LONG-LIVED PERHALOGENATED FLUORO-CONTAINING ALLYL

CATIONS

V. A. Petrov, G. G. Belen'kii, and L. S. German UDC 543.422.25:547.413.5'i61-128.4

Polyfluoro-containing propenes, like perfluoropropylene [i, 2], 2-H-perfluoropropylene [i, 2], and trifluorotrichloropropylene [3], in the presence of SbF5 either form condensa- tion products with fluoro-containing ethylenes or dimerize, for example [3].

CCI~--~CCI--CF3 sbF$ [CCI~--CCI--CF2]| e CF,=Cr,, CCI2----CCI--CF=CF~CFa

A scheme was postulated for these reactions, which includes the formation of the poly- halogenated allyl cation as the attacking particle. The present paper is devoted to a direct proof of the existence of such intermediates.

The first formation of a perhalogenated cation by the treatment of perchloropropylene with Lewis acids (AICI3, etc.) was recorded by the IR spectroscopy method [4]. Attempts to observe the allyl cations from perfluoropropylene [5, 6] and perfluorocyclobutene [6, 7], using SbF5 as the fluoride ion acceptor, by the ~gF NMR method proved unsuccessful. However, it was found that replacing the I-F atom in perfluoropropylene by an electron-donor substi- tuent, for example, the p-methoxyphenyl group, permits recording the corresponding cation by the ~gF NMR method in SOz solution [5].

5IeOC~H4CF---~CFCF3 ~ [MeOC~H4CF"-'CF'-"CF~] | SO2

An analogous procedure was used to record the aliyl cation from methoxyperfluorocyclo- butene by the ~H and 19F NMR method, in which connection in the latter case the cation was isolated as the solid salt [7].

F F

OMe

SbF.

SbF F SO2

F F

Using SbCI5 as the fluoride ion acceptor, we were also unable to record the corre- spondingallyl cation from l,l,2-trichlorotrifluoropropylene (I) by the 19F NMR method in S02CIF solution at --50 to 0~

The above described unsuccessful attempts to detect fluoro-containing allyl cations by the NMR method are possibly related to the use of such solvents as S02 or S02CIF, which weaken the force of ~F5 as a fluoride ion acceptor and possibly increase the total nucleo- philicity of the medium.

Actually, it proved that the use of pure SbF~ both as the fluoride ion acceptor and the solvent permits observing the corresponding allyl cations from ~), l,l-dichloroperfluoro- isobutylene (II), and l,l,2-trichloroperfluoro-l-pentene ~II) by the 19F and l~C NMR method at the usual operating temperature of the NMR spectrometer data unit.

A. N. Nesmeyanov Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 438-441, February, 1984. Original article submitted May 31, 1983.

402 0568-5230/84/3302-0402508.50 �9 1984 Plenum Publishing Corporation

TABLE i.

Compound '1

(I)

(~a)

(ii)

(IIa)

(III)

(IIIa)

~C NMR Spectra of (1)-(llI) and (la)-(ilIa)

i29A

204,i

142

2t4,~

131,3

212,9

6, ppm

i21

l~6,i

i22

~t3,8

i26,i

133,6

~a

119,7

~71,6

i20,4

i73,6

112,4

t75,5

i

C~

t17,6

i0K2

107,9

C5

['. 6

k ,6

J , Hz

C~-F=274 C2-F=39,3

C~-FACm=366,5 C~-FstA)=344,8 Ca-FAts~=I8,3 C'-FAcm=21,4 C3-F=277, C2-F=34

C3-FA=C~-FB=357,7 C' - -FA~B)= iT , i CZ-FA~m=i2,2 O-F~=279,5 C ~-F~=39

C 3-Fa=26i,2 C~-F~=268,6 C5-Fc=285,6

C ~-Fa=371,1 C~-F~=261,i C~-Fc=291 C~-Fa=5 C3-Fb=29,3 Ca-Fa=37,1 Cr C~-Fb=34.2

2

GCI F A 1 ~ a SbF~ I ~ + %3 / CCI~=CCI--CFs ~ CC12 C

(I) (Ia) "NFB 4 CF~ 21

CFa C FA 1 2] 3 SbF~ 1 ,Z"" + "'~, 3 / CCIz=C--CF8--> CCI~ C

\ FB

(II) (IIa) "2

CC1 1 2 3 4 5 SbF~ 1 . / ' + " N 3 4 5 CCI:=CCI--CF2CF~_CFs > CCI~ CF--CF=CFa

a b c a b c (m) (UIa)

Thus, in the ~gF NMR spectrum of a solution of olefin ~) in SbFs, the signal of the starting olefin is absent and an AB quartet is present, which is shifted sharply downfield relative to the signal of the starting olefin.

The presence of an AB quartet indisputably proves the appearance of double bonding be- tween the C 2 and C 3 atoms in cation ~ a), and due to this a magnetic nonequivalence of the fluorine atoms appears in cation (la). The ~C NMR spectrum of cation (la) contains three signals, whose multiplicity differs substantially from the splitting of the signals of the precursor. Two of these signals, and specifinally of C ~ and C 3, are respectively shifted downfield (relative to the precursor) by 74.7 and 51.9 ppm, while the C 2 signal is shifted upfield by 5 ppm. This order of change in the chemical shifts corresponds both to the theoretical concepts regarding charge distribution in allyl cations and the experimental data that were obtained for hydrocarbon allyl cations [8].

In addition, an increase is observed in the absolute values of the ~3C--ZgF SSCC when compared with the starting olefin. Analogous changes in the chemical shifts and SSCC occur in the spectra of cations (Iia) and (IIIa).

403

TABLE 2. 19F NMR Spectra of (I)-(IlI) and (la)-(Illa)

Compound

(:)

(Ia)

.(II) (Ha)

(lid (llla)

6,:ppm

CF,

- i 6

-i7,8 -9,6

F A

: i0 i , l

- 10O

FB

-92,8

-97,i

Fa

27,9 -60,5

Fb

47,5 38,3

Fc

3,7 2,9

J, ppm

"/AB = 245

lAB = 243

]CF~FA(B) = 28

]CFs_FB (A) =ll

It should be mentioned that in all of the above described cases the signals of the C: and C ~ carbon atoms, which bear a positive charge, are found somewhat upfield from the analo- gous signals of the hydrocarbon allyl cations [8]. This is possibly related to a partial quenching of the positive charge due to the "reverse feeding" of the electron density from the halogen atoms, including fluorine, to the positively charged carbon.

We were also unable to record by the NMR method the corresponding allyl cations from perfluoropropylene, 2-Cl-perfluoropropylene, 2-H-perfluoropropylene, and perfluoroisobutylene. Complex signals were detected downfield (--i00 ppm from CF3CO0~ in the ~gF NMR spectra of these cations. A detailed analysis of these spectra will be published later.

EXPERIMENTAL

Starting olefins (I)-(III) were synthesized as respectively described in [9, i0, 3].

The 19F NMR sPectra were recorded on a Perkin-Elmer R-32 instrument (84.6 MHz), and the chemical shifts are given in ppm relative to CF3COOH (external standard). The :3C NMR spectra were recorded on a Bruker WP-200SY instrument (50.3 MHz), using TMS as the external standard. The spectra of cations (la)-(IIIa) were taken at the usual operating temperature of the NMR spectrometer data unit.

Preparation of Solutions of Allyl Cations. Freshly distilled SbF5 was poured into the glass ampul used to take the NMR spectrum and then at ~20~ or with slight cooling was added dropwise the starting olefin in 1/3 of the amount of SbF5 by volume. The ampul was sealed and the contents were mixed well to form a homogeneous solution. The NMR spectra are given in Tables 1 and 2.

CONCLUSIONS

The fluoro-c0ntaining perhaiogenated allyl cations, postulated previously as the inter- mediates in the electrophilic alkenylation reactions of fluoroethylenes, were recorded and characterized for the first time by the NMR method.

LITERATURE CITED

i. Yu. L. Kopaevich, G. G. BelenJkii, E. I. Mysov, and I. L. Knunyants, Zh. Vses. Khim. Obshch. im. D. I. Mendeleeva, 17, 236 (1972).

2. G.G. Belen'kii, E. P. Lur'e, and L. S. German, Izv. Akad. Nauk SSSR, Ser. Khim., 2728 (1975).

3. V.A. Petrov, G. G. Belen'kii, L. S. German, A. P. Kurbakova, and L. A. Leites, Izv. Akad. Nauk SSSR, Ser. Khim., 170 (1982).

4. R. West and P. T. Kwitowski, J. Am. Chem. Soc., 88, 5280 (1966). 5. R. D. Chambers, A. Parkin, and R. S. Matthews, J. Chem. Soc. Perkin Trans. i, 2106

(1976). 6. G.A. Olah and Y. K. Mo, Adv. Fluorine Chem., ~, 69 (1973). 7. B.E. Smart and G. S. Reddy, J. Am. Chem. Soc., 98, 5593 (1976). 8. G.A. Olah and R. J. Spear, J. Am. Chem. Soc., 97, 1539 (1975).

404

9. A. L. Henne, A. M. Whaley, and J. K. Stevenson, J. Am. Chem. Soc., 63, 3479 (1941). i0. V. V. Tyuleneva, A. A. Rozov, Yu. V. Zeifman, and I. L. Knunyants, Izv. Akad. Nauk

SSSR, Ser. Khim., 1136 (1975).

QUANTUM-CHEMICAL STUDY OF OPENING THE ETHYLENIM!NE

RING

L. M. Timofeeva and D. S. Zhuk UDC 530.145:541.124:542.92:547.415.3

Interest in the reactions of opening small heterocycles is mainly explained by the fact that the given reactions are the limiting step in the polymerization of these com- pounds [1-3] (the protonated ring is opened during chain growth and termination).

The synthesis of polyethylenimine (PEI) and its oligomers is of great practical interest and is being studied extensively in our laboratory [i, 4]. The polymerization of ethylenimine (EI) has an important characteristic, namely that in the liquid phase it al- ways proceeds stepwise under all conditions. The stepwise mechanism permits following the accumulation rate of the oligomers and making a parallel study of these reactions by quantum-chemical methods.

Previously it was experimentally shown in [4] that the protonated EI ring (EIH § is preferentially attacked by either the terminal or middle amino group of the growing chain via the "head-to-tail" principle. Due to the absence of a tail, the dimerization reaction proceeds via the "head-to-head" principle.

As a result, a quantum-chemical study of chain growth reduces to a calculation of the potentialenergy curves of the following reactions.

+ N \1 (i) / + \ / \

N . / + \

H2( ~)~N(CH~)~(NHCH~CH2)nN [

_ _ \I ~/ \H \l (2)

N ~ NH(CH~):~(NHCH~CH._,)nN ~ NH2(CH2)~N(CH~)~(NHCH2CH2)nN / \ l /\

CH~CH~NH.2 H CH-~CH~NH~

(3)

It is obvious that in reaction (2) the repeated attack by the primary amino group leads to a linear polymer. In reaction (3) branching in the chain is formed during attack by the secondary amino group~ If reaction (i) for the dimerization of (EI) can be studied directly, then for a quantum-chemical study of reactions (2) and (3) it is necessary to have models. Such models are EtNH2 and Et2NH, the use of which permits adequately describing the inter- action in the reaction center. Then a study of reactions (2) and (3) reduces to a calcula- tion of the potential energy curves of reactions (4) and (5) respectively.

H2 + N @- NH~CH2CH 3 ~ NH~(CH~).~NCH_CH 3 + Ho

(4)

A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 442-445, February, 1984. Original article submitted May 31, 1983.

0568-5230/84/3302-0405508.50 �9 1984 Plenum Publishing Corporation 405