IODINE MONOCHLORIDE ADDED
June 5 , 1961
- 0.052H
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TO P E R H A L O O L E F I N S
Aside from the apparent increased polarizability of I, i t does not, as a “meso-ionic” compound, T are given in Table I11 along with chosen litera- appear to be unusual in its sensitivity to electronic ture constants2 for comparative purposes. effects, nor in its sensitivity to the nature of leaving groups. Thus, the rate ratios k A / k A H and kI :k B r : T.4BLE IIJ kcl compare with those previously listed for other COMPARISON OF THE NUCLEOPHILIC CONSTANT (En)AND nucleophiles possessing high E n value^.^^^ ACIDITY ( H ) FUXCTION O F DEHYDRODITHIZONE TO A SEExperimental LECTED GROUP OF NUCLEOPHILES log ( k / k ~ , o = ) 2.59En
Xucleophile
S ‘ SOa’ 5101-
S
En 3 2 2 2
08 57 52 34
(7)
H
Xucleophile
Ew
H
14 66 9 00 3 60 0 17
(NHa)*C=S CNSCN-
2 18 2 02 1 83 0 59
0 80
SO.’
10 88 (1 00) 3 74
It may be noted that of those nucleophiles which are particularly effective toward the spa carbon, I possesses the lowest value of H . The high values of both En and H possessed by some of the other nucleophiles such as S= and SO2- provide these bases with the ability to undergo displacement reactions a t the sp3 and sp2 carbon atoms. This should not be expected of I on the basis of its very low H value. Experimentally, this is found to be the case, and I, unlike these other bases with large En values, is incapable of displacing p-nitrophenol from p-nitrophenyl acetate. The somewhat higher value of En for I as compared to thiourea and thiocyanate (which also possess the N-C-S configuration) may be attributed to a greater polarizability of the molecule, which might result from its “meso-ionic” structure.
[CONTRIBUTIONFROM
THE
Materials.-Dehydrodithizone was that of another study.‘ Bromoacetamide was prepared by the method of Papenclick.’ The haloacetates were obtained commercially and recrystallized to constant m.p. from petroleum ether. Apparatus.-The determination of pH values was carried out with a model 22 Radiometer p H meter. All spectrophotometric measurements were made with a model PMQ I1 Zeiss spectrophotometer fitted with a special hollow brass cuvette holder thermostated. a t 30 i 0.01” by a Haake constant temperature circulatmg bath. Kinetics.-For iodoacetic and chloroacetic acids the substrate was employed as buffer. For bromoacetamide and bromoacetic acid 0.01 M tartrate buffer was employed. All reactions were followed at ionic strengths (calculated) of 0.125-0.05 M provided by KC1. The disappearance of dehydrodithizone was followed a t 260 mp (Xmsx). Specific procedures for the kinetic experiments and method of calculation of observed rate constatits have been given previously .B
Acknowledgments.-LVe should like to thank hlr. S.A. Mendoza for performing a portion of the experimental work reported herein. This work was supported by grants to J. 0. from The National Heart Institute and to T. C. B. from The National Science Foundation and The National Institutes of Arthritic and Metabolic Diseases. (7) A. Papendick, Ber., 26, 1160 (1892). (8) T. C . Bruice and M. F. hlayahi, J. A m . Chem. Soc., 82, 3067 (1960).
RESEARCH AND DEVELOPMENT DEPARTXENT, PENNSALT CHEMICAL CORP., PHILADELPHIA 18, PA.]
Addition of Iodine Halides to Fluorinated Olefins. I. The Direction of Addition of Iodine Monochloride to Perhaloolehs and Some Related Reactions BY MURRAYHAUPTSCHEIN, MILTONBRAIDAND ARNOLDH. FAINBBRG RECEIVED NOVEMBER 29, 1960 Contrary to prior reports, the addition of iodine monochloride t o chlorotrifluoroethylene is bidirectional and both isomers CFzClCFClI ( I ) and CFClzCFd (11) are formed. The isomer ratio was shown to be temperature dependent with higher temperatures favoring isomer 11. If the reaction is carried out a t 0’ or lower, nearly pure I can be obtained. In the presence of iron, however, the isomer mixture consisted of about 65y0 of I1 even a t 0’. Pure I1 was isolated in quantity from isomer mixtures by the selective reaction of I a t 50’ with chlorosulfonic acid. In the presence of aluminum chloride third possible C2C12FsI isomer, the rearranged CFaCC121, was produced in 100% isomeric purity in low yield. The lo’, but a t addition of iodine monochloride t o 1,l-dichlorodifluoroethylenegave the isomer CFtClCCl21 exclusively a t higher temperatures or in the presence of iron, the isomer CC1,CFzI also was produced. The formation of relatively large amounts of the chlorination product CFzClCCl, was favored under the latter conditions. At 98’ the addition of iodine monochloride to perfluoropropene gave an isomer composition of 91.5y0 CFICFICFtCl and 8.5y0 CF8CFC1CF21. The direction of the thermal addition of fluorocarbon iodides to some fluorinated olefins has been determined. The great utility of vapor-liquid partition chromatography in both the analysis and separation of the addition compounds is described and characteristic elution time ratios for a series of isomeric fluoroiodides are presented.
-
This is the first paper in a series dealing with the addition of iodine halides to fluorinated olefins and is concerned primarily with the direction of addition of iodine monochloride to various perhaloolefins. The Addition of Iodine Monochloride to Chlorotrifluoroethy1ene.-The addition of iodine monochloride to chlorotrifluoroethylene has been reported to give CF2CICFClI (I) as the exclusive IC1 adduct.1S2 We now wish to report that this (1) R. N. Haszeldine,
-7.
Chcm. SOC.,4423 (1952).
addition is in fact bidirectional under the various conditions reported’s2 and that a t the reaction temperatures previously used, i.e. , room temperature to 50°, the adduct actually consists of at least 20-30% of the isomer CFC12CFJ (II).3 (2) J. T. Barr, J. D. Gibson and R. H. Lafferty, J . A m . Chem. Sac., 73, 1352 (19511,did not investigate the structure of the adduct but assigned the structure CFrClCFClI by analogy to other addition re-
actions of the olefin CFr-CFCI. (3) Professor R. N. Haszeldine, University of Manchester, has recently informed us that he has independently discovered that the ad-
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MURRAY HAUPTSCHEIN, MILTONH R A K JAKD ARKOLDH. FAINBERG
l 7 O l . 83
Furthermore, it now has been discovered that the tion with chlorosulfonic acid t o the chlorosulfate isomer ratio 1:IT is temperature dependent with CF2ClCFCIOS02C1, which was renioved after higher temperatures favoring isomer I1 production basic hydrolysis, as the water-soluble sodium chlorou p to a maxirnum of about 60YGof 11. A t tempera- difluoroacetate. This reaction as well as the retures of 0’ or below almost isomerically pure I was action of the chlorosulfate with ethanol and with obtained. Thus a t 0’ and a t -8 to .-so, the ad- ammonia and conversions thereby to the known ducts were 07 and 9870 pure I. The data summa- ester and amide, respectively, also served to conrized in Table I1 (Experimental), runs 1-5, il- firm the structure for 1. lustrate clearly this effect of increasing temperaCFyClCFCII + ClSOjI1 --+ CFnClCFCIOSOzCl turc on isomer composition. On the other hand, ______ if the reaction is carried out in the presence of a S H J S a 0H EtOII reactive form of nietallic iron, such as iron gauze or ferric chloride, the major product is isomer 11, CF..CICOKH? CF?CICOOSa CFzCICOOEt even when the reaction is carried out at 0’. This Isomer I1 would have given carboxylic acid derivaeffect was first noted when the reaction was pertives of dichlorofluoroacetic acid, i.e., CFClzCOONa formed in an iron vessel (run 7, Table 11). By further study of this unexpected result, the cata- CFClnCOOEt and CFC12CONH2. Both of the lytic effect of iron was denionstrated unequivocally novel isomeric chlorosulfates CFzCICFCIOSO&l (run G us. run 2 , Table 11). It should be noted t h a t and CFCl&F20S02Cl formed a t a higher temperadespite temperature variations (in the prese.nce of ture, ie., 1 OO’, have been characterized. Finally, in order t o investigate the effect of iron), there WAS n maximum of about 65F5 of IT in the products. This suggested the possibility another Lewis acid, the reaction of IC1 with CF2= that the isomeric ratio may have been the result CFCl was carried out using a rather large amount of a cheniical equilibrium. This possibility, how- of aluminum chloride. It was a complete surprise ever, was not confirmed. The isomer composi- to discover that the sole IC1 adduct obtained was tions were iiot altered significantly when nearly neither I nor I1 but the new rearranged product pure isomer I or isomer I1 was heated a t -10-50” in CF&XlzT! Only 15yc of the total product was the presence of iodine monochloride and iron. the IC1 adduct; 60% of the product consisted of Thus iron was shown not t o be a catalyst for “equi- isomerically pure CCIBCCIFz; 15% of C2C13Fa (mostly CF3CCla); and the remainder consisted libration” of the mixture. principally of CC12=CC1F, CC12=CC12 and inThe reaction has been carried out in the presence and absence of solvents. At low temperatures terestingly CF2=CC11. CF3CCI2I also has been (below 0’) the heterogeneous reaction of solid IC1 prepared by the now1 and much superior method the addition of iodine monofluoride (IF6 with CF2=CFC1 is very slow and use of a solvent iilvolving 21z -+ 5IF) to CF2=CC12.6 This reaction can is advantageous. Methylene chloride and 1,2,2trichlorotrifluoroethane have been employed, al- uive either CF3CC12Tor the previously characterized though the solubility of the IC1 in the latter is ?FClaCFzI (IT). The ultraviolet maximum in isolow and therefore the use of trichlorotrifluoroethane octane a t 296 n1i.l was consistent only with the is not recommended. The most efficient reaction structure CF:iCC121. The Addition of Iodine Monochloride to 1,lsystem is the solution of the reactants in I, itself. Dichloro-2,2-difluoroethy1ene.-The addition of IC1 The pure isomers could be separated by vapor- to CF2:=CC12 was next examined.’ This reaction liquid partition chromatography (V.L.P.C.); see also was found to be bidirectional but t o a lesser Table I. The ultraviolet spectra in isooctane extent than in the case of the addition of IC1 to exhibited maxima a t 286 mp for I and a t 274 mp CF,-=CFCl. At -lo’, CF2C1CC121 was profor IT which are entirely consistent with the re- duced in lOO?{ isomeric purity ( i e . , to the limit of spective CF&lCFClI and CFC12CFJ structures. detection, which is less than O.jYG, in this case). It should be noted in this connection that a mix- Lit0-3’ the adduct consisted of 99% CF2ClCC12I ture of isomers I and I1 will show an unresolved and 1% CClYICF2I. At 5 t o 15’ the isomeric single maximum (rather than two maxima) at purity of the adduct CF2C1CC121ranged from 98 some wave length intermediate between 286 and t o 9 i ~ & . Litabout 20’, using a reverse addition 274 mp with the position dependent on the iso- procedure, an isomer mixture consisting of about meric composition. Thus mixtures containing, for 90Yc CFnCICClzIand I ClycCClaCF?Twas obtained. example, 75, 60 and 25yo of I, will have respective In thc presence of iron a t temperatures between 5 maxima a t 283, 281 and 277 mp. and 13’ the adduct contained about 20y0 of cc13A previously discovered reaction of fluorocarbon CFzI. The higher temperatures had an even more iodides with halosulfonic acid t o produce fluoro- profound effect on the formation of the undesired carbon halosulfates5 and carboxylic acids there- chlorination by-product CCI:3CF2Cl. Thus a t 0-3’ from5 was employed advantageously to effect the only 1% of the total product was CC13CF2C1while separation of pure TI in sizable quantities. Thus the addition of CF2==CC12t o IC1 a t about 20’ rea t a temperature of about SOo, isomer I was sulted in the formation of about 20Tc of the tetrapreferentially and completely converted by reac- chlorodifluoroethane.
4
i
1
+
dition of iodine monochloride t o chlorotrifluoroethylene can be bidirectional and t h a t the direction of radical attack on perfluoropropene may also be varied. (4) See R . N. Haszeldine, J . Chein. Soc., 1764 (1953),for ultraviolet spectroscopic data. Braid, . forthcoming putilientiona. (6) M . Hauptschein and >I
( 6 ) hi. Hauptscheiri and hi. Braid, forthcoming publication. which also describes the addition of I F t o CFz=CFCI and t o CFz=CFCFa to give CFsCFClI + CFd21CF21 and C F C F I C F B ,respectively. The respective V.L.P.C. elution time ratios of these compounds have been included in Table I for completeness. (71 R N H:hcvddine. C a n a d i n n Patent 603.718 (1860).
June.5, 1961
IODINE TO NO CHLORIDE ADDEDTO PERHALOOLEFINS
The isomers were separated by V.L.P.C. AS would be expected, the ultraviolet maximum (in isooctane) for CF2ClCClzI a t 302.5 mp is much higher than the maximum for CC13CFJ which is a t 274.5 mp. The infrared absorption spectra of both of these isomers were different from that of the other Dossible isomer. the verv unlikelv rearranged produrt CC12FCC1F18 prep&ed by 'addition of IC1 to CFCl=CFCl. The Addition of Iodine Monochloride to Perfluoropropene.-The products of a related reaction which preceded the aforementioned work were next re-examined. The reaction of perfluoropropene with iodine nionochloride a t 98' was shown to produce an adduct consisting of 91.5y0 CF3CFICF2C1 (ultraviolet maximum in isooctane at 277.5 mp; compare C2F6CFICF3 A, 279 mp) and 8.5% CF3CFC1CF21 (ultraviolet maximum in isooctane at "73 nip). On the basis of the previously discussed studies it would appear likely that the yield of CFjCFICF2Cl would be increased by decreasing the reaction temperature and that iron may possibly function as a catalyst to raise the yield of CF3CFClCF21. Chain Transfer Efficiencies and Miscellaneous Te1omerizations.-The discovery of the bidirectional nature of the addition of IC1 to C F F C F C l and of methods for preparing the individual isomers is of more than cursory interest. Isomer I is much more active than I1 as a chain transfer agent for various telomerization reactions. In the thermal telomerization of CFZ=CFCl, for example, I is effective both as an initiator and as a chain transfer agent a t 160°, a t which temperature little reaction occurs if I1 is used instead as the telogen. In the latter case a reaction temperature of a t least 185' is necessary and this telomerization process is not nearly as well controlled. Greater quantities of solid telomers consequently are formed in the resulting wider spread in molecular weight ranges.5 Also where I has been used as a means of introducing the perfluorovinyl group, e.g.
2497
analytical technique it has now been determined for two specific cases that the 1:1 adducts of CF3I and n-C3F71 with CF2=CFCFs had isomeric compositions of 92% CF3CF2CFICFa and 87, CF:+2F?(CF&CFCF21for the former and of CF2CF2CFICFs and 2% CF3CF2CF2CF(CF3)CF?I for the latter adduct. It was previously shown by V.L.P.C. that the composition of the 1: 1 adduct of the thermal reaction of n-CaF71 with CHZ=CFZ was 95% CsFiCHzCF21and 5% C3F7CFzCH21. lo Unpublished observations by the authors also indicate that the 1: 1 adduct of the thermal reaction of CF2ClCFClI with CF2=CFCl consists of a few per cent. of CF2ClCFC1CFC1CFzI in addition to the main product, CF&1CFC1CF2CFClI. In view of all of the above findings, i t should be expected that the products resulting from the thermal telomerizations of unsymmetrical olefins will generally contain a t least a small percentage of other isomers. Vapor-Liquid Partition Chromatography.--During the course of this research a careful study was made of the use of vapor-liquid partition chromatography as a tool for the analysis and separation of closely boiling isomeric perfluoro- and perfluorochloro-alkyl iodides. Table I summarizes their characteristic elution time ratios, t c l ' t ~ ~ lin , , three different chromatographic columns for the temperatures indicated. This ratio is that of the elution TABLE I V.L.P.C." ELUTIONTIMERATIOSOF IsoCHARACTERISTIC XERIC FLUOROIODIDES Structural formulas
Molecular formula
----tc/lcclr at is0-? "B"b "K"C '6R"d
0.16 0.13 0.18 .22 .24 .27 .29 .21 .32 CrFd .43 .36 .32 .62 .34 .66 C E F ~ .77 .52 .90 .53 .66 .60 CzClFlI .59 .85 .70 -HI I f CHz=CFi +CF2ClCFClCHzCFzI -+ .88 .76 .76 C3ClFJ Zn 1.02 1.30 1.26 CFzClCFClCH=CFz +CFL=CFCH=CF~, 2.6 3.7 3.0 etc., it is obvious that the presence of I1 would 2 . 9 4.6 3.4 result in reduced yields and/or side reactions. 4.0 CFaCClgI 3.2 6.0 The efficiency of a fluorocarbon iodide acting CClaCFzI 8 . P 10.1' as a chain transfer agent is related to the stability CzCl3FiI 10.5" 13.OB CClFzCClzI of the C-I bond, which to a first approximation a V.L.P.C. = Vapor liquid partition chromatography. may be considered as varying inversely with the * Perkin-Elmer 2 meter "B" column (di-2-ethylhexyl wave length of the maximum in the ultraviolet sebacate stationary liquid phase). Perkin-Elmer 2 meter spectrum. It has been found5 that CF3CC121 "K" column (Carbowax 1500). Perkin-Elmer 2 meter (296 mp) and CF2ClCC121 (302.5 mp) are in fact "R" columno (Ucon polygiycol LB -550-X). e Temperathe most efficient of the C2CI2F3I and C2C13F21 ture was 100 . f M. Hauptschein and A . V. Grosse, J . A m . Chem. SOC., 73,2461 (1951). 0 See ref. 6. C3F?I
{ { { { {
CF3CFzCFzIf CFsCFICFao (CF3)zCFCFzI CF3CFzCFICF3 CF,CFzCF2CF( CF3)CFsI CFaCFzCFzCFzCFI CF3 CFzClCFzI' CF3CFClI' CFsCFClCFzI CFaCFICFtCI CFClzCFzI
{
series in agreement with the above theory. The direction of the thermal addition of CFBI and of n-C3F,I to perfluoropropene previously has been shown by chemical and/or ultraviolet spectroscopic evidence to produce RfCF2CFICF3 where Rf= CF3 or ~ - C ~ F By T . the ~ more refinedV.L.P.C. (8) M. Hein, Ph.D. Thesis, University of Colorado, Boulder, Colo., 1934. (8) M. Hauptschein, M. Braid and 79, 2648 (1867).
F.E. Lawlor, J . Am. Chrm, Soc.,
time for the compound to the elution time for the reference standard, carbon tetrachloride (both measured from the time of emergence of the air peak). This ratio is a characteristic constant for each compound in the specified column a t the stated temperature, and is independent both of column parameters such as column length, di(10) M . Hauptschein and R. €3. Oerterlins, i b i d , , E l , 2868 (lQ60),
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J I U R R A Y HRUPTSCMEIN, !VfILTON
BRAIDA N D ARNOLD H.
Vol. 83
I;AINBERG
T A B L E 11 REACTIONS OF IODISEMOSOCIILORIDE WITH CHLOROTKIFLUOROETHYLENE I
