NMR spectra of cyclic formals formed during the early stage of the copolymerization of trioxane and ethylene oxide

Article abstract of DOI:10.1366/0003702001950580

During the early stage of the copolymerization of trioxane and ethylene oxide, we found the formation of three novel cyclic compounds: 1,3,5,7-tetraoxacyclononane (TOCN), 1,3,5,7,10-pentaoxacyclododecane (POCD), and 1,3,5,7,10,13-hexaoxacyclopentadecane (

Full text of DOI:10.1366/0003702001950580

NMR Spectra of Cyclic Formals Formed During the Early
Stage of the Copolymerization of Trioxane and
Ethylene Oxide
NAOAKI YAMASAKI, JUNZO MASAMOTO,* and KENJI KANAORI
-
Department of Polymer Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo ku, Kyoto 606 8585 Japan
-
-
(J.M., K.K.); and Functional Additives Technology Department One, Asahi Chemical Industry Co., Ltd. 6 2700, Asahi machi,
-
-
Nobeoka 882 0847 Japan (N.Y.)
-
-
-
During the early stage of the copolymerization of trioxane and eth
ylene oxide, we found the formation of three novel cyclic com
-
1), and from 1,3,5 trioxepane, 1,3 dioxolane was formed
-
(reaction 1).
It is already known that the commercial acetal copol
-
-
pounds: 1,3,5,7 tetraoxacyclononane (TOCN), 1,3,5,7,10 pentaoxa
-
-
cyclododecane (POCD), and 1,3,5,7,10,13 hexaoxacyclopentadecane
(HOCP). These novel cyclic compounds were new direct reaction
products of 1 mole of trioxane and 1 mole of ethylene oxide, 1 mole
ymer from trioxane and ethylene oxide has a certain kind
of ethylene oxide sequence, that is, one ethylene oxide
sequence, two consecutive ethylene oxide sequences, and
-
three consecutive ethylene oxide sequences. It was pos
tulated that one ethylene oxide sequence will come from
of trioxane and 2 moles of ethylene oxide, and 1 mole of trioxane
1
-
H
and 3 moles of ethylene oxide, respectively. We compared the
13
-
NMR and C NMR spectra of each cyclic compound and precisely
-
the copolymerization of trioxane with 1,3 dioxolane and
1,3 trioxepane, two consecutive ethylene oxide sequences
-
assigned the signals of each spectrum using NOESY (nuclear Ov
-
erhauser enhancement spectroscopy) and HETCOR (heteronuclear
1
-
correlated spectroscopy). We also compared the H NMR spectra
of POCD and HOCP with the corresponding cyclic formals with
will come from the copolymerization of trioxane with
POCD, and three consecutive ethylene oxide sequences
will come from the copolymerization of trioxane with
-
one oxymethylene unit, diethylene glycol formal (DEGF) and trie
thylene glycol formal (TEGF). Interestingly, we found that DEGF
1
13
-
-
HOCP. We then compared the H NMR and C NMR
spectra of these three novel cyclic formals (TOCN,
POCD, and HOCP), which were obtained as the reaction
products of the copolymerization of trioxane and ethylene
oxide, and precisely assigned each spectrum using NOESY
(nuclear Overhauser and enhancement spectroscopy) and
HETCOR (heteronuclear correlated spectroscopy).
-
and TEGF, which have only one oxymethylene unit, showed no pro
ton splitting of the oxyethylene units, while POCD and HOCP,
which have three consecutive oxymethylene units, have split signals
for the oxyethylene units.
1
13
-
-
Index Headings: H NMR spectra; C NMR spectra; Cyclic formals.
-
TOCN, POCD, and HOCP have three consecutive ox
ymethylene units, while diethylene glycol formal (DEGF)
INTRODUCTION
-
and triethylene glycol formal (TEGF) have only one ox
ymethylene unit (see Fig. 1). We compared the NMR
spectra of these compounds and found an interesting phe
Polyacetal resin, which is a representative engineering
plastic, is produced by the polymerization of formaldehyde
(acetal homopolymer) or the copolymerization of trioxane
-
-
ymer). There are few reports on the polymerization of
nomenon with respect to differences in the splitting of
the oxyethylene unit.
with a cyclic ether such as ethylene oxide (acetal copol
formaldehyde;1±7 on the other hand, there have been nu
merous reports on the polymerization of trioxane. How
-
-
-
ever, these studies academically deal mainly with the co
-
EXPERIMENTAL
polymerization of trioxane with 1,3 dioxolane. In spite of
the importance of the copolymerization of trioxane with
Material. Each materialÐ TOCN, POCD, and
HOCPÐ was obtained as the reaction product of trioxane
and ethylene oxide. The reaction was done as follows. In
a 100 mL glass ¯ ask, 65 g (0.72 mol) of trioxane was
melted at 70 8C under an N2 atmosphere and stirred with
a magnetic stirrer. Gaseous ethylene oxide (3.9 mol % to
trioxane) was absorbed by trioxane, and the cyclohexane
-
ethylene oxide, which is presently produced on an indus
trial basis, the number of reports are relatively few.8±13
We found a direct reaction between trioxane and eth
-
-
ylene oxide, which was reported to be impossible by sev
eral authors,9,13 during our studies on the copolymeriza
tion of trioxane and ethylene oxide, and we found several
novel compounds. We then determined each compound
-
solution of BF3´OBu2 (3.9 3 1025 mol/mol trioxane;
-
BF3´OBu2 was diluted 50 times by cyclohexane) was in
-
jected into the reaction mixture with a microsyringe, and
-
to be 1,3,5,7 tetraoxacyclononane (TOCN) (reaction 1),
1,3,5,7,10 pentaoxacyclododecane (POCD) (reaction 2)
-
-
then the reaction proceeded at 70 8C. The reaction mix
ture was in a homogeneous state before the beginning of
the polymerization. The reaction mixture with a homo
geneous state was withdrawn (20 g) by a syringe at def
inite times (15 min, 20 min, and 25 min after the injection
-
of BF3´OBu2), poured into an n PrOH solution of NaOH
(0.1 wt % NaOH in n propanol, 50 mL), and the reaction
-
-
and 1,3,5,7,10,13 hexacyclopentadecane (HOCP) (reac
tion 3), respectively (see Scheme I). We also determined
-
-
-
that from TOCN, 1,3,5 trioxepane was formed (reaction
Received 1 June 1999; accepted 7 March 2000.
* Author to whom correspondence should be sent. Present address:
- -
Dept. of Management Science, Fukui University of Technology, 3 6
-
-
1, Gakuen, Fukui shi, 910 8505 Japan.
-
was stopped. The formation yield of each material for the
-
0003 7028 / 00 / 5407 1069$2.00 / 0
-
Volume 54, Number 7, 2000
APPLIED SPECTROSCOPY
1069
q 2000 Society for Applied Spectroscopy

SCHEME I. Reaction scheme.
initial ethylene oxide was as follows: TOCN, 48%;
POCD, 20%; HOCP, 15%. The reaction products were
-
®rst separated by microdistillation (TOCN showed a boil
ing point of 180 8C at 760 torr, while POCD showed a
boiling point of 182 8C at 4 torr, and HOCP showed a
boiling point of 212 8C at 4 torr), and ®nally separated
and collected by preparative gas chromatography using a
packed column (4.0 mm diameter, 2 m length, packing
agent: Chromosorb W containing 10% liquid silicone
-
OV 17) at a column temperature of 150 8C.
For the con®rmation of each cyclic formal, the mass
-
spectra were checked. The electron impact mass spec
trometry (El MS) of TOCN showed a molecular ion peak
of 134 and composition formula of C5H10O4, which is in
accordance with the molecular weight and composition
FIG. 1. Notation of each proton and carbon of TOCN, POCD, HOCP,
DEGF, and TEGF.
-
formula of TOCN. The El MS of POCD showed a mo
lecular ion peak of 177 and the composition formula of
C7H14O5, which is in accordance with the compound of
13
-
and C NMR measurements, and CDCl3 was used for
-
a one proton elimination of POCD (molecular weight:
178; composition formula: C7H15O5). The chemical ion
the solvent. About 20 mg of each sample was dissolved
in 0.7 mL CDCl3. The NOESY and HETCOR spectra
were measured for the precise assignment of each signal.
The spectrometer settings were as follows: For the NOESY
-
ization mass spectrometry (Cl MS) of HOCP showed a
molecular ion peak of 223, which is in accordance with
-
the compound of a one proton attachment of HOCP (mo
lecular weight: 222).
-
-
measurement, pulse width, 11.5 ms; delays, 1.134 s; spec
tral widths, 700 Hz for both dimensions; number of time
domain points, 256 (td 2) 3 128 (td 1); mixing time, 200
ms; data size, 512 (f2) 3 512 (f1); window function, sine
bell. For the HETCOR measurement, pulse widths, 11.6
The observed elemental analyses of each formal are in
accordance with the theoretical values: TOCN (Found:
C, 44.76; H, 7.75. Calc.: C, 44.78; H, 7.50%), POCD
(Found: C, 47.25; H, 8.06. Calc.: C, 47.19; H, 7.87%),
HOCP (Found: C, 48.35; H, 8.00. Calc.: C, 48.65; H,
8.11%).
ms for 13C and 11.0 ms for H; delays, 1.170 s; spectral
1
widths, 3100.7 Hz for 13C and 700 Hz for H; number of
1
time domain points, 1024 (td 2) 3 256 (td 1); data size:
1024 (f2) 3 512 (f1); window function, sine bell.
DEGF was synthesized from diethylene glycol (0.2
mol) and paraformaldehyde (0.2 mol) catalyzed by 0.5
wt % pyrophosphoric acid in the presence of heptane
(boiling point 98.4 8C 20 wt % of the reactant) immersed
in an oil bath controlled at 130 8C with re¯ uxing heptane
RESULTS AND DISCUSSION
-
To make the discussion clear, the notation of each pro
ton and carbon atom of TOCN, POCD, and HOCP is
shown in Fig. 1 as Ha, Hb, Hc, Hd, and He for each proton,
and Ca, Cb, Cc, Cd and Ce for each carbon.
NMR Spectra of TOCN. The H and C NMR spec
tra of TOCN are summarized in Tables I and II, respec
-
in the reaction zone, while the generated water was with
drawn. After generation of the water stopped, DEGF was
distilled under the reduced pressure of 30 torr at 60 8C
(yield: 81% of the initial diethylene glycol). DEGF was
redistilled for puri®cation. A similar procedure was done
1
13
-
-
-
-
-
1
-
tively. In the H NMR spectrum, three singlets were ob
-
lene glycol), and puri®ed TEGF was obtained (30 torr,
for the synthesis of TEGF (yield: 63% of initial triethy
served at 5.05, 4.93, and 3.85 ppm, and its area ratio was
1:2:2. From the signal strength, 5.05 ppm was attributed
to Ha, 4.93 ppm was attributed to Hb, and 3.85 ppm was
attributed to Hc. From the viewpoint of chemical bonding,
the carbon atom, which is connected to Ha, is surrounded
78 8C)
-
Analysis. A 400 MHz NMR (JEOL JNM AL 400 FT
1
-
NMR system spectrometer) was used for the H NMR
1070 Volume 54, Number 7, 2000

1
13
-
-
C NMR chemical shift assignment (ppm) of TOCN,
TABLE I. H NMR chemical shift assignment of TOCN, POCD,
TABLE II.
HOCP, DEGF, and TEGF.a
POCD, and HOCP.a
Ha
Hb
Hc
Hd
He
Ca
Cb
Cc
Cd
Ce
TOCN
POCD
HOCP
DEGF
TEGF
5.05
s, 2H
5.05,
s, 2H
5.08,
s, 2H
4.90
s, 2H
4.79
s, 2H
4.93
s, 4H
4.90
s, 4H
4.92,
s, 4H
3.81,
s, 8H
3.83,
s, 8H
3.85
s, 4H
3.83±3.85,
m, 4H
3.75±3.79,
m, 4H
TOCN
POCD
HOCP
96.9
95.1
91.3
97.1
95.9
93.2
70.5
68.7
66.5
70.6
70.7
3.73±3.75,
m, 4H
3.68±3.73,
m, 4H
70.4
a
Unit is ppm.
3.66,
s, 4H
result is shown in Fig. 4. Carbon atoms of the formal
were assigned similarly to that of TOCN; a signal of 95.1
ppm was assigned to C , and that of 95.9 ppm was as
signed to Cb. As for the oxyethylene, the signal of 70.6
3.69
s, 4H
a
-
a
Unit is ppm. Characters s and m indicate singlet and multiplet signals,
respectively.
13
-
ppm of C makes the cross peak of the proton of oxy
ethylene occur at high magnetic ®eld (3.73±3.75 ppm),
and the signal of 68.7 ppm makes the cross peak of the
proton occur at low magnetic ®eld (3.83±3.85 ppm). Thus
the symmetrical multiplet signals of 1H of oxyethylene
were found to be connected to the different carbon atoms.
To assign the Hc and Hd, that is to say, to con®rm
with two ±OCH2O units, and the carbon atom, which is
connected to Hb, is connected to one side by ±OCH2, and
to the other side by ±OCH2CH2. Thus, considering the
-
electron attractivity of the oxygen atom, the electron den
sity of Ha was thought to be lower than that of Hb, and
this order was in accordance with that of the chemical
shift. On the other hand, with respect to the C NMR,
1
1
which H nucleus is sterically nearer to the H nucleus
b
-
-
13
of H , we measured the NOESY (Fig. 5). The one di
-
1
-
mensional H NMR spectrum of POCD is shown on the
vertical axis and horizontal axes. The stronger the cross
peak of NOESY, the stronger the interaction of the dipole
two formal carbon signals were observed at 96.9 and 97.1
ppm, and their height ratio was 1:2. For assignment of
13
1
the 13C signals, the C H COSY (HETCOR) was mea
sured, and the result is shown in Fig. 2. From the result
-
-
-
tance was closer. With respect to the cross peak of the
between the protons, and the results showed that the dis
of the HETCOR, Ca was assigned to 96.9 ppm, and Cb
proton of Hb (4.90 ppm), a strong cross peak was ob
-
a
-
-
was assigned to 97.1 ppm. We ®rst expected that C shift
b
a
served between the multiplet (3.83±3.85 ppm) at the low
magnetic ®eld; only a weak cross peak was observed for
the multiplet (3.73±3.75 ppm) at the high magnetic ®eld.
From this observation, the signal of a proton at 3.83±
3.85 ppm was assigned to Hc, which is near to Hb, and
ed to a lower magnetic ®eld than C , because C is sur
rounded by two ±OCH2O units, while Cb is surrounded
on one side by ±OCH2O and on other side by ±OCH2CH2.
a
-
netic ®eld. From these observations, it was suggested
However, the result showed that C shifted to a high mag
the signal at 3.73±3.75 ppm was assigned to H d. Thus,
13
-
from the result of the chemical shift of the C NMR that
in the formal unit of three consecutive formals, the elec
1
-
each signal in the H NMR spectrum was con®rmed to
-
be in accordance with Ha, Hb, Hc, and Hd, which is shown
in the chemical structure of Fig. 1. In Table II, a precise
tron density on Cb may be higher than that on Ca.
1
-
Next, we compared the H NMR spectrum of TOCN
-
13
-
assignment of the C NMR spectrum of POCD is shown.
On the basis of the chemical shift of H NMR and
-
-
with that of 1,3 dioxolane and 1,3 trioxepane. For 1,3
dioxolane the chemical shift of the formal was 4.91 ppm,
1
13
-
-
C
NMR of POCD, Hc, which is surrounded with ±OCH2O
and ±OCH2CH2, shifted to a low magnetic ®eld, while
-
and for 1,3 trioxepane the chemical shift of the formal
was 4.92 ppm.14 Comparing the chemical shift of the for
-
mal of TOCN, Ha was 5.05 ppm, and Hb was 4.93 ppm.
Among the formal chemical shifts, Ha of TOCN is shifted
to the lowest magnetic ®eld, and this result was deduced
to be due to both sides being surrounded with a formal
unit. Among the formals connected to oxyethylene, the
b
-
H of TOCN, the formal of 1,3 trioxepane, and the formal
of 1,3 dioxolane shifted to the low magnetic ®eld in this
-
order; however, the difference was very small (0.01
ppm).
1
-
NMR Spectra of POCD and DEGF. The H NMR
spectrum of POCD is also shown in Table I. The area
strength of each spectrum is 1:2:2:2 in the order from the
low magnetic ®eld. As for the formals, a similar situation
was observed for POCD; Ha was assigned to 5.00 ppm
and Hb was assigned to 4.90 ppm from the order of the
low magnetic ®eld.
As for the oxyethylene, as shown in Fig. 3 each signal
-
nals with ®ve splits on the left side (3.83±3.85 ppm) and
was split, centered at 3.79 ppm, to two symmetrical sig
-
right side (3.73±3.75 ppm) because of spin±spin cou
pling.
To assign Hc and Hd, we measured the HETCOR. The
FIG. 2. HETCOR spectrum of TOCN.
APPLIED SPECTROSCOPY
1071

FIG. 4. HETCOR spectrum of POCD.
served in the compound with three consecutive formals
-
in one molecule, although this nonequivalence of the pro
ton of oxyethylene was not observed for the compound
with one formal in one molecule. For the compound with
-
one formal, the movement of the ring may not be re
stricted; thus mobility of each methylene proton in the
-
oxyethylene unit may be signi®cant. Thus, each methy
lene proton in the oxyethylene unit may be equivalently
observed, while for the compound with three formals, the
ring size is large; thus the movement of the ring may be
restricted. Thus, the chemical shift of each methylene
proton in the oxyethylene unit may be separated.
1
-
NMR Spectra of HOCP and TEGF. The H NMR
spectrum of HOCP is also shown in Table I. The area
strength of each spectrum is 1:2:2:2:2 in the order from
-
the low magnetic ®eld. As for the formals, a similar sit
uation was observed for HOCP; Ha and Hb were assigned
from the order of the low magnetic ®eld.
As for the oxyethylene, as shown in Fig. 3, each signal
1
c
H NMR spectra of H and Hd of POCD (A), and Hc, Hd, and
-
FIG. 3.
He of HOCP (B).
Hd, which is surrounded with ±CH 2OCH2 and
±OCH2CH2, shifted to a high magnetic ®eld. On the other
hand, Cc shifted to a magnetic ®eld higher than Cd; thus,
the electron density of Cd may be higher than that of Cc.
DEGF is the cyclic formal whose chemical structure
corresponds to POCD and has only one formal. In Table
1
-
I, the H NMR spectrum of DEGF is shown, and its as
signment is also shown. In the spectrum, two signals
-
-
-
were observed whose strengths were 1:4, and these sig
nals were assigned to the protons of the formal and ox
yethylene, respectively. The chemical shift of the formal,
Ha, was 4.90 ppm, the same value of the chemical shift
as Hb of POCD. It was remarkable that in POCD, Hc and
d
-
ical shifts, while in DEGF, the proton of oxyethylene is
H of the oxyethylene were observed at different chem
-
-
-
observed at the same value, and spin±spin coupling dis
appeared, thus showing one signal. That is to say, a non
equivalence of the proton of the oxyethylene was ob
FIG. 5. NOESY spectrum of POCD.
1072
Volume 54, Number 7, 2000

FIG. 7. HETCOR spectrum of HOCP.
FIG. 6. NOESY spectrum of HOCP.
was split, centering at 3.74 ppm, two symmetrical signals
with six splits to the left side (3.75±3.79 ppm) and right
side (3.68±3.73 ppm) because of spin±spin coupling, and
one single signal was observed at 3.66 ppm.
-
was in nonequivalence, and spin±spin coupling was ob
served, while the proton of the oxyethylene, which is
connected to one formal, is in the equivalent magnetic
c
d
e
-
-
lene, as with POCD, we measured the NOESY (Fig. 6)
®eld environment, and no spin±spin coupling was ob
served.
To precisely assign the H , H , and H of the oxyethy
1
and HETCOR (Fig. 7). As for the H signals, Ha, Hb, Hc,
Hd, and He were assigned from the order of the lower
magnetic ®eld, and the NOE cross peak between H b and
CONCLUSION
1
13
Hc was strong, while the cross peaks between H b and Hd,
-
-
Comparing the H NMR and C NMR spectra for the
three novel cyclic formalsÐ TOCN, POCD, and HOCPÐ
13
and between Hb and He, were weak. As for the C sig
-
nals, the signal at 91.3 ppm was assigned to C a, and the
one at 93.2 ppm was assigned to Cb. In the oxyethylene
signals, the signal at 66.5 ppm was assigned to C c, the
one at 70.7 ppm was assigned to Ce, and the one at 70.4
ppm was assigned to Cd.
-
-
which were obtained during the early stage of the copo
lymerization of trioxane and ethylene oxide, and assign
13
1
-
ing each signal on the basis of NOESY and C H COSY
(HETCOR), we obtained the following results:
-
-
1. The chemical structure of each compound was iden
ti®ed, and each signal of the NMR spectra was pre
cisely assigned.
-
As in the case of HOCP, the chemical shift of the car
bon atom was in the order of Cd, Ce, and Cc from the low
magnetic ®eld, and the electron density may be high in
13
2. The signal of the oxyethylene of POCD and HOCP,
-
-
C
this order. In Table II, the precise assignment of the
NMR spectrum of HOCP is shown.
TEGF is the cyclic formal whose chemical structure
which have three consecutive formal units, was in
dependently observed, and spin±spin coupling was
observed. The signal of the oxyethylene of DEGF and
TEGF, which correspond to the former compound, and
have only one consecutive formal unit, showed only
corresponds to HOCP, and has only one formal. In Table
1
-
-
I, the H NMR spectrum of TEGF is shown, and its as
signment is also shown. In the spectrum, three signals
were observed at a strength of 1:4:2.
-
one signal and showed no spin±spin coupling. Increas
ing the formal from one to three units, the oxyethylene
The chemical shift of formal Ha was 4.79 ppm. This
-
nomena were observed. There is some possibility that,
became nonequivalent, and spin±spin coupling phe
-
-
signal shifted 0.13 ppm to a higher magnetic ®eld com
b
pared to the H of HOCP. In the case of HOCP, the ox
yethylene signals, Hc, Hd, and He, were independently
-
yethylene signal (3.83 ppm) was observed at the single
-
with an increase in the formal unit, the chemical struc
ture of oxyethylene will be ®xed.
3. The chemical shift of the TOCN, POCD, and HOCP
b
observed, while in the case of the TEGF, H of the ox
13
b
-
-
C NMR spectra showed the possibility that the elec
-
signals, similar to the case of DEGF. However, H is rath
tron density of carbon (Cb) of the formal adjacent to
the oxyethylene unit is higher than that of the center
carbon (Ca) of the formal.
4. The chemical shift of the C NMR spectrum of the
er broad. Perhaps there is a small unresolved coupling,
suggesting that all four of the Hb protons are not quite
equivalent.
The spin±spin coupling, which was observed in the
case of POCD and HOCP, was not observed for DEGF
and TEGF, which both belonged to the same family.
13
-
-
-
compound having two and three consecutive oxyethy
lene units showed the possibility that the electron den
-
It is a remarkable fact that the proton in the oxyethy
lene, which is connected to three consecutive formals,
sity on the oxyethylene carbon is the highest for the
carbon (Cd ) next to the carbon adjacent to the formal.
APPLIED SPECTROSCOPY
1073

-
8. K. Weissermel, E. Fischer, K. Gutweiler, and H. D. Hermann, Kun
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Volume 54, Number 7, 2000