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The acid dissociation constants of 2,3-quinoxalinedithiol
Analytical data
1240
Etbd-On a etFectu6 du Ltudcs potentiom&ique et de solubilit6 d@ fcrroqwluru de nickel, cobalt. mallxall&8c(lI) et cadmium toutea
REFERENCES 1. A. Bellomo. T&n&, 1970.17,1109. 2. A. Bellomo, D. De Marco and A. CaJak. Proc. 2nd Conf. Appl. Phy. Gem. 4th Symp. Oscillometry, vazpcem, Hungary, 1971. 3. K. L. Cbang. Anal. Chem., 1955.23.1594,. 4. G. Jander and H. W&t, Lehrbuch dcr amalyttichen undpr&watioen uno~chen Chemie, Hiczl v&g, stuttgart, 19s9. 5. W. Pmndtl, 2. Anorg A&em. Chem. 1932,208,420. 6. I. V. Tananaev and M. A. Cluskova, Zh. Prikl. m., 1959,32,1899. 7. I. M. Koltoff and A. plcuson, Znd. Gem., Anal. Ed., 1945,4,171. 8. E. L. Nima, R. E. Hamm and G. L. ?ec ’ , Anal. Chem. 1950,22,970. 9. D. F. Swinehart, ibti., 19Sl,23,381. 10. J. S. Bcshmukb and M. Vmucopakm, J. ZndlrmChm. Sot., 1957,33,222. 11. I.V.Tanaaaav and M. I. Lavina, Zh. Analit. Khim. 1946,1,224. 12. F. N. D&hman and I. V. Tananaev, Kh&n. Re&iti Elemen&o, Akad. Nauk SSSR Znrr.Obskh. Khim., 1955,2,37. iNa 13. I. V. Y--ananaev and M. I. Levina, Zk At&it. Khim.. 1947,3,31. 14. W. U. Maiik and A. K. Bhat&harya, Agm Univ. J. Research. 1957,1,25. 15. I. V. Tananaev and A. P. Kodkov, Z~lr.Akrrd N&k. SSSR Neorgon. Materio&. 1955,1,607. 16. A. K. Bbamwharya and H. C. Gaur, J. India Chem. Sot., 1948. U, 185 17. Z&m, ibid., 1948,28,X2@. 18. H. S. Harned and B. 0. Gwen. * Physical Chemistty of EIrerro&ic Solutions, Reinhold, New York, 1964. 19. G. Barbemi. ELwwtidlmatematkzagenerale, Casa Editria Macri. Fiienzc, 1945. 20. F. J. C. Rossotti, in Mb&n coOr&mzr~or~ Ckmtstry, edited J. Lewis and R. G. Wii, Interscience. New York, 1960. 21. L. E. Orgel, Zntroduzi~ a& chiti dei met& di transiztone, Feltriuelli editom, Milano. 1963.
maddanodath
-
of 293-q&o-1
(Received20 Jorwrry 1972. Accqted 20 Febrqv
1972)
tica tba prqmration of 2,3q&&@ithioI (H,qdt) by Morrison and Furst in 19%: moll)r publica~~itara8aananalytiadlwgonthavcappcared.~ lnfbmtacionontbepqertiesofthe owew, and a8 yet there are no pubii&ed data on the ioaixation constants. ~tlqelfssaucqh teva&wd and M attempted to obtain these constants by a spectrophotometric method but concludcd~thotthcywmtooclosetobed~bysuchmethoda In order fo ratk&kc tha analytical procedures and to predict the optimum working conditions, the ioniaation constants of Ii&t have been dewmined by potentiometric titration and volubility mcasunmmtJ. EXPERIMENTAL %ents 2,3Quinoxa&edithioi. Rqaad as dwaibcd previously‘ and purified by dissolving the crude product in sodium hydroxide, under a nitrogen atmosphere, reptwipitating it with ac&c acid. and repeat@ the process. The product was dried at 100’ under vacuum. Elemental analysis of the purificdmatuialgaveC.49*7%; H,3.3%; N,14.2%; S,32+3%C,&N$,requiresC,49-5%; H,3.1%; N, 144%; S. 33.0%. by mixing Hedt with the calculated ~~hnne of 4M sodium hydroxide and The crude product was pmificd by diilving it in the minimum volume of aqueous ethanol, filtering, and adding a large cxces~ of diethyl ether. The bright vclloworange material was filtered off, washed with ether and dried under vacuum. Elemental analy& of the
Analytical data
1241
disodium salt @hydrate) gave C, 35.2%; H, 3.1%; N, 10.1%; S, 23.3 %; Na, 16.8 %. C,&N,&O,Nas requires C, 350; H, 2.9%; N, 1@2%; S, 23.4%; NO, 168%. Perchloric acid. Prepad by dilution of the anaiytical grade acid and standard&d with sodium carbonate. r~~~maxndcd by Albert and ScrjcanF Bufer solutions. For the pH range 3+1@5 buffer ~0111tion~ were used, and Walpole buffers’ for the pH range 0.7-3.0. Procedure Sodium salts of Htqdt (lOO-ml portions of @OOl-O.OlMsohuions) were titrated potentiometrkahy at 20” under a nitrogen atmosphere with perchloric acid. The titrations were repeated at 25’ and at ionic strength 0.1 (added sodium perchiorate) but no sign&ant ditTerences were observed. Solubiiity measuramarts were carried out by preparing saturated solutions of Hqdt in @lM sodium chloride and OOOSMbuffer, equilibrating them by shakin for 3 hr at constant temperature, dtinthetiltrateabsorptiomemcal * ‘Y tiherin ,measuringtbepHofthtfiltrateanddetenniningtbsHq as the fZn(qdt)Js- complex, at pH 10 and 390 nm.
RESULTS AND DISCUSSION The sodium salts are much mom soluble than Hqdt in water, e.g., up to 2iU sohttions of the disodium salt can be prepared, and Nasqdt.2HsO provides an excellent form of the analytical reagent because of its relative stability. Potentiometric titration of @OlM Na,qdt with perchloric acid dearly imk!atesrhcdibaskcbamcw of the reagent (see Fig. 1). The region of the titration curve cormsponding to addition of up to one equivalent of acid was used directly to obtain Ks by the method of Albert and &r&ant. Typical results are shown in Table I. The mean v&e an B spread found at 20” were 9.95 f @03. pKl could not be obtained diiy because H&t precipitated on addition of more than one qmvalent of acid. For this region of the titration curve the method of Dyrsseo and Hock: as de+ scribed by Ring.* was therefore used. By applying the condition of electronewaky to points on the curve correspondin to a saturated solution of H dt (see Fig. l), a series of vahres for the solubility *“i results are shown in Table IL The mean vahm product z = VI+1kq dr] was obtained. Typlca
PH
I I
Equivdents FIG. I.-Potentiometric
I
2 of acid
titration of 091M2.3quinoxalinedithiol @sodium salt) with 0482M perchloric acid (20”). 0 Bxperhnental points 0 Pomts calculated for pK, = 6.84 Quecipitation of Hqdt occurred from pH 8.9 downwards).
Analytical data TILE DITIiIOL
I.-D
@OlM
AT
BlBRWNATlON
OF
FROM m
#,
OF
mUnON
CON cENTRATION
AND
-c
ml
PH
qdt*prascnt, mmob
i.2 0.4 0.6 0.8 1.0 1.2 1.4
10.93 10.75 1050 10.30 10.10 990 9.73 9.0
0.8414 0.7450 06486 0.5522 0.4558 0.3594 0.2609
Titrant,
01
~,%QUlNOXALlNEITS DIWXBIUM
20” (m: ACED)
SALT
O-48W
PK*
O-9378
-0.79 -0.53 -0.32 -0.14 +0.03 +0.21 +@42
994 997 9.98 9-96 9.93 994
9.92
+ oop - hy&oxyl ion activity. TABLE~.-&3XRMINATTON #JIBMIoLBIRIc
lTlXA7SON
OF OF
THE ITS
SOLUMJTY DISOWJM o482M
Hqdt- titrated, mmele P=s
0.1928 10.88
PRODUCC
(&)
AT
O.OlM
PBRciiLumc
ACLD)
SALT
02892 10.89
OF
@3856 10-95
227
CON cENTRATION
04020 10.89
and aBmpd found for pK, at 20” wet-a1091 f 094. Tha sohtbility of ut+&sd at 20 , was 72 x 10- M. pK, was calculated by usmg the rciattonshtp Kl
Faobs MD
w
05784 1094
(lTWNT:
0.6784 10.88
H,qdt (SJ, mcasumd
9= [H+lWqW _ 5
[Hsqdtl
6,
The valut found for pKx was 6-80 & OW. Similar results wera obtained from potcntiomctric titration of the monosodhnn salt of H, dt. Measuranents of solubilitics in b9 crad solutions showed that the solubility of Hlqdt remains constant in tha pH range @7-5.0 and is equal to S,. Above pH 5 thcra is a ma&cd incream in solubility. Solubilitiu in the pH ranga 54-85 wcra used to obtain pKr by the m&hod of Krcbs and Spcak~IU,~ also dascribcd by King: The &avant equation is: =pH-pK, whera S is tha solubility of Hqdt at a given PH. The pK, value obtained gra * y by this mathod was 686 at 20’. Above pH 85 H,qdt becomes cxtrcmciy soluble and the sol Jhrcah ility m&hod cannot ba uxd to d&amine K,. The avcraga vs ucs of the constants found in the resent work ara p& = 6.84 and pK, = 9.95. dad asscntiaily as the “mix~’ act*%* mnization constants since activity corraxions * tions were car&d out in solutions not stronger than “YE$$!arHowcvcr as tha datumma O.OlM, tha v&t; of the tbdnnoayaMlic constants may not ba signi6cantly d&rent. The two pK values arc sufIi&ntly far apart to be dcuxmincd scquauiaily with good pmcision. It can ba conch~dcd that Hsqdt behaves as a d&sic acid and is not itself protonatcd at pH values not bciow o=I. Lower pH values wcra not investigated. It would be of in&rest to know whether the acid protons arc associatedwith sulphur or nitrogen atoms. The foilowing cxtrcmc structm~ of H,qdt arc possible
Analytical data
1243
as well as thiol-thione tautomeric forms .l” The absence of any basic (proton-acceptor) properties in H,qdt suggests structum (I) as the most probable. Other work carried out in these laboratories.‘e particularly infrared spectroscopic and preparative evidence, supports this view, which has bearing on the applications of Hsqdt as an analytical teagent. Acknow&~ement~-We technic to A. K. S.
acknowledge with gratitude the grant of study leave from Kingston PolyJ. A. W. DALP~L A. K. S~~wrnatrr+
Department of Chemistry Chelsea College of Science and Techdogy Manresa Rot& London, S. W.3.
address: School of Chemical Science and Technology, Kingston Kingston-upon-Thames, Surmy, U.K.
*Present
F~~~odium salts of 2,3quinoxallnedithiol have heen prepared and used for de&mutation of the acid ionization constants by potentiometric titration. The fully protonated form of the reagent was used in an alternative determination of the first ionization constant by a solubility method. The constants are pK, = 684 f 0=04 and
PKt = 9.95 f 0=03. s wurdcn Natium Salae von 2$Chinoxalindithiol vorbemitet und zur Ermittlung der S8ureionisationskonstanten durch potentiometrische Titrierung benutzt. Dii vollig protonierte Form des Reagenz wurde mit einem L&lichkeitsverfahren in einer anderen Featstellung der ersten Ionisationskonstante venvandt. Die Konstanten sind p& - 684 f 0,04 und pKs = 9,95 f 0,03.
z
R&m&-Gn a prepare les sels de sodium du 2.3 uinoxahnedithlol et les a utiIi& pour la d&ermination des constantcs I**tonisation acides par titrage potentiom&rique, On a utilis6 la forme totalement proton& du rdactif dans une autre posaibilit6 de d&uminatlon de la constante de pmmiixe ionisation par une m6thode de solubilitd. Les constantea sont p& = 6,84 & 0,04 et pK, - 9,95 f 0.03. REFERENCES D. M. Morrison and A. J. Furst, J. Org. Chem., 1956,21,470. e.g.. R. W. Burke and E. R. Deardortf, Takmta, 1970,17,255 and refemncea therein. D. B. Stevan&vid and V. G. D&i& Bull. Inst. Nuclear Sci., Boris Kidrich, Be&a&, 1959.9.69. J. A. W. Dalziel and A. K. Slawinski. Tdanta. 1968. Is. 367. A. Albert and E. P. Serieant, Zonizat&n Const&ts ofsAc& ad &ues, Mcthwn. London, 1962. A. I. Vogel, A Textbook of Qutmtitative Itwtpnic &dysis, 3rd Ed., b, London; 1961. D. Dvmsen and B. Hoek. Svensk. Kern.Tidskr.. 1952.64.80. E. J. king, Acid-&rPc E@ibria, Pqamon, &ford, I%5. H. A. K&s and J. C. Speakman, J. Chem. Sot., 1945,593. 10. A. K. Slawinski, Ph.D. lResis, University of London, 1970. 1. 2. 3. 4. 5. 6. 7. 8. 9
1240
Etbd-On a etFectu6 du Ltudcs potentiom&ique et de solubilit6 d@ fcrroqwluru de nickel, cobalt. mallxall&8c(lI) et cadmium toutea
REFERENCES 1. A. Bellomo. T&n&, 1970.17,1109. 2. A. Bellomo, D. De Marco and A. CaJak. Proc. 2nd Conf. Appl. Phy. Gem. 4th Symp. Oscillometry, vazpcem, Hungary, 1971. 3. K. L. Cbang. Anal. Chem., 1955.23.1594,. 4. G. Jander and H. W&t, Lehrbuch dcr amalyttichen undpr&watioen uno~chen Chemie, Hiczl v&g, stuttgart, 19s9. 5. W. Pmndtl, 2. Anorg A&em. Chem. 1932,208,420. 6. I. V. Tananaev and M. A. Cluskova, Zh. Prikl. m., 1959,32,1899. 7. I. M. Koltoff and A. plcuson, Znd. Gem., Anal. Ed., 1945,4,171. 8. E. L. Nima, R. E. Hamm and G. L. ?ec ’ , Anal. Chem. 1950,22,970. 9. D. F. Swinehart, ibti., 19Sl,23,381. 10. J. S. Bcshmukb and M. Vmucopakm, J. ZndlrmChm. Sot., 1957,33,222. 11. I.V.Tanaaaav and M. I. Lavina, Zh. Analit. Khim. 1946,1,224. 12. F. N. D&hman and I. V. Tananaev, Kh&n. Re&iti Elemen&o, Akad. Nauk SSSR Znrr.Obskh. Khim., 1955,2,37. iNa 13. I. V. Y--ananaev and M. I. Levina, Zk At&it. Khim.. 1947,3,31. 14. W. U. Maiik and A. K. Bhat&harya, Agm Univ. J. Research. 1957,1,25. 15. I. V. Tananaev and A. P. Kodkov, Z~lr.Akrrd N&k. SSSR Neorgon. Materio&. 1955,1,607. 16. A. K. Bbamwharya and H. C. Gaur, J. India Chem. Sot., 1948. U, 185 17. Z&m, ibid., 1948,28,X2@. 18. H. S. Harned and B. 0. Gwen. * Physical Chemistty of EIrerro&ic Solutions, Reinhold, New York, 1964. 19. G. Barbemi. ELwwtidlmatematkzagenerale, Casa Editria Macri. Fiienzc, 1945. 20. F. J. C. Rossotti, in Mb&n coOr&mzr~or~ Ckmtstry, edited J. Lewis and R. G. Wii, Interscience. New York, 1960. 21. L. E. Orgel, Zntroduzi~ a& chiti dei met& di transiztone, Feltriuelli editom, Milano. 1963.
maddanodath
-
of 293-q&o-1
(Received20 Jorwrry 1972. Accqted 20 Febrqv
1972)
tica tba prqmration of 2,3q&&@ithioI (H,qdt) by Morrison and Furst in 19%: moll)r publica~~itara8aananalytiadlwgonthavcappcared.~ lnfbmtacionontbepqertiesofthe owew, and a8 yet there are no pubii&ed data on the ioaixation constants. ~tlqelfssaucqh teva&wd and M attempted to obtain these constants by a spectrophotometric method but concludcd~thotthcywmtooclosetobed~bysuchmethoda In order fo ratk&kc tha analytical procedures and to predict the optimum working conditions, the ioniaation constants of Ii&t have been dewmined by potentiometric titration and volubility mcasunmmtJ. EXPERIMENTAL %ents 2,3Quinoxa&edithioi. Rqaad as dwaibcd previously‘ and purified by dissolving the crude product in sodium hydroxide, under a nitrogen atmosphere, reptwipitating it with ac&c acid. and repeat@ the process. The product was dried at 100’ under vacuum. Elemental analysis of the purificdmatuialgaveC.49*7%; H,3.3%; N,14.2%; S,32+3%C,&N$,requiresC,49-5%; H,3.1%; N, 144%; S. 33.0%. by mixing Hedt with the calculated ~~hnne of 4M sodium hydroxide and The crude product was pmificd by diilving it in the minimum volume of aqueous ethanol, filtering, and adding a large cxces~ of diethyl ether. The bright vclloworange material was filtered off, washed with ether and dried under vacuum. Elemental analy& of the
Analytical data
1241
disodium salt @hydrate) gave C, 35.2%; H, 3.1%; N, 10.1%; S, 23.3 %; Na, 16.8 %. C,&N,&O,Nas requires C, 350; H, 2.9%; N, 1@2%; S, 23.4%; NO, 168%. Perchloric acid. Prepad by dilution of the anaiytical grade acid and standard&d with sodium carbonate. r~~~maxndcd by Albert and ScrjcanF Bufer solutions. For the pH range 3+1@5 buffer ~0111tion~ were used, and Walpole buffers’ for the pH range 0.7-3.0. Procedure Sodium salts of Htqdt (lOO-ml portions of @OOl-O.OlMsohuions) were titrated potentiometrkahy at 20” under a nitrogen atmosphere with perchloric acid. The titrations were repeated at 25’ and at ionic strength 0.1 (added sodium perchiorate) but no sign&ant ditTerences were observed. Solubiiity measuramarts were carried out by preparing saturated solutions of Hqdt in @lM sodium chloride and OOOSMbuffer, equilibrating them by shakin for 3 hr at constant temperature, dtinthetiltrateabsorptiomemcal * ‘Y tiherin ,measuringtbepHofthtfiltrateanddetenniningtbsHq as the fZn(qdt)Js- complex, at pH 10 and 390 nm.
RESULTS AND DISCUSSION The sodium salts are much mom soluble than Hqdt in water, e.g., up to 2iU sohttions of the disodium salt can be prepared, and Nasqdt.2HsO provides an excellent form of the analytical reagent because of its relative stability. Potentiometric titration of @OlM Na,qdt with perchloric acid dearly imk!atesrhcdibaskcbamcw of the reagent (see Fig. 1). The region of the titration curve cormsponding to addition of up to one equivalent of acid was used directly to obtain Ks by the method of Albert and &r&ant. Typical results are shown in Table I. The mean v&e an B spread found at 20” were 9.95 f @03. pKl could not be obtained diiy because H&t precipitated on addition of more than one qmvalent of acid. For this region of the titration curve the method of Dyrsseo and Hock: as de+ scribed by Ring.* was therefore used. By applying the condition of electronewaky to points on the curve correspondin to a saturated solution of H dt (see Fig. l), a series of vahres for the solubility *“i results are shown in Table IL The mean vahm product z = VI+1kq dr] was obtained. Typlca
PH
I I
Equivdents FIG. I.-Potentiometric
I
2 of acid
titration of 091M2.3quinoxalinedithiol @sodium salt) with 0482M perchloric acid (20”). 0 Bxperhnental points 0 Pomts calculated for pK, = 6.84 Quecipitation of Hqdt occurred from pH 8.9 downwards).
Analytical data TILE DITIiIOL
I.-D
@OlM
AT
BlBRWNATlON
OF
FROM m
#,
OF
mUnON
CON cENTRATION
AND
-c
ml
PH
qdt*prascnt, mmob
i.2 0.4 0.6 0.8 1.0 1.2 1.4
10.93 10.75 1050 10.30 10.10 990 9.73 9.0
0.8414 0.7450 06486 0.5522 0.4558 0.3594 0.2609
Titrant,
01
~,%QUlNOXALlNEITS DIWXBIUM
20” (m: ACED)
SALT
O-48W
PK*
O-9378
-0.79 -0.53 -0.32 -0.14 +0.03 +0.21 +@42
994 997 9.98 9-96 9.93 994
9.92
+ oop - hy&oxyl ion activity. TABLE~.-&3XRMINATTON #JIBMIoLBIRIc
lTlXA7SON
OF OF
THE ITS
SOLUMJTY DISOWJM o482M
Hqdt- titrated, mmele P=s
0.1928 10.88
PRODUCC
(&)
AT
O.OlM
PBRciiLumc
ACLD)
SALT
02892 10.89
OF
@3856 10-95
227
CON cENTRATION
04020 10.89
and aBmpd found for pK, at 20” wet-a1091 f 094. Tha sohtbility of ut+&sd at 20 , was 72 x 10- M. pK, was calculated by usmg the rciattonshtp Kl
Faobs MD
w
05784 1094
(lTWNT:
0.6784 10.88
H,qdt (SJ, mcasumd
9= [H+lWqW _ 5
[Hsqdtl
6,
The valut found for pKx was 6-80 & OW. Similar results wera obtained from potcntiomctric titration of the monosodhnn salt of H, dt. Measuranents of solubilitics in b9 crad solutions showed that the solubility of Hlqdt remains constant in tha pH range @7-5.0 and is equal to S,. Above pH 5 thcra is a ma&cd incream in solubility. Solubilitiu in the pH ranga 54-85 wcra used to obtain pKr by the m&hod of Krcbs and Spcak~IU,~ also dascribcd by King: The &avant equation is: =pH-pK, whera S is tha solubility of Hqdt at a given PH. The pK, value obtained gra * y by this mathod was 686 at 20’. Above pH 85 H,qdt becomes cxtrcmciy soluble and the sol Jhrcah ility m&hod cannot ba uxd to d&amine K,. The avcraga vs ucs of the constants found in the resent work ara p& = 6.84 and pK, = 9.95. dad asscntiaily as the “mix~’ act*%* mnization constants since activity corraxions * tions were car&d out in solutions not stronger than “YE$$!arHowcvcr as tha datumma O.OlM, tha v&t; of the tbdnnoayaMlic constants may not ba signi6cantly d&rent. The two pK values arc sufIi&ntly far apart to be dcuxmincd scquauiaily with good pmcision. It can ba conch~dcd that Hsqdt behaves as a d&sic acid and is not itself protonatcd at pH values not bciow o=I. Lower pH values wcra not investigated. It would be of in&rest to know whether the acid protons arc associatedwith sulphur or nitrogen atoms. The foilowing cxtrcmc structm~ of H,qdt arc possible
Analytical data
1243
as well as thiol-thione tautomeric forms .l” The absence of any basic (proton-acceptor) properties in H,qdt suggests structum (I) as the most probable. Other work carried out in these laboratories.‘e particularly infrared spectroscopic and preparative evidence, supports this view, which has bearing on the applications of Hsqdt as an analytical teagent. Acknow&~ement~-We technic to A. K. S.
acknowledge with gratitude the grant of study leave from Kingston PolyJ. A. W. DALP~L A. K. S~~wrnatrr+
Department of Chemistry Chelsea College of Science and Techdogy Manresa Rot& London, S. W.3.
address: School of Chemical Science and Technology, Kingston Kingston-upon-Thames, Surmy, U.K.
*Present
F~~~odium salts of 2,3quinoxallnedithiol have heen prepared and used for de&mutation of the acid ionization constants by potentiometric titration. The fully protonated form of the reagent was used in an alternative determination of the first ionization constant by a solubility method. The constants are pK, = 684 f 0=04 and
PKt = 9.95 f 0=03. s wurdcn Natium Salae von 2$Chinoxalindithiol vorbemitet und zur Ermittlung der S8ureionisationskonstanten durch potentiometrische Titrierung benutzt. Dii vollig protonierte Form des Reagenz wurde mit einem L&lichkeitsverfahren in einer anderen Featstellung der ersten Ionisationskonstante venvandt. Die Konstanten sind p& - 684 f 0,04 und pKs = 9,95 f 0,03.
z
R&m&-Gn a prepare les sels de sodium du 2.3 uinoxahnedithlol et les a utiIi& pour la d&ermination des constantcs I**tonisation acides par titrage potentiom&rique, On a utilis6 la forme totalement proton& du rdactif dans une autre posaibilit6 de d&uminatlon de la constante de pmmiixe ionisation par une m6thode de solubilitd. Les constantea sont p& = 6,84 & 0,04 et pK, - 9,95 f 0.03. REFERENCES D. M. Morrison and A. J. Furst, J. Org. Chem., 1956,21,470. e.g.. R. W. Burke and E. R. Deardortf, Takmta, 1970,17,255 and refemncea therein. D. B. Stevan&vid and V. G. D&i& Bull. Inst. Nuclear Sci., Boris Kidrich, Be&a&, 1959.9.69. J. A. W. Dalziel and A. K. Slawinski. Tdanta. 1968. Is. 367. A. Albert and E. P. Serieant, Zonizat&n Const&ts ofsAc& ad &ues, Mcthwn. London, 1962. A. I. Vogel, A Textbook of Qutmtitative Itwtpnic &dysis, 3rd Ed., b, London; 1961. D. Dvmsen and B. Hoek. Svensk. Kern.Tidskr.. 1952.64.80. E. J. king, Acid-&rPc E@ibria, Pqamon, &ford, I%5. H. A. K&s and J. C. Speakman, J. Chem. Sot., 1945,593. 10. A. K. Slawinski, Ph.D. lResis, University of London, 1970. 1. 2. 3. 4. 5. 6. 7. 8. 9