REACTION OF NITROGENOXIDE WITH AMINES
April 20, 1961
1319
[CONTRIBUTION FROM THE W. A. NOYESLABORATORY, UNIVERSITY OF ILLINOIS,URBANA, ILLINOIS]
The Reaction of Nitrogen(I1) Oxide with Various Primary and Secondary Amines BY RUSSELL S. DRAGO AND BRUCER. KARSTETTER' RECEIVED AUGUST4, 1960
It was earlier reported t h a t nitric oxide behaves as a Lewis acid toward diethylamine resulting in the formation of Et?NH*+Et*KN20z-. I n order t o establish this as a general reaction type the reaction has been extended t o a whole series of primary and secondary amines. T h e preparation of the adducts, their structure and physical properties are discussed.
Introduction I t has been reported2 that diethylamine reacts with nitric oxide a t -78" to produce a white solid whose formula is Et2NH2+EtzNN202-. Infrared and nuclear magnetic resonance spectroscopy were employed to establish the structure. I t was proposed that in this reaction nitric oxide is behaving as an electron pair acceptor. In order to establish this as a general reaction type for nitric oxide, the initial research has been extended to include a series of amines. Products are obtained of widely varying stability. For example, the methylamine product decomposes spontaneously near - lo", while the di-n-hexylamine product is stable for long periods a t room temperature. Sterically hindered amines do not form products. In this article, the method of preparing the compounds, the physical properties of the compounds and evidence concerning their structure will be presented.
Experimental Purification of Materials.-The amines used in this research are commercially available and can be purified by distillation from anhydrous barium oxide. In most cases the same product is obtained by using the crude amine as t h a t obtained using t h e purified product. Matheson commercial grade nitric oxide is purified by bubbling through 10 M sodium hydroxide and dried by passing through columns of sodium hydroxide pellets. Similar products are obtained when the nitric oxide is used directly without purification in our high pressure experiments. Unless otherwise indicated, the ammonium salt products can be purified by flooding out of a concentrated chloroform solution with ether. Instrumentation.-Infrared spectra were obtained with a Perkin-Elmer model 21 infrared spectrometer with sodium chloride optics. T h e instrument was frequency calibrated using the absorptions of ammonia, carbon dioxide, water vapor and polystyrene. T h e appropriate corrections were applied to the reported spectra. T h e infrared spectra obtained on pertinent compounds are filled with the American Documentation I n s t i t ~ t e . ~ Kuclear magnetic resonance spectra were obtained using a Varian high resolution spectrometer employing a 60 m.c. probe. Saturated, chloroform solutions were prepared in a nitrogen atmosphere and transferred t o dry sample tubes which were flushed with nitrogen. T h e tubes were sealed and stored at -i8" until t h e spectra were run. General Preparative Techniques.-Two general preparative methods, t h e atmospheric pressure and the high pressure method have been employed. T h e same product is ob(1) Abstracted in part from t h e Ph.D. thesis of B. R. Karstetter, University of Illinois, 1960. (2) Russell S. Drago and F. E. Paulik. J . A m . Chem. Soc., 82, 90 (1960). Pertinent references t o other nitric oxide reactions are contained in this article. (3) Material supplementary t o this article has been deposited as Document number 6461 with t h e AD1 Auxiliary Publications Project. Photoduplication Service, Library of Congress, Washington 25, D. C. A copy may be secured by citing the Document Number and by remitting $1.25 for photoprints or $1.25 for 35 mm. microfilm in advance payment by check or money order payable to: Chief, Photoduplication Service. Library of Congress.
tained by both techniques. I n general, higher yields are obtained by t h e high pressure reaction. If the product is unstable it is often more convenient t o use the atmospheric pressure process. In the high pressure method a 200 cc. autoclave is used as the reaction vessel. Sitric oxide is added t o a large 2000 cc. high pressure autoclave which serves as a nitric oxide reservoir and makes it possible t o fill the reaction vessel without opening it directly t o the nitric oxide t a n k . T h e large autoclave is connected to the nitric oxide tank through a valve and t o the reaction vessel through a check valve, a high pressure needle valve and a blowout valve. This assembly is t o insure against a feed back of amine into the nitric oxide tank in the event of an exothermic reaction. T h e reaction vessel is first evacuated, filled with nitrogen and again evacuated. h mixture of equal volumes of amine and diethyl ether is d r a w l into the evacuated reaction vessel containing a glass liner. The reaction vessel is cooled t o - ; S o , the nitric oxide is introduced and after a 24-hour period the autoclave is allowed t o warm t o room temperature. The excess nitric oxide is vented off and the product is removed. Yields vary with the amine-solvent ratio in the range of 60 t o 807,. \Tit11 proper stirring, near quantitative yields can probably be obtained. The yield d a t a reported are not intended t o indicate an upper limit t o be expected. The reaction time variable was not investigated The atmospheric pressure method was described in an earlier publication.* Preparation of Sodium Salt Derivatives.-In our initial report i t was shown t h a t an excess of the diethylammonium salt, dissolved in alcohol reacts with sodium ethoxide t o produce the sodium salt S a + E t 2 X S 2 0 * - . The product is flooded out of solution with ether and washed with chloroform. This reaction has been carried out on many of t h e amine products prepared in this study providing a derivative to aid in establishing the structure of these materials. I n some instances the sodium salts cannot be obtained directly hy this procedure but can be obtained when slight modifications are made. These modifications will be discussed in the section on specific procedures. Diethylamine.-Since our initial report on this reaction,2 we have been able t o increase our yield from the reported 11 t o 63y0 by treating ail ether solution of the amine ( 4 ether t o 1 amine mole ratio) with nitric oxide a t high pressure. U?th agitation or stirring of the reaction mixture nearly quantitative yields may result. The product can be prepared in the pure amine indicating t h a t ether functions only as a solvent for the reaction. Diisopropyl ether and pentane solvents produce the same product without any appreciable difference in yield. T h e yield is very much dependent on the temperature, only a very slight amount of product is obtained when t h e reaction is carried out a t room temperature. Di-n-propylamine.-This product is conveniently prepared by the high pressure technique. The product undergoes a characteristic reaction with hydrochloric acid t o evolve nitric oxide. I t melts with decomposition at 96-97' in a sealed melting point tube and decomposes in a few days a t room temperature. The n.m.r. spectrum of this product is similar t o t h a t of di-n-propylammonium chloride. Elemental analyses are in good agreement with theoretical. Calcd. for [ C H ? ( C H ~ ) ~ ] ~ ~ H Z + [ C HNSS(2C0 2H- :~ ) ? C ], 54.91; H, 11.54; N, 21.35. Found: C , 54.61; H, 11.39; S,21.39. The sodium salt of this compound cannot be prepared by t h e reaction with sodium ethoxide unless the reaction is carried out at low temperatures ( 0 ' ) and under nitrogen. T h e product precipitates from solution upon evaporation of the
RUSSELLS.DRAGO A N D BRUCEKARSTETTER
I s20
solvent under vacuum. The infrared spectra of the sodium salt contains many of the same absorptions as the ammonium
Vol. s3
water. XI1 absorptions attributed to the amiiioiiiuiii ion have disappeared, but the general appearance of the rcst of t h e spectra is similar to t h e ammonium salt. salt but the intense N-H? stretching frequency is absent. Methylamine.-The methylamine product w:~s prepared .lid. Calcd. for S ~ + [ C H ~ ( C H ~ ) ? ] S S I O C,L -39.33; : by the atmospheric pressure method. Aifternitric oxide was H , 7.72; K , 22.94. Found: C , 37.93; H , 7.1i): S , 21.36. passed tlirough the solution for a few hours the solution became deep orange in color and a large amount of solid preDiisopropy1amine.-The reaction between diisopropylacipitated. hfter 22 hr. t h e system was allowed t o warin a n d n i n e and nitric oxide was carried out under atmospheric and the color disappeared. Upon filtration and further warming high pressure conditions. 111both instances the desired prodto near room temperature the white solid instantly decornuct, R2T\;H2+R2SN?02-, was not obtained. Instead, a posed into a cloud of white fumes. So further wark was small amount or white solid (2'.c yield based on amine) predune because of the instability of the product. cipitated. The product melts a t 138-139" and has an elen-Propylamine.-The n-propylamine product is best prcmental analysis in good agreement with diisoprop~-lanipared by the attnosplieric pressure method. I t is slightly tilonium nitrite. Anal. Calcd. for (CH3)?NH?"SOy-: C, 48.61; H , more stable than the methylamine product but too unstable t o obtain tlie infrared spectrum at room temperature or ele10.90; S, 18.90. Found: C , 48.55; H, 10.72; S, 18.71. mental analysis. In order to establish this material as nT h e reported" melting point for the nitrite is 13E-137'. C:~H;SH3+n-C3HiSHS?O?the sodium salt was prepared. Di-n-butylamine.-This product is prepared in 80% yield This is accomplished by carrl-ing out the reaction between by the high pressure technique. It is considerably more sodium ethoxide and the ammonium salt without isolating stable than the di-n-propylamine product and can be stored the ammonium salt. At the end of t h e reaction the system is a t room temperature in the presence of air for several days thoroughly flushed with nitrogen and a solution of sodium before noticeable decomposition occurs. The product is etlioxide in ethauol is added t o t h e cold reaction mixture. insoluble in water and melts in a sealed tube a t 101". The Excess ethoxide is avoided t o siniplify purification. The infrared and nuclear magnetic resonance spectra support its niisture is stirred for 2 hr. under a nitrogen atmosphere, formulation as [CH3(CH?)~]ISH:-[CHP( C H , ) ~ ] ? S X ~ O L - alloved . t o warm t o room temperature and immediately filtered. The product is fairly stable and is purified by washThe t1.m.r. spectra shows the characteristic S H , peak, a peak ing with small purtions of chloroform, ethanol and ether. for the methylene bonded to nitrogen (S-CH?-) and a comElemental analysis and the infrared spectrum 011 the sodium ijlm absorption due t o C H I and the other C H ? groups. salt indicate t h a t tlie n-propylamine reaction is similar t o tlie The alkylammonium chloride spectra 15 similar. secondary amine reactions. A ncd. Calcd. for [CHa(C H ? ) ~ ! I X H ? + [ CC HH ~ (~ ) ?r\;S?:I~ Anal. Calcd. for Na'CH,(CHa)?SHN?O?-: C, 2 5 . 5 3 ; 02-: C, 60.32; H , 12.05; K, 17.58. Found: C , 60.36; H , H , 5.73; S,29.78. Found: C, 24.99; H . 5.46; S,29.33. 11.81; S, 17.24. Isopropylamine.--The isopropylamine product was obDi-sec-butylamine.-This reaction when carried out at vield bl- the high pressure method. I t is high pressure yields a v e r r small amount of material identihie t h m the product obtained ivith n-profied as the alkylammcnium nitrite. pylamiiie. -1sample \vas kept for two days, a t room temCalcd. for CsHlsSH?-SO?C: C, 54.50; H , 11.46; S, perature in a vacuuni desiccator over anhydrous calcium 15.89. Found: C, 54.50; H , 11.48; S,15.51. chloride. The product was purified by washing with ether. The product melts at 108" and has an infrared spectrum I t IS insoluble in chloroform and many other appropri:ite expected for the alkylammonium nitrite. solvents. I t is soluble in alcohol b u t very difficult t o recover Di-n-amylamine.-This product can be prepared by the from this solvent. The product melts with decomposition high pressure technique. I t is very stable; samples have a t 71 O . been stored a t rcorn temperature in air for long periods with.-lnal. Calcd. for (CHl)2CHSH:I-(CH:,)?CHSHS20,-: out noticeable decomposition. The product melts with deC, 40.42; H . 1U.18; S , 31.15. Found: C, 40.29; H , composition a t 101-103". Elemental analysis infrared and l(J.10; S ,31.00. nuclear magnetic resonance spectra are in agreement with The sodium salt n-ai prepared by reacting the isriprt)pylthe formulation of this material as [CHa(CH2)4]?SHa'[CHaammonium salt slurried in ethanol with slightly less than the (CH2)r]yNKvO?-. stoichiometric amount of S a O E t . After stirring for fivc .,lnal. Calcd. for [CH3(CH2)4]rSHI+[CH3(CH?)r] SSzO?-: minutes the product was precipitated by adding ether. The C , 64.12; H , 12.40; S, 14.96. Found: C , 63.82; H , sodium salt n-as thoroughly washed with ethanol and ether. 12.16; N , 15.03. I t is quite stable a t room temperature although some decomDi-n-hexylamine.--The di-n-hexylamine product was positicm was detected after five days. The sodium salt esprepared in 625; yield by the high pressure technique. The plodes in an open melting-point tube a t 122'. purified compound is insoluble in water, stable without A n a l . Calcd. for S a + ( C H a ) n C H S H S i O ? CC, : 25.53; noticeable decomposition for a t least three months and melts H , 5.73; S , 29.78. Found: C , 25.51; H , 5.80; N,29.58. a t 100-11)2". T h e infrared and nuclear magnetic resonance n-Butylamine.-This salt is more stable than that of nspectra have ammonium ion absorptions similar t o the alkylpropylamine but decomposes in a cloud of white fumes after nmmonium chloride. Elemental analysis support the forfour or five minutes a t room temperature. The atmospheric IIIU~LI [CH.j(CH?)i] aSH9'[CHz( CH?'lj]?SS?O?-. pressure method is best suited for ease of preparation. A n a l . Calcd. for [CHS(CH2)jlrSHn-[CHn(CH?)j]?SS1O?-: C, fi6.91; H, 12.66; X, 13.01. Found: C, 67.13; a 4 i ? a / . Calcd. for CH,( CH2).ISH,'CI-I,(CH?).1SI-IS~02-: H , 12.64; K, 12.93. C , 46.56; H, 10.6;: S , 27.16. Found: C, 4,531: H , 10.30; S ,28.23. Piperidine.-The piperidine-nitric oxide compound was prepared in io"/;, yield by the high pressure technique. T h e The sudium salt is prepared without isolating the arnproduct is very soluble in chloroform and somewhat soluble monium salt. I t is purified by washing with alcohol anti i l l ether. I t is best purified by washing the crude material ether. Fairly extensive decomposition of the sodium salt with ether but can be flooded from a chloroform solution was noted within 24 hr. :it room temperature. The product ivith heptane. Its stability is similar t o t h a t of the diethylexplodes in a n open melting-point tube a t 98". amine product. It melts with decomposition a t 69-71'. A n d . Calcd. for Sa-CH:I(CH:!)ISHSyO~C:C, :3O.OS; Ancil. Calcd. for C3HloSH?+CaH~"SS20?-: C, 52.14; H , 6,.51; S, 27.09. Found: C, 30.,58; H, 7.03; S, 27.59. H , 9.ti5; S , 24.3-3. Found: C, 52.01; H , 9.52; S,23.85. 1sobutylamine.--The stability of this atnrnoiiium salt i y Tlie sodiuiii b d t cau best be prepared by a technique decomparable t o the product ohtained with n-butylamine a l l t i icrilxd later in which the intermediate ammonium salt is not isolated. T h e sodium salt is hygroscopic and poor elemental is most conveniently prclxired by the atmospheric pressurc r e r e obtained on the samples prepared. T h e in- method. The sodium salt is made without isolating the i l l rrared spectra indicates conclusively t h a t this is the sodium termediate ammonium salt. The product is filtered unticr nitrogen arid was!ied with chloroform, alcohol and ether. \Lilt, Sa+C;H,"SSiO?-, and t h a t the product contains I t eyplodes in a n open melting-point tube a t 118". -
-
hpril 20, 1961
REACTION OF NITROGEN OXIDE
sec-Butylamine.--So product was obtained by either the high pressure or atmospheric pressure method outlined above. tert-Butylamine .-KO product was obtained by either the high pressure or atmospheric pressure method. A very stnall amount of tert-butylammonium nitrite was obtained. I t melts with decomposition a t 126-127'. Calcd. for (CHa)3CSH3+S02-: C , 39.97; H, 10.08; N, 23.32. Found: C,39.47; H, 9.77; K,22.83. n-Amylamine.-This product has a stability comparable t o t h a t of methylamine and is best prepared by the atmospheric pressure method. When filtered cold, the product disappears in a cloud of white smoke below room temperature. The instability prevented our characterization of the product, but it is assumed t o be similar t o the other amine products. Cyclohexylamine.-The cyclohexylamine product is one of the more stable primary amine products being comparable in stability t o t h a t of isopropylamine. Elemental analysis and infrared spectra were obtained. The product melts with decomposition a t 71-72'. I t is purified by mashing with ether and drying in a vacuum desiccator. Anal. Calcd. for C6HIISH3+C6H11"Klol-: c , 55.77; H , 10.16, S , 21.69. Found: C, 55.91; H , 10.07; S , 20.96. Aniline.-The reaction between aniline and nitric oxide is very exothermic. I n the one instance in our experience, a violent explosion occurred. The heat generated melted the high pressure tubing used in our system.
Discussion The reaction between diethylamine and nitric oxide was reported earlier. This reaction has now been extended to include a whole series of amines, demonstrating that the behavior of nitric oxide as a Lewis acid is a general reaction type. The products obtained for this new series of amines have been established as ammonium salts of the general formula R2NH2+R2NN202- or RNH3+RNHN202- for secondary and primary amines, respectively. Elemental analysis, infrared spectra, nuclear magnetic resonance spectra and the preparation of sodium salt derivatives support the above formulation. Most of the ammonium salts undergo the reaction with sodium ethoxide represented by the general equations RNH3+
or
+ RXHr\;jO2- + X a + + O E t - + K a + + RNHN202- + RXH2 + EtOH
+ R2NK202-
R2NH*+
+ OEt- + + R2NN202- + R2KH + EtOH
-t K a +
Ea+
Elemental analyses of the sodium salt derivative are in good agreement with theoretical. The slight variations reported are due to the difficulty of purification and hygroscopicity of these derivatives. The infrared spectra3 serve to confirm the formulation of these amine-nitric oxide products as ammonium salts. The secondary amine hydrochlorides have strong bands in the 2800-2400
+
cm.-' region arising from the N-H stretch. The
+
NH, deformation appears in the 1600-1550 cm.-' region. The spectra of the products in the regions outlined above indicate the presence of the substituted ammonium ion in the products. In general, the absorptions in the product are shifted to lower frequencies indicating rather extensive hydrogen bonding. In every case these absorptions have disappeared in the sodium salt, although
WITH
XhIINES
1821
the general appearance of the rest of the spectrum is unchanged except for some frequency shifts due to lattice effects and the absence of hydrogen bonding. In the primary amine hydrochlorides there are intense broad bands in the 3200-2800 cm. -l region
+
associated with -NH3 stretching modes. There are bands of medium intensity in the 1610-1550
+
and 1510-1480 cm.-' regions arising from NH3 deformations. The conversion of the primary amine-nitric oxide products to the sodium salts results in the disappearance of the broad band due
+
to -NHy stretching modes. In this region an intense sharp absorption attributed to the 9-H stretching vibration in the anion, RNHN202-, appears. It occurs a t 3253, 3186 and 3lG4 cm.-' in the sodium salts of the n-propylamine, nbutylamine and isobutylamine products, respectively. A careful examination of the infrared spectra of alkyl ammonium chlorides, the alkylaminenitric oxide products and the sodium salts of these products indicates that the N-0 and N-N stretching frequencies occur in the 1215 to 1129 ern.-' region. The N-0 absorptions in the secondary amine.-nitric oxide addition compounds occur a t lower frequencies than those in the primary amine compounds. The more basic secondary amines would be expected to feed more electron density into the system and increase the single bond character of the N - 0 bond. The nuclear magnetic resonance spectra of the nitric oxide products of di-n-propylamine, din-butylamine, di-n-amylamine and di-n-hexylamine have been obtained and compared with the spectra of the corresponding amine hydrochlorides. A11 of the spectra were obtained on saturated chloroform solutions of the compounds. The n.m.r. spectra serve as confirmatory evidence for the structures proposed and are consistent with the spectrum of the diethylamine compound. The N-H resonance in the nitric oxide products and the amine hydrochlorides occurs a t lower fields than the solvent chloroform peak. This eliminates structui es which place hydrogens on the oxygen for they would occur a t highe1 fields. The next peak observed in the spectra is a t higher field strength than the chloroform peak and is due to the >N-CHz- protons. The other -CH2- resonances overlap the -CH3 resonance 2nd give rise to a complex absorption a t higher fields. The above evidence is all in support of our postulate that the products of the nitric oxide reaction with primary and secondary amines are best formulated a s animonium salts of the general formula &",+R2NN202- and RNHBfRNHN202-. Several of the amines studied, sec-butylamine, tert-butylamine, diisopropylamine and di-sec-butylamine do not form addition compounds under the conditions of our experiment. I t has been demonstrate@ that these amines undergo a pronounced steric interaction with the reference acid trimethyl(5) H. C. Brown and H. Pearsall, J. A m . C h e m . SOC.,67, 1705 (1918); H. C. Brown, M. D. Taylor and Sei Sujishi, ibid., 73, 2404 (1931); H . C . Brown and G. K . Barbaras, ibid., 7 6 , G (1953).
D. L. CASON AND H. 11. NEUMANN
1822
boron. I t is proposed that a similar steric interaction toward the N202 group prevents the formation of stable adducts with these amines. Small amounts of the alkyl ammonium nitrites are obtained instead. Some definite trends in the stability of the aminenitric oxide products have been noted. The ammonium salts of the straight chain primary amines show a stepwise increase in stability from methylamine through n-butylamine. The n-amylarnine product is comparable in stability to that of methylamine. Isopropylamine and cyclohexylamine form compounds which are more stable than those of the straight chain primary amines. The stability difference of the sec-butylamine and isopropylamine product is surprising. The nitric oxide products of symmetrical, straight chain secondary amines exhibit a steady increase in stability from the diethylamine through the di-n-hexylamine products ; relatively, the latter two members of the series are very stable. Two branched-chain analogs, diisopropylamine and di[COA’TRIBUTIOX FROM
THE SCHOOL O F
Yol. 53
sec-butylamine do not form product but give very low yields of the alkylammonium nitrites. These observations on “stabilities” are purely qualitative and are based upon visual observation of the ease of decomposition of the material. I t has not been possible to correlate all of the “stabilities” described above with any single property of the amine donor. The basicity of the amine, crystal lattice effects, steric effects and volatility of the amine are all important considerations. With few exceptions, the stability of the products parallel the basicity of the amines as measured by the heat of formation of the triinethylboron adducts. There are some exceptions to this general :ule in instances where one or more of the above factors become controlling. Acknowledgments.-The authors would like to express their thanks to the Department of the Army Ordnance Corps for the financial support of the research under Contract KO. DX-11-022-ORD 2772.
CHEMISTRY, GEORGIA IXSTITUTE
OF
TECHNOLOGY, ATLANTA, GEORGIA]
Stability of the Chloro-complexes of Iodine in Aqueous Solution1 BY D. L. CASONAND H. AT. KEUMAKN~ RECEIVED ACGLXT26, 1960 Spectrophotometric measurements have been used t o study the stability in aqueous solution of the chloro-complexes of iodine in the (O), ( I ) and (111) oxidation states. The ion 12C1- is characterized by absorption maxima a t 248 and 437 mG, Qualitative observations were made on t h e conditions necessirj- for disproportionation of 12C1- t o I- and IC12- and for the air oxidation of IzC1- t o IC12-. T h e dissociation constant for IyC1- was determined bh- a spectrophotometric method, and the value so obtained was compared with t h e varietJ- of values in the literature. T h e most probable value is 0.60. The ion IC12- is characterized by absorption maxima a t 224 and 313 nip, and the spectral d a t a on its dissociation are consistent with the work of Faull. Spectral evidence for IC1,- could not be found, either in solutions prepared from IC1, or from KI, K I 0 3and HCl. Solutions equivalent t o iodine (111) in terms of oxidation were found to be equimolar mixtures of ICln- and Io3-.
The existence of chloro-complexes of iodine in dissolve salts. I t was then thoroughly dried and purified by the (0), (I) and (111) oxidation states has been sublimation. Iodine monochloride mas made by treating the purified well established. However, there are a number of iodine with condensed chlorine according t o the method of conflicting statements in the literature as to the Cornog and Karges.4 I t was purified by two or three restability of these complexes in aqueous solution. crystallizations. .4 modification of the method of Booth and RIorris5 was The purpose of this work is to determine the condiused for t h e preparation of iodine trichloride. Sinall tions under which these complexes exist in aqueous amounts of liquid IC1 were added, a drop or two a t a time, solution. I t was hoped that this evidence would t o condensed chlorine. After all the IC1 was added, most of aid in interpreting the behavior of astatine in the excess chlorine was allowed t o evaporate froin the solid chloride solutions. Evidence for the existence of IC1,. IVhen solutions of IC13 were desired some IC1, would be shaken out onto a piece of paper, allowed a chloro-complex of astatine has been p r e ~ e n t e d , ~tcrystals o stand for a few seconds to let the excess CI? escape and but i t has been difficult to make arguments about then added t o the solvent without further delay. the oxidation state without further information d l l other chemicals were commercial materials of reagent grade. The concentrations of stock solutions were deterabout the behavior of iodine. The work reported here has established the nature mined by the standard iodometric method. Spectral Measurements.-The absorption spectra were and amount of the iodine species in chloride solu- determined with either a Beckman Model DU spectrophotions where the iodine concentration is in the range tometer or a Beckman Model DE(-1 spectrophotometer. lov5 to M . In addition to the experimental Most of the measurements were made with matched, fused work, which has principally involved spectrophoto- silica cells having a light path of 1.000 =k 0.003 cni. -4 water jacket was used t o keep the cells at a constant ternmetric measurements, the earlier data in the liter- perature of 25.0 & 0.5’. Even though the cells were ature has been evaluated. cleaned repeatedly, fluctuations in readings occasiorially appeared due t o impurities in the cells. This difficulty with Experimental iodine solutions has been observed and discussed by other Materials.--;\ sample of commercial iodine was ground into powder arid treated with successive portions of w‘iter t o
workers.6
(1) Taken in part from a thesis submitted by Dennis Lamar Cason in partial fulfillment of t h e requirements f or t h e M S. degree, June 1959. (2) Requests for reprints should be addressed t o this author. (3) H. M. Xeumann, J . Inorg. Xuclear C h e m . , 4, 349 (1987).
(4) J. Cornog and R . A. Karges, “Inorganic Syntheses,” Vol. I , XlcGraw-Hill Book Co., S e w York, N. Y . , 1939, p. 165. ( 5 ) H. S. Booth and W. C. Morris, ibid., p . 167. (6) J. H.Wolfenden, Anal. Chein., 29, 1098 (1957).
