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Paramagnetic shifts induced by europium and praseodymium chelates in the NMR spectrum of bisphenol a diglycidyl ether.

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Die Angewandte Makromolekulare Chemie 27 ( 1 9 7 2 ) 159-164 ( N r . 3 8 1 )
From the Research Department, CIBA-GEIGY (UK) LTD., Plastics Division
Duxford, Cambridge CB 2 4 &A, England
Paramagnetic Shifts Induced by Europium and
Praseodymium Chelates in the NMR Spectrum of
Bisphenol A Diglycidyl Ether
By JAMES
FREDERICK
CHANDLERand BERNARD
PETER
STARK
(Eingegangen am 7 . April 1972)
SUMMARY:
A preliminary study has been made of the effects of the shift reagents Eu (DPM)z
and Pr (DPM)s on the NMR spectrum of Bisphenol A diglycidyl ether (I).Protons
attached to the epoxy ring were observed to shift appreciably more than protons of
the exocyclic -0CHzgroup, on addition of these chelates. The shifts could be
reversed by addition of an alcohol, which interacted preferentially with the shift
reagent.
ZUSAMMENFASSUNG:
Es wurde eine Voruntersuchung des Einflusses unternommen, den die Verschiebereagenzien Tris-(dipivaloylmethano)-europium uncl Tris-(dipivaloy1methano)-praseodym auf das NMR-Spektrum des Diglyzidylithers des Bisphenol A ausuben. Es
ergab sich, da13 die Signale der am Epoxidring anliegenden Protonen durch den Zusatz dieser Chelate weit mehr als die Signale der exozyklischen -0CHz-Gruppen
verschoben werden. Die Verschiebung kann man durch den Zusatz eines Alkohols
ruckgangig machen, der vorzugsweise mit dem Verschiebemittel reagiert.
Introduction
A study1 has recently been made of t h e effects produced by tris(dipiva1omethanato)europium [Eu (DPM)3] and tris(dipiva1omethanato)praseodymium
[Pr (DPM)3]on the NMR spectra of some phenolic resin derivatives containing
two or more M e r e n t co-ordination sites available for interaction with the
lanthanide chelates. The present paper reports our preliminary investigations
of the effects of Eu (DPM)3and Pr (DPM)3on t h e NMR spectrum of Bisphenol
A diglycidyl ether (I),which is a major component of many epoxy resins of
commercial a n d technical importance. The diepoxide (I)contains two different
types of co-ordination site : t h e epoxy-oxygen atom, and the ether-oxygen atom
of the glycidyl group :
159
J. F. CHANDLERand B. P. STARK
The NMR spectra of compounds containing the glycidyl group generally
contain patterns of ABCDE type, the five protons usually appearing as three
sets of multiplets-corresponding (in order of increasing chemical shift, 6) to:
HA HB; He; HD HE. With aromatic glycidyl ethers, three reasonably
well separated multiplets can generally be observed, centred a t 6 values of ca.
2.7, 3.2 and 4.0 ppm. For many epoxides, JABis within the range 4.6-6.7
Hz2-5, whereas the trans-coupling across the epoxy ring (JAc)is often in the
range 2.0-2.9 Hz3-13, but can be as high as 3.2 Hz14-15 and as low as 0.5 Hzl6.
Cis-coupling ( JBC)
in epoxides is generally3-89 10-14117 of the order of 3.5-4.9
Hz, but can be as small as 2.2 Hz9. With epoxides containing the glycidyl group,
the magnitude of the coupling constant JDEof the geminal protons of the
exocyclic methylene link is usually about 10.6-12.9 Hz2-6118, and JCD
and
J D E are likely t o be in the region of 3-4 Hz and 5-7 H z 2 - 5 9 6 .
+
+
Apart from the signals due to the ten protons of the two glycidyl ether groups,
the NMR spectrum (cf. Fig. 1) of Bisphenol A diglycidyl ether contains an
AA'BB' pattern due t o the eight aromatic protons (labelled Ho, H, in formula
I)),centred a t 6 M 6.9, and a singlet a t 6 rn 1.6, attributable to the six protons
of the central gem.-dimethyl group.
10
Fig. 1.
160
8
6
4
NMR spectrum of Bisphenol A diglycidyl ether.
2
0
6
N M R Spectrum of Bisphenol A Diglycidyl Ether
Results and Discussion
I n the present work, additions of Eu(DPM)3 to a solution of diepoxide (I)in
carbon tetrachloride brought about considerable changes in the NMR spectrum
(cf. Fig. 2 (a)-(f)). The most striking feature was the large downfield shift
produced in the resonances of the epoxy protons; the signals for HA and H B
moved rapidly through the multiplets due t o H c and H D HE. On increasing
the ratio of Eu(DPM)sto (I), the H A H Bmultiplet continuedtomoverapidly
downfield, followed by the signal for H c ; the HD HE resonances also moved
downfield, but less rapidly. At the same time, the aromatic pattern collapsed t o
a singlet, and then inverted t o form a pair of doublets (complexing of the etheroxygen atom causing the aromatic protons ortho to the oxygen function to shift
downfield more rapidly than the H, protons). The chemical shifts of the protons
of the gem.-dimethyl group wcre hardly affected by addition of the complex.
The addition of Eu(DPM)3 was terminated when the separate peaks became
broadened significantly, and the individual patterns less well defined ; at this
stage (Fig. 2 (f)), the signals furthest downfield were those of H A HB, (ca.
6 13.8), H c lying a little upfield (ca. 6 13.1). Further upfield (ca. 6 9.9) was a
double peak (HD HE), then the aromatic pattern (which was essentially a
widely-separated pair of doublets), and finally the gem.-dimethyl signal. The
shifts induced in the resonances of the five protons of epichlorohydrin by
Eu (DPM)s were on the whole similar t o shifts produced in those of the analogous protons of diepoxide (I).
As expected, analogous upfield NMR shifts were observed on addition of
Pr(DPM)3 to a solution of the diepoxide (I)in carbon tetrachloride (cf. Fig. 3
(a)-(c)). The pattern of the epoxy protons HA Hg moved very rapidly
upfield (through the gem.-dimethyl and TMS signals), closely followed by the
H E multiplet. As expected, the
H c pattern and, less rapidly, by the H D
aromatic pattern did not invert in this case, but increasing separation of the
component resonances (doublets) was observed.
It was interesting t o note that these spectral changes could be reversed progressively by addition of an alcohol (tert.-butanol was used in the present work)
to the solution of epoxide plus shift reagent (cf. Fig. 4 (a)-(c)). It was evident
that the alcohol complexed preferentially with the chelate, displacing it from
the epoxy- and ether-oxygen atoms. If sufficient tert.-butanol was added, the
spectrum then recorded was very similar to that obtained for the original diepoxide (I)alone, in carbon tetrachloride solution*.
The results described above clearly indicate that Eu(DPM)3 and P r (DPM)3
interact more strongly with the oxygen atom of an epoxy group than with the
+
+
+
+
+
+
+
* Except,
of course, for the extra peaks due to the added tert. butanol and the
shift reagents.
161
J. F. CHANDLERand R. P. STARK
0
a
I
20
I
I
18
16
8
Fig. 3.
162
14
12
A
I
I
10
8
I
I
I
I
G
4
2
06
NMR spectra of the system Bisphenol A diglycidyl ether in CClr-solution
with an increasing amount of Eu (DPM)3((a)- (f)).
Fig. 2 .
10
I
6
4
2
0
-2
-4
-6
-8
-106
NMR spectra of the system Bisphenol A diglycidyl ether in CC14-solution
with an increasing amount of Pr(DPM)3 ((a)- (c)).
N M R Spectrum of Bisphenol A Diglycidyl Ether
8
10
G
4
2
0
-2
-4
-6
-8
-106
Fig. 4. N M R spectra of the system Bisphenol A diglycidyl ether and Pr (DPM)3in
CC14-solution with an increasing amount of tert.-butanol ((a)- (c)).
exocyclic glycidyl ether oxygen atom ; alcohols complex considerably more
powerfully than either, however**. Recent papers have described work which
demonstrates that the epoxy oxygen atoms of endrinzo, dieldrin20 and photodieldrin20, and of an epoxide derived from cyclo-octatetraene dimer, also
complex strongly with europium chelates. The present note is the first, it is
believed, to be concerned with an epoxide containing a competing coordination
site.
A further interesting effect was noted when the amount of solvent (carbon
tetrachloride) was varied while the ratio of chelate to diepoxide (I)was kept
constant: small but significant changes occurred in the positions of certain of the
NMR bands - especially those peaks corresponding to the five protons of the
glycidyl group. The results in Table 1 below exemplify the effect of increasing
the dilution of the NMR solution a t a fixed solute ratio of Pr (DPM)3:(I); a
similar phenomenon was noted with Eu(DPM)3 (I) increasing amounts of
+ +
cc14.
Experimental
N M R spectra were recorded at 30°C in cc14, using a Perkin-Elmer R-12 (6OMHz)
spectrometer, with tetramethylsilane as internal standard. The Eu and Pr chelates
were prepared as indicated previously22.
for valuable technical assistance, in
We are grateful t o Mr. A. J. FRENCH
obtaining numerous NMR spectra.
**
A recent paper19 indicates that, in a molecule containing an ester group and a
hydroxy group, initially complexing occurs almost entirely at the -OH group.
163
J. F. CHANDLERand B. P. STARK
Table 1. Position of NMR bands of the system Bisphenol A diglycidyl ether
Pr (DPM)3 increasing amounts of solvent (CC14).
+
.
(I)*
(g)
Pr (DPM)3
(g)
0.216
0.216
0.216
0.216
0.216
0
0.153
0.153
0.153
0.153
*
Grams of
solute per
kgsolution
+
Chemical shifts ( 6 ) of NMR bands
of protons
373
155
80
61
I
H A B Hc
2.6
-1.0
-0.6
-0.2
0.0
3.2
-0.3
0.0
0.4
0.6
I HDEI
H,
3.95
1.8
2.2
2.3
2.4
6.7
5.9
6.0
6.1
6.1
I
Hm
7.1
6.7
6.8
6.8
6.8
Mole ratio of (I)to Pr(DPM)3 = 2.814: 1.
R. ANDERSON,
A. H. HAINES,B. P. STARK,Anzew. Makromol. Chem. 26 (1972)
171; 27 (1972) 151.
J. R. BACON
and M. 3 . COLLIS,
Chem. Ind. (London) 1971,930.
W. A. THOMAS,
J. Chem. SOC.B 1968, 1187.
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Applied Spectrosc. 22 (1968) 773.
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and V. U. NAYAR,
Indian J..Pure Appl. Phys. 4 (1966) 361.
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J. Chem. Phys. 33 (1961) 1522.
P. E. WEI and P. E. BUTLER,
J. Polymer Sci. A-1 6 (1968) 2461.
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and M. FISHMAN,
J. Org. Chem. 34 (1969) 4060.
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and J. D. SWALEN,
J. Chem. Phys. 32 (1960) 1378.
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J. Chem. Phys. 34 (1962) 980.
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S. MEIBOOM,
and L. C. SNYDER,
J. Amer. Chem. SOC.90 (1968)
2183.
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D. J. BLEARS,
and K. H. WEBB,J. Chem. SOC.1965,810.
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and D. D. CARMELITE,J. Amer. Chem. SOC.88 (1966) 4039.
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and H. DE LUZE,Bull. SOC.Chim. Fr. 1968, 2169.
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M. WITANOWSKI,
and T. URBANSKI,
J. Org. Chem. 32 (1967)
4050.
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J. Org. Chem. 31 (1966) 3921.
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and S. K. KUNDU,
J. Org. Chem. 34 (1969) 1532.
l* J. L. PIERRE
and P. ARNAUD,
Bull. SOC.Chim. Fr. 1969, 2868.
1 9 I. FLEMING,
S. W. HANSON,
and J. K . M. SANDERS,
Tetrahedron Lett. 1971,3733.
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and R. E. SIEVERS,
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1
164
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paramagnetic, nmr, europium, induced, spectrum, ethers, bisphenol, praseodymium, shifts, chelate, diglycidyl
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