso diacetates. Strongly electron-attracting groups, such as the nitro, inhibit the oxidation of aryl iodo compounds under these conditions while electron-releasing groups cauqe vigorouk ring oxidation and diacetates were not isolated. Best yields mere obtained with iodo compoundg whoae subtituents groups had intermediate electronic effect.. The diacetates were readily hydrolyzed to the corresponding iodoao compound M hen reacted with aqueous alkali. Methods in the literature
employ the iodoso dichlorides, which arc unstable and must be prepared immediately before hydrolysis. Diacetate hydrolysis gave a 9096 yield of iodoqobenzene, which was found by titration t o be 99.5% pure. Both the yield and purity compared fa1 orably n ith those in the literature forth: hydrolysis of the dichloride. The diacetates a ere macerated n i t h sodium hydroxide d u t i o n and the iodoso compounds 11ere filtered off and purified b y wishing Y ith chloroform to remove the unreacted diacetate. Iodoxybenzenes w r e formed from iotlobenzene and it5 hoinologs n hen inore vigorou. conditions were used than those for diacctatc preparation. Twice the, amount of o d a n t , or 5 moles of Iicro\itlcl pc'r mole oj iodo compountl. n as ubetl. After addii ion n ab complete, a t w T$ a' added to thi. reaction mixture, nhicli nab then rcfluxed for about 45 minutes. The niixturz ivas then cooled, thc iodoxy compound removed by filtration, and the solid washed TT ith chloroform to extract unreacted iodo compound or diacehte. With iodobenzene, the J ield of iodo\ybenzene was i 4 % and the compcsition was determined by titration to he 100%. Iodo compounds that did not react n ith iieraccxtic acid to forn- iodo.0 diacetate because of their electron attracting substituents al-o failcd to form iodoxy derivatives.
Anornalous cases Ivere 2-iodo-mxylene and o-iodophenetole, which did not yield iodoxy compounds when subjected to normal oxidation conditions. Their diacetates mere used in disproportionation reactions which gave the iodo and iodoxy derivatives. This was a new application for iodoso diacetates inasmuch as disproportionations reactions cited in the literature used only the iodosobenaenes (16). A number of aryl iodoso dichlorides were prepared with a mixture of 40% peracetic acid and hydrochloric acid. Khile the yields were not high, the purity of the products compared favorably with those in the literature. Reaction mas presumed to occur either by in situ oxidation to chlorine which reacts with the iodo compound or by formation of iodoso compound that reacts with hydrochloric acid. The procedure was also adapted to the small scale preparation of iodobe dichloridet h a t are used in qualitative organic analysis for identification of aryl iodo compounds. Of the three isomeric iodobenzoic acids, only o-iodobenaoic acid underwent oxidation with 40% peracetic acid. However, the product mas not a diacetate but rather a stable, cyclic iodoso compound which resisted the vigorous conditions ubed for iodosy formation and alio failed to undergo disproportionation when heated under reflux.
LITERATURE CITED
(1) Askenasy, P., Meyer, V., Uer. 33, 534
(1900). (2) Boeseken, J., Schneider, G., .T. Prakt. Chem. 131,285 (1931). (3) Datta, R. L., Ghoudhurry, J. K.,
J . A m . Chenz. SOC.38, 1085 (1916). (4) Huntress, E. H., Carten, F. II.,Ibid., 62, 511 (1940). ( 5 ) lieefer, R. M., Andrews, L. J., Ibid., 81, 2374 (1959). (6) Kingzett, C. T., J . Chem. SOC. 37, 802 (1880). 171 Luctas. H. .I . Iiennedv. E. R.. Formo. N. IT.,Orq. Sin. 22, 69"('1942). ' (8) Masson, I., Race, E., Poundcr, F. E., J . Chem. SOC.1935, 1669. ( 9 ) Sichol, J. C., Sandin, R. B., J. Am. Chem. SOC.67, 1307 (1'345). (10) Ortoleva, G., Gam. Chim. Ittd. 30 11, \
I
-
I . ilnonl. \----, (11) Pausacker, IC. H., J . Chem. SOC. 1953, 1989. -1
(12) Pausacker, E;. H., Scroggic., J. G.,
Ibzd., 1954, 449'3. 113) Scliwartz. A. 31.. Johnson. J. I > Kcl) is large, (on the order of 10-3 t o lop4), the addition of Bu4SBr will increase the acidity of a solution of HX relative to that of a dilute base solution since Reaction 2 is driven to the left t o a greater extent than Reaction 1. Direct cornparibon of the dissociation constants of tetrabutylammonium hydroxide and tetrabutylammonium salts could not be made, owing t o unreliable VOL. 35, NO. 10, SEPTEMBER 1963
0
1431
