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Aryl-substituted fluorophosphazenes VIII. 13C nuclear magnetic resonance parameters for phenyl-substituted fluorocyclotriphosphazenes
215
Journal of Organometallic Chemistry. 125 (1977) 215-218 0 Elsevier Sequoia S-A.. Lausanne - Printed in The Netherlands
ARYLSURSTITUTED
FLUOROPHOSPHAZENES
VIII *. 13C NUCLEAR MAGNETIC RESONANCE PARAMETERS PHENYL-SURSTITUTED FLUOROCYCLOTRIPHOSPHAZENES
CHRISTOPHER Department
FOR
W. ALLEN
of Chemistry.
(Received July 28th.
University
of Vermont,
Burlington.
Vermont
05401
(USA.)
19’76)
The 13C NMR spectra of the series of compounds P3N3F6_n(C6HS)n (n = 1,2, 4) are recorded and discussed. The par-u carbon chemical shift indicates that the phosphaxene ring exerts a moderate to strong electron withdrawing effect on the phenyl ring. Known correlations of 13Cchemical shifts with electron withdrawing parameters allow assignment of o* values for P3N3Fb_,,(C6HS),+ I &torn 0.42 (n = 4) to 0.74 (n = 1). Possible mechanisms for the perturbation of the phenyl ring are discussed. The phosphonrsl: arbon coupling constants to the C-2 (ortho) carbon are reMed to the nature of the substituents on the phosphorus atom in question.
Introduction There has been considerable interest in the interactions of organic centers of A electron density with Main Group elements in high formal oxidation states e.g. Si(IV) and P(V) [2,3]. Recently we reported the *H NMR spectra of a series of phenyl substituted fluorocyclotriphosphaxenes and concluded that the cycIotriphosphaxene moiety was a strong electron-withdrawing group with respect to the phenyl ring [4]. Unfortunately, ‘H chemical shifts are subject to a wide variety of shielding mechanisms and therefore a better probe of the electronic interactions in these is desirkble. Fluorinated monoaryl fluorocyclophosphazenes have been exam&d by igF NMR spectroscopy [5]. The results of this investigation ini compatible with the results of the *H NMR spectroscopic studies. However, the interpretation of i9F chemical shifts in fluoroaryl derivatives is a subject of some controwsy [S;?j. Since IjC NMR parametersare good probes to B ekctron density-in-aryl rings [8,9] and since there has been considerable recent i@res$ in ++‘.lC:I+I+fR @e&a of q~opboaphorus compounds [lO,lll, we .-
216
have chosen to investigate the 13C NMR spectra of a series of phenyl substituted
fluorocyclotriphosphaenes,
PSN,F6_,(C,H5),
(n = 1,2,4).
Experimental Ma teriak The phenyi-substituted fluorocyciotriphosphazenes fied by previousIy reported procedures [ 131.
were prepared and puri-
Mgasurements Natural abundance, proton noise-decoupled 13C NMR spectra were recorded at 22.63 MHz in the Fourier transform mode on a Bruker WH90 spectrophotometer equipped with a Nicolet 1080 computer_ Solution concentrations ranged from 0.5 to 3.8 mol% (approximately 9% by weight) in deuterochloroform. Shifts were measured from the solvent resonance and converted to a scale relative to benzene using the reported shift of benzene in chloroform [S].
The “C NMR spectra of the phenyl substituted fluorocyclotriphosphazenes typically show three doublets with decreasing splitting as one goes downfield. Thus the shifts of the carbon atoms ortho (C-2), meta (C-3) andpara (C-4) to the phosphazene moiety are easily assigned- These data are summarized in Table 1. The resonance due to C-l was only detected in PXN3F&H5. The low intensity of the C-l signal can be ascribed to lack of nuclear Overhauser enhancement and possibly to slow relaxation of the directly bonded phosphorus atom [ 131. The spectra of the cis and trans diphenyl derivatives, 1,3-P3N3F4(C6H5)2, show an additional line located within each of the C-2 and C-3 doublets. Since there is no reasonable assignment of these signals to the molecules in question, it is assumed that they arise from an impurity (possibly a phenoxy substituted cyclotriphosphazene). The concentrations of the solutions were chosen such that contributions to
TABLE1 OF
SELECTRD'3C~P~AM~~RS Compoud
ChcmiceI
C-25
P,Nsfs
d
cit-l.3-P3N3F4< tirzs-1.3-P~N~F4~C6Hs~ 1.l-P3N3F&%.H& 1.1.3.3-P$'hF1
0.6 O-4 0.4 0.4 -0.1
PHENYLFLWOROCYCLOTRIPHOSPHAZENES
shifts=
coupBnK
corlstaata
=
C-3
C-4
JW-G2)
JG+-C-3)
JCP-C-4
2.2 2-1 2_1 -20 2.1
5.8 5.2 5.1 4.2 29.
17.1 17.1 17.1 14.0 14.0
12.2 12.2 12.2 11.6 11.0
2.4 c
aPaNpumillionrrktivetobenrcne;Ood~rbihdo~tla.5. ... J(P--Cl)=142.4.=Linc~~~~~~uarc+o
-
2_4 2.4 =
, ~=~cIiZ-d01=-4.7iD~;.. ahdeo"sals' :
2.
._
217
the chemical shift due to solvent or high solute concentration were minimized [9,14]. In line with this expectation, variation in concentration did not produce any significant changes in the NMR parameters with the exception of a rare, random 1 Hz change in J(P-C-3) and J(P-C-2). Discussion Examination of the 13C chemical shifts for P3N3FSC6HS allows one to conclude that the phosphorus atom in this system exerts a strong perturbation on the phenyl ring. The 13C chemical shifts in substituted benzene rings have often been discussed in terms of substituent modification of the aryl n system [S]. In fact, the para carbon atom chemical shift in monosubstituted benzene derivatives has been successfully correlated to the total and a charge densities at the paru carbon atom (as calculated by the CND0/2 method) [9]. The P3NJFS and NO1 substituents give the same para carbon atom chemical shift so they may be assumed to perturb the aryl n system to a similar degree. The observation of a strong electron withdrawing effect of the P3N3FS function, as measured by 13C NMR, is in agreement with earlier 19F [5] and ‘H [4] measurements. The magnitude of this electron effect may be expressed by the (familiar) u* constants [15]. A value of u+ of approximately 0.74 can be obtained from a correlation of d vs. para carbon chemical shifts [ 91. The mechanism of the modification of the aryl K charge density is a more subtle problem 1161. Substituent effects which are manifested at the pam carbon atom are commonly ascribed to mesomeric interactions. However, the I% NMR parameters for P3N3F&HS are very similar to those observed for C6HSPOC12 [lo]. The mesomeric effects of phosphine oxides have been estimated to be low e.g. ug 2 0.07 which corresponds to a weak resonance acceptor 1171. Therefore, one should consider the possibility that coulombic effects (a inductive and field effects) play a significant role in these systems. The implication of coulombic effects in the “C NMR chemical shifts for other Group V aryl derivatives should be noted. On going from phosphines to phosphonium ions the pum carbon resonance is shifted approximately 7 ppm downfield [ll] and the pam carbon chemical shift in (C,HS)3SbBr,, a system where mesomeric effects would be expected to be minimal, is 4.3 ppm downfield from benzene [lS]. Further work on the nature of the electron withdrawing effect of the fluorophosphazene ring will be the subject of a future communication. In considering the entire series, P,N,F,_dC,H,), (n = 1,2,4), one can see a sharp drop in the electron withdrawing effect of the phosphazene ring as the electronegative fluorine atoms are replaced by phenyl groups. The para carbon atom chemical shifts range from +5.8 ppm (P&F&H,) to +2.9 ppm (1,1,3,3P,N,F,(C,H,).). The estimated d constants are as follows: 1,3-PSNJF,&~HS)1, 0.66; l,l-P&F&dH&, 0.57; 1,1,3,3-P,NSFz(CsHs),, 0.42. Thjs trend is consistent with either coulom@ic or mesomeric perturbation of the aryl7r system. The successl‘ve removal of fh&rine atoms dec reases the positive charge at the phosphorus Center hence less coulomhic effects; however, conco,tititiy the. phosphorus d ori&& wilI expand 1191, overkp v&h the small carbon orbitals will become less si@fi*t tid mesomeric interaction.will diminkh. In any case, sub+ution at a-@&ant ++__on the phosp&Gene”ring caii produce’signifi~t ;, .. :
218
-
changes in the pam carbon chemical shifts thus demonstrating the effective &insmission of electronic effects throughout the phosphazene ring. Similar conclusions have been drawn from consideration of phosphorus-phosphorus coupling constants in these compounds [ 201. The observation of essentially identical pam carbon chemical shifts in both cis- and tmns-1,3-P,N,F,(C,H& contrasts with the substantively different ‘H NMR shifts observed for the para protons in these compounds [4]. The difference in pam proton chemical shifts was ascribed to differing electronic effects between the two isomers but the *jC data clearly show this is not the case. The difference in ‘H shifts probably reflects a solvation phenomenon and demons&&es the difficulties in dealing with ‘H chemical shifts where a wide variety of shielding mechanisms are possible. The value of J(P-C-1) in P3N3F&H5 is quite high for aryl phosphorus derivatives but is comparable to the value observed for C6H5POC12 [lo]. The value of J(P-C-2) in the series of compounds under consideration fall into two groups i.e. a =PFC6H5 center has J(P-C-2) 2 1’7 Hz while a =P(C,H,), center exhibits a J(P-C-2) = 14 Hz. Similar behavior has been observed for J(PCCH) [4]. The origin of this effect could lie in 5%s character (smaller bond angle in a EP(C~H~)~ center) or in a greater positive charge in a =PF(C,H,) center. Whatever the causes, the magnitude of J(P-C-2) clearly has diagnostic value in structure assignment. Acknowledgement The experimental assistance of Mrs.. E. Richards of Oxford University in obtaining the 13Cspectra and the hospitality of Dr. H.A.O. Hill of Oxford University in providing laboratory space during a sabbatical leave are gratefully acknowledged. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
C.W.AUenapdP.L.Toch.J.Che~Soc.Ihlton.<1974)1685. C~.At~~.~ometnlChem-Rev,Sect.k5<1970)323. C.G.Pitt.J.Orgauometal.Chem..61<1970)49. C.W.AllenaudA.J.Qihite.Inor8.chtm.. 13<1974)1229. T.Chivasand N.L.Paddock.11<1972)848. W.AdcockmdBJ).Gu9Ln.J.Amu.Cbrm.Soe,97<1976)6871. J.FukunaaemdR.W.Taft.J. Amu.Chem.Soc,97 (1976~1612. J.B.Strothets.Caxbon-13NMRS pccttp3cogy. AcademkPren.NevYorir. 1972. G.LN&on.G.C.Lewmd J.D.Ch@olti. J.Amer.Chem.8oe..94<1972)3089. T-AAlbtUU.W-J.Free-rcdR.R.8chwefzer. J.Oq.Chan.. 40<1975)3487. G.kGm~.S~Crrrnermd&L.Mmi.J.~ChePlSoc.S8<1B76)2109. C-W-AllenandT.MoeIlu.~~Chem,7(1968~2177:C.~.M~n.~Y.TnnimdT.Moeller. ~~rk(me~.7<1968~2183;C.W.Wm~T.)Lbocllu.~o~S~.12(1970)293. EEreitmair,ELElSpohnmdS.Bager.~ew.Qtem. xzaenmt Edit, 14 <1975) 144. ~-ERakithJ.P.6mbman3LS.Wotshan. J.Oznno-Ghan.. 1~<1976)27C-G- Swain and EC. Luptua, J. Amer. Chem. So+. 90 (1968) 4328. A-R-~~~~mdR.D.Tooprom.~tw.Qcm.In~Edl+, 9~<197o)3i. J.M.-.wUeU. R2.C.Erownlec.A.R~~~. B.D.To9wmaadL.Yak?ioat&L&uariCbmn.' 6=-.91<1969~4500;T~.G.indlsl;EF-Jo~~f4_~~.&~.G_~-sthlmamr'md R.D.Toprom.AurtJ-Chem..28 <1976)551.
:.
19 ~~~,~~.L;;1y_y~J_~~~~~Ebcm;;~~.~i~,~,~4~.-: -’ - ‘..’ ;;‘; -: 19 K_A_R_luit&e&Qem;aarr.,8g(1g6g)~~7. --,_., _i_-::,___ .:.. ;.--'. i..-::-': . : _::-j 1 : .,.-: ,I. ..~ ._ 20 C-W-ARal+-~_~ _2~(1971~43s.'. .--, :“.-..> I__:_:;-':__=_-..-._-~ z.:...;: -;._._ ....r-...;.._ m_ : -::. __ _: __: ... _. ~. _1... : :_ : ....:-:: . _J :._ ~. -. -..
Journal of Organometallic Chemistry. 125 (1977) 215-218 0 Elsevier Sequoia S-A.. Lausanne - Printed in The Netherlands
ARYLSURSTITUTED
FLUOROPHOSPHAZENES
VIII *. 13C NUCLEAR MAGNETIC RESONANCE PARAMETERS PHENYL-SURSTITUTED FLUOROCYCLOTRIPHOSPHAZENES
CHRISTOPHER Department
FOR
W. ALLEN
of Chemistry.
(Received July 28th.
University
of Vermont,
Burlington.
Vermont
05401
(USA.)
19’76)
The 13C NMR spectra of the series of compounds P3N3F6_n(C6HS)n (n = 1,2, 4) are recorded and discussed. The par-u carbon chemical shift indicates that the phosphaxene ring exerts a moderate to strong electron withdrawing effect on the phenyl ring. Known correlations of 13Cchemical shifts with electron withdrawing parameters allow assignment of o* values for P3N3Fb_,,(C6HS),+ I &torn 0.42 (n = 4) to 0.74 (n = 1). Possible mechanisms for the perturbation of the phenyl ring are discussed. The phosphonrsl: arbon coupling constants to the C-2 (ortho) carbon are reMed to the nature of the substituents on the phosphorus atom in question.
Introduction There has been considerable interest in the interactions of organic centers of A electron density with Main Group elements in high formal oxidation states e.g. Si(IV) and P(V) [2,3]. Recently we reported the *H NMR spectra of a series of phenyl substituted fluorocyclotriphosphaxenes and concluded that the cycIotriphosphaxene moiety was a strong electron-withdrawing group with respect to the phenyl ring [4]. Unfortunately, ‘H chemical shifts are subject to a wide variety of shielding mechanisms and therefore a better probe of the electronic interactions in these is desirkble. Fluorinated monoaryl fluorocyclophosphazenes have been exam&d by igF NMR spectroscopy [5]. The results of this investigation ini compatible with the results of the *H NMR spectroscopic studies. However, the interpretation of i9F chemical shifts in fluoroaryl derivatives is a subject of some controwsy [S;?j. Since IjC NMR parametersare good probes to B ekctron density-in-aryl rings [8,9] and since there has been considerable recent i@res$ in ++‘.lC:I+I+fR @e&a of q~opboaphorus compounds [lO,lll, we .-
216
have chosen to investigate the 13C NMR spectra of a series of phenyl substituted
fluorocyclotriphosphaenes,
PSN,F6_,(C,H5),
(n = 1,2,4).
Experimental Ma teriak The phenyi-substituted fluorocyciotriphosphazenes fied by previousIy reported procedures [ 131.
were prepared and puri-
Mgasurements Natural abundance, proton noise-decoupled 13C NMR spectra were recorded at 22.63 MHz in the Fourier transform mode on a Bruker WH90 spectrophotometer equipped with a Nicolet 1080 computer_ Solution concentrations ranged from 0.5 to 3.8 mol% (approximately 9% by weight) in deuterochloroform. Shifts were measured from the solvent resonance and converted to a scale relative to benzene using the reported shift of benzene in chloroform [S].
The “C NMR spectra of the phenyl substituted fluorocyclotriphosphazenes typically show three doublets with decreasing splitting as one goes downfield. Thus the shifts of the carbon atoms ortho (C-2), meta (C-3) andpara (C-4) to the phosphazene moiety are easily assigned- These data are summarized in Table 1. The resonance due to C-l was only detected in PXN3F&H5. The low intensity of the C-l signal can be ascribed to lack of nuclear Overhauser enhancement and possibly to slow relaxation of the directly bonded phosphorus atom [ 131. The spectra of the cis and trans diphenyl derivatives, 1,3-P3N3F4(C6H5)2, show an additional line located within each of the C-2 and C-3 doublets. Since there is no reasonable assignment of these signals to the molecules in question, it is assumed that they arise from an impurity (possibly a phenoxy substituted cyclotriphosphazene). The concentrations of the solutions were chosen such that contributions to
TABLE1 OF
SELECTRD'3C~P~AM~~RS Compoud
ChcmiceI
C-25
P,Nsfs
d
cit-l.3-P3N3F4< tirzs-1.3-P~N~F4~C6Hs~ 1.l-P3N3F&%.H& 1.1.3.3-P$'hF1
0.6 O-4 0.4 0.4 -0.1
PHENYLFLWOROCYCLOTRIPHOSPHAZENES
shifts=
coupBnK
corlstaata
=
C-3
C-4
JW-G2)
JG+-C-3)
JCP-C-4
2.2 2-1 2_1 -20 2.1
5.8 5.2 5.1 4.2 29.
17.1 17.1 17.1 14.0 14.0
12.2 12.2 12.2 11.6 11.0
2.4 c
aPaNpumillionrrktivetobenrcne;Ood~rbihdo~tla.5. ... J(P--Cl)=142.4.=Linc~~~~~~uarc+o
-
2_4 2.4 =
, ~=~cIiZ-d01=-4.7iD~;.. ahdeo"sals' :
2.
._
217
the chemical shift due to solvent or high solute concentration were minimized [9,14]. In line with this expectation, variation in concentration did not produce any significant changes in the NMR parameters with the exception of a rare, random 1 Hz change in J(P-C-3) and J(P-C-2). Discussion Examination of the 13C chemical shifts for P3N3FSC6HS allows one to conclude that the phosphorus atom in this system exerts a strong perturbation on the phenyl ring. The 13C chemical shifts in substituted benzene rings have often been discussed in terms of substituent modification of the aryl n system [S]. In fact, the para carbon atom chemical shift in monosubstituted benzene derivatives has been successfully correlated to the total and a charge densities at the paru carbon atom (as calculated by the CND0/2 method) [9]. The P3NJFS and NO1 substituents give the same para carbon atom chemical shift so they may be assumed to perturb the aryl n system to a similar degree. The observation of a strong electron withdrawing effect of the P3N3FS function, as measured by 13C NMR, is in agreement with earlier 19F [5] and ‘H [4] measurements. The magnitude of this electron effect may be expressed by the (familiar) u* constants [15]. A value of u+ of approximately 0.74 can be obtained from a correlation of d vs. para carbon chemical shifts [ 91. The mechanism of the modification of the aryl K charge density is a more subtle problem 1161. Substituent effects which are manifested at the pam carbon atom are commonly ascribed to mesomeric interactions. However, the I% NMR parameters for P3N3F&HS are very similar to those observed for C6HSPOC12 [lo]. The mesomeric effects of phosphine oxides have been estimated to be low e.g. ug 2 0.07 which corresponds to a weak resonance acceptor 1171. Therefore, one should consider the possibility that coulombic effects (a inductive and field effects) play a significant role in these systems. The implication of coulombic effects in the “C NMR chemical shifts for other Group V aryl derivatives should be noted. On going from phosphines to phosphonium ions the pum carbon resonance is shifted approximately 7 ppm downfield [ll] and the pam carbon chemical shift in (C,HS)3SbBr,, a system where mesomeric effects would be expected to be minimal, is 4.3 ppm downfield from benzene [lS]. Further work on the nature of the electron withdrawing effect of the fluorophosphazene ring will be the subject of a future communication. In considering the entire series, P,N,F,_dC,H,), (n = 1,2,4), one can see a sharp drop in the electron withdrawing effect of the phosphazene ring as the electronegative fluorine atoms are replaced by phenyl groups. The para carbon atom chemical shifts range from +5.8 ppm (P&F&H,) to +2.9 ppm (1,1,3,3P,N,F,(C,H,).). The estimated d constants are as follows: 1,3-PSNJF,&~HS)1, 0.66; l,l-P&F&dH&, 0.57; 1,1,3,3-P,NSFz(CsHs),, 0.42. Thjs trend is consistent with either coulom@ic or mesomeric perturbation of the aryl7r system. The successl‘ve removal of fh&rine atoms dec reases the positive charge at the phosphorus Center hence less coulomhic effects; however, conco,tititiy the. phosphorus d ori&& wilI expand 1191, overkp v&h the small carbon orbitals will become less si@fi*t tid mesomeric interaction.will diminkh. In any case, sub+ution at a-@&ant ++__on the phosp&Gene”ring caii produce’signifi~t ;, .. :
218
-
changes in the pam carbon chemical shifts thus demonstrating the effective &insmission of electronic effects throughout the phosphazene ring. Similar conclusions have been drawn from consideration of phosphorus-phosphorus coupling constants in these compounds [ 201. The observation of essentially identical pam carbon chemical shifts in both cis- and tmns-1,3-P,N,F,(C,H& contrasts with the substantively different ‘H NMR shifts observed for the para protons in these compounds [4]. The difference in pam proton chemical shifts was ascribed to differing electronic effects between the two isomers but the *jC data clearly show this is not the case. The difference in ‘H shifts probably reflects a solvation phenomenon and demons&&es the difficulties in dealing with ‘H chemical shifts where a wide variety of shielding mechanisms are possible. The value of J(P-C-1) in P3N3F&H5 is quite high for aryl phosphorus derivatives but is comparable to the value observed for C6H5POC12 [lo]. The value of J(P-C-2) in the series of compounds under consideration fall into two groups i.e. a =PFC6H5 center has J(P-C-2) 2 1’7 Hz while a =P(C,H,), center exhibits a J(P-C-2) = 14 Hz. Similar behavior has been observed for J(PCCH) [4]. The origin of this effect could lie in 5%s character (smaller bond angle in a EP(C~H~)~ center) or in a greater positive charge in a =PF(C,H,) center. Whatever the causes, the magnitude of J(P-C-2) clearly has diagnostic value in structure assignment. Acknowledgement The experimental assistance of Mrs.. E. Richards of Oxford University in obtaining the 13Cspectra and the hospitality of Dr. H.A.O. Hill of Oxford University in providing laboratory space during a sabbatical leave are gratefully acknowledged. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
C.W.AUenapdP.L.Toch.J.Che~Soc.Ihlton.<1974)1685. C~.At~~.~ometnlChem-Rev,Sect.k5<1970)323. C.G.Pitt.J.Orgauometal.Chem..61<1970)49. C.W.AllenaudA.J.Qihite.Inor8.chtm.. 13<1974)1229. T.Chivasand N.L.Paddock.11<1972)848. W.AdcockmdBJ).Gu9Ln.J.Amu.Cbrm.Soe,97<1976)6871. J.FukunaaemdR.W.Taft.J. Amu.Chem.Soc,97 (1976~1612. J.B.Strothets.Caxbon-13NMRS pccttp3cogy. AcademkPren.NevYorir. 1972. G.LN&on.G.C.Lewmd J.D.Ch@olti. J.Amer.Chem.8oe..94<1972)3089. T-AAlbtUU.W-J.Free-rcdR.R.8chwefzer. J.Oq.Chan.. 40<1975)3487. G.kGm~.S~Crrrnermd&L.Mmi.J.~ChePlSoc.S8<1B76)2109. C-W-AllenandT.MoeIlu.~~Chem,7(1968~2177:C.~.M~n.~Y.TnnimdT.Moeller. ~~rk(me~.7<1968~2183;C.W.Wm~T.)Lbocllu.~o~S~.12(1970)293. EEreitmair,ELElSpohnmdS.Bager.~ew.Qtem. xzaenmt Edit, 14 <1975) 144. ~-ERakithJ.P.6mbman3LS.Wotshan. J.Oznno-Ghan.. 1~<1976)27C-G- Swain and EC. Luptua, J. Amer. Chem. So+. 90 (1968) 4328. A-R-~~~~mdR.D.Tooprom.~tw.Qcm.In~Edl+, 9~<197o)3i. J.M.-.wUeU. R2.C.Erownlec.A.R~~~. B.D.To9wmaadL.Yak?ioat&L&uariCbmn.' 6=-.91<1969~4500;T~.G.indlsl;EF-Jo~~f4_~~.&~.G_~-sthlmamr'md R.D.Toprom.AurtJ-Chem..28 <1976)551.
:.
19 ~~~,~~.L;;1y_y~J_~~~~~Ebcm;;~~.~i~,~,~4~.-: -’ - ‘..’ ;;‘; -: 19 K_A_R_luit&e&Qem;aarr.,8g(1g6g)~~7. --,_., _i_-::,___ .:.. ;.--'. i..-::-': . : _::-j 1 : .,.-: ,I. ..~ ._ 20 C-W-ARal+-~_~ _2~(1971~43s.'. .--, :“.-..> I__:_:;-':__=_-..-._-~ z.:...;: -;._._ ....r-...;.._ m_ : -::. __ _: __: ... _. ~. _1... : :_ : ....:-:: . _J :._ ~. -. -..