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A cyclic trimer of 4-vinylpyridine
TetrahedronLettersNo.17, PP. 991)~lGGG, 1964. Pergamn Preaa Ltd. Printed in Great Britain.
A CYCLIC TRIMSR OF 4-VIWYLPYRIDIWE
by P. Longi, I.W. Dassi, F
Creoo, M. Cambini
From Istituto di Chimioa Industrialede1 Politoonioo,Milano, and Istituto Flioerohe, Wonteoatini S.p.A., Yilano (Received13 Lhrch 1964) Althoughthe oo-ordinatedpolymerizatioaof 2-vinylpyridine leads to the formation of crystallizablemacromolecules,the polymerizationof 4-vinylpyridinegives always non-orystallizablo linear high polymers (1): Supposing that this lack of crystallizationoould be attributed to some sterio hindranoeeand could be obviated, even though partially, by decreasing the molecularweight of the maoromoleoules,we investigatedon the thermal degradationof poly-4-vinylpyridiner. These reseamhes confirmed that no linear crystallizable' polymers of 4-vinylpyridine,even though having low molecular weight, oan be obtained, and demonstratedthat, among the degradationproduots of poly-4-vinylpyridineobtained by both ladioalio end anionio polymerization,a orystallineproduct was alwaye present, oorreeponding to a sym-tri(4-pyridyl)oyolohexane, thatis to say a oyolio head-totail trimer of 4-vinylpyridine(O). It was also found that partioularlyhighyMds
of oyolio
trimer oan be obtained when the degradation (at 23O-JOOcC)was oarrisd out by using, instead of the polymer, some of its salts (e.g. poly-4_ vinylpyridiniumhydrochloride).
(O) As far as we know, the formation of a oyolio trimer by degradation of linear macromoleculeshaving a hydrooarbonchain, has never teen described. 995
996
No.17
A cyclic trimer of kvinylpyridine
As a consequenceof the above-mentioned can be inferred that the most suitable procedure of the said trimer by a poly-4-vinylpyridine clude: a) the preparation preparation
researches,
degradation,
of poly-4-vinylpyridinium
run of 4-vinylpyridine
is hereinafter
polyme-
described.
(C H ) N&I (2.2 g) and anhydrous toluene (100 om3) are 252 3 under nitrogen atmosphere, in a 250 cm capacity three-
introduced,
necked flask, equipaed by mechanical thermostatic distilled
products.
of poly-4-vinylpyridine
As an example, a typical anionic co-ordinated rization
b) the
hydrochloride;
c) the isolation of the cyclic trimer from the degradation
a) Preparation
has to in-
of the oolymer of 4-vinylpyridine;
.%nd degradation
stirrer, dmpning
funnel, and
After stirring for 15 min., a recently
oil-bath at 50 V.
solution of 20 g anhydrous
4-vinylpyridine
is slowly added. After 5 hrs. at 60 “C, n-butanol
in 50 cm3 toluene
(5 om3) is added;
the flask content is poured in a 3 litres capacity separatory and water
funnel,
(1 litre) and oonc. HCl (30 cm3) are added; the toluene
layer is removed. Chloroform and of cont. NH aqueous
it
for the preparation
(800 cm3) and a solution of NH4Cl (30 g)
(150 cm3) in 400 om3 of water are added to the
3 layer. The lower phase, consisting of a chloroform solution
of poly-4-vinylpyridine, precipitated
is evaporated until
by pouring in n-heptane
15.5 g of polymer are weighed;
30-50 cm
and polymer is
(about 50 om3). After drying
intrinsic viscosity
mide at 30 'W : 0.2 * 100 cm3/g.
3
in dimethylforma-
No.17
A cyclic trimer of Lvinylpyridine
b) Preparation
and Degradation
997
of Poly-4-vinglpyridinium
Hydmw
chloride In a 500 orn3 capacity flask, poly-4-vinylpyridine is dissolved
in chloroform
3
(250 cm ) and gaseous hydrochloric
is let in at room temperature,
(15.5g) aoid
under stirring, until hydrochloric
acid is no longer absorbed. The whit8 precipitate
is dried at reduced pressure
(l-2
mmHg) at 50-60 OC. The poly-4-vinylpyridinium is heated, by a Wood alloy bath, af pressure
(14 rmnHg). Hydrochloric
hydrochloride
thus obtained
280 OC for 3 hrs. at a reduced
acid and 4-vinylpyridine
monomer
are evolved. o) Isolation of the orystalline
product
The final degradation
product is dissolved
3
(100 cm ) and treated twice in a separatory ammonia,
in chloroform
funnel,.Pirst
with aqueous
then with distilled water, until the Cl- ion abaenoe. The
chloroform
solution
is then dried (by removing the chloroform-water
azeotrope)
and slowly added to n-heptane
solid product, mostly consisting
product, mostly consisting
After filtering stallization
of the desired compound,
is further separa-
solution, by addition of n-heptane
(about 600 cn~~).
and drying it amounts to 9.5 g; purification
from methylethylketone
by cry-
is the carried out.
By using poly-4-vinylpyridine cal induced polymerization butyrronitrile
poly-
is separated. A light yellow crystalline
mers of 4-vinylpyridine,
ted from the remaining
(about 300 om3). A semi-
of linear low-molecular-weight
(23 g) obtained by radi-
( in benzene solution at 80 OC; azobisiso-
as initiator) and by following
in b) and o), 8.2 g of crude orystalline
the procedure described
product are obtained.
A cyclic
998 13) Properties
trimer of
and struoture
b-rlnylpyridine
of the Crystalline
No.17
Product
The pure product melts at 228.5 eC; it is soluble in chloroform,
methylene
and ketones! aliphatio
chloride, aromatic hydmoarbons,aloohols,
slightly soluble in ethyl ether, insoluble in cold
or oyoloaliphatio
hydrocarbons.
Analysis gives a nitro-
gen content of 13.03 $ (talc. for 4-vinylpyridine oryosoopy
in nitrobenzene
cular weight. Therefore vinylpyridine
- 13.32 I). By
solution , 312 is found as for the mole-
the substance
examined is a trimer of 4-
(calo. molecular weight:
315.4), to which either a
linear or a cyclic structure might be attributed. Trimer having linear structure groups, such as -CH3 or -CH=CH- or )C=CH2. spectrum
should have to contain On the contrary, I.R.
of the trimer (fig. 1) does not show any bands which
can be attributed
to the said groups ('O).
Fig. 1 - I.R. absorption spectrum of le, 3e, 5e-tri(4-Q-pyridylbyclo hexane in the molten state.
(00) The position of the absorption
bands of the above mentioned
10.34~ for trans -CH=CH- and 11.07~ for>G=CH2) 3' was determ:ined from the I.R. absorption snectra of 4-picoline, pyridine. trans -4-propenylpyridine and 4-isopropenyl/'he weak band at 7.26 p groups (7.28pfor
-CH
of fig. 1 must be attributed methyl group (2).
to the pyridine ring rather than to tile
A cyclic
No.17
trimer
We can therefore
of
kvinylpyridine
conclude for a cyclic structure
the trimer, that is to say (in the very likely hypothesis head-to tail enchainment
of the monomeric
of
of a
units) for the structure
of s-y-m-tri(4-p:;ridyl)cyolohexane. The exactness X-ray examination examination
of this hypothesis
of the nuclear magnetic
resonance
trimer in a CDC13 saturated solution
Fig. 2 - X-ray diffraction dyl)oyclohexane
spectrum
and by
spectrum of the
(4).
(CuKoC)
of le, je, 5e-tri(4-pyri-
in the solid state.
In particular, soectrum
has been proved by
of the trimer in the solid state (3)
interpretation
of the X-ray diffraction
(fig. 2) (““O) rciver,3 rhombohedrio
unit cell, wherein
oonstP,lts ref'e.,*;+? to n hexaPona1 system of axes, are: a = b = 17.50 _c 0.10 1; o = 4.6i 2 0.05 1 (most probable space
(on,)
Such a scectrum w'l-1~ m-de on a stretci:ed fibre obtained
mixture of cowercial
polystyrene
grout:
R3).
from a 1:l
and c:xlic trjmer OT 4-vinyluyridine.
1000
A cyclic trimer of kvinylpyridine
Since three molecules unit cell, it can be calculated,
No.17
of the trimer are present in the
as for its density, a 1.27 g/cm3
value quite near to the experimental
one of 1.28 g/cm3.
Taking into consideration possible packing of the molecules,
the unit cell symmetry and any
it can be concluded that a oy-
clic structure has to be attributed to the trimer, and the three pyridine ringe are arranged "ohair" ooxtiguration
in the equatorial belt, of the cyclohexane
(fig. 3).
Based on the structure factors obtained by the steric configuration
of fig. 3, a good agreement
culated and observed
intensities.
Fig. 3 - Sterio configuration (A = pwjection
is found between the cal-
of le, 3e, 5e-tri(4tyridyl)cyclohexane.
of the trimer molecule on (001) plane;
B = the same rotate. about a.....a through a 30° angle). References (1) 0. Natta, 0. Maszanti, P. Longi, G. Dall'Asta and F. Bernardini, J. Polymer Sci., 2, --
487 (1961).
(2) G. Zerbi, B. Crawford, J. Overend, J. Chem. Phys., _& (3) I.W. Baesi, in press. (4) A.
Segre,
this volume, P.
127 (1963).
A CYCLIC TRIMSR OF 4-VIWYLPYRIDIWE
by P. Longi, I.W. Dassi, F
Creoo, M. Cambini
From Istituto di Chimioa Industrialede1 Politoonioo,Milano, and Istituto Flioerohe, Wonteoatini S.p.A., Yilano (Received13 Lhrch 1964) Althoughthe oo-ordinatedpolymerizatioaof 2-vinylpyridine leads to the formation of crystallizablemacromolecules,the polymerizationof 4-vinylpyridinegives always non-orystallizablo linear high polymers (1): Supposing that this lack of crystallizationoould be attributed to some sterio hindranoeeand could be obviated, even though partially, by decreasing the molecularweight of the maoromoleoules,we investigatedon the thermal degradationof poly-4-vinylpyridiner. These reseamhes confirmed that no linear crystallizable' polymers of 4-vinylpyridine,even though having low molecular weight, oan be obtained, and demonstratedthat, among the degradationproduots of poly-4-vinylpyridineobtained by both ladioalio end anionio polymerization,a orystallineproduct was alwaye present, oorreeponding to a sym-tri(4-pyridyl)oyolohexane, thatis to say a oyolio head-totail trimer of 4-vinylpyridine(O). It was also found that partioularlyhighyMds
of oyolio
trimer oan be obtained when the degradation (at 23O-JOOcC)was oarrisd out by using, instead of the polymer, some of its salts (e.g. poly-4_ vinylpyridiniumhydrochloride).
(O) As far as we know, the formation of a oyolio trimer by degradation of linear macromoleculeshaving a hydrooarbonchain, has never teen described. 995
996
No.17
A cyclic trimer of kvinylpyridine
As a consequenceof the above-mentioned can be inferred that the most suitable procedure of the said trimer by a poly-4-vinylpyridine clude: a) the preparation preparation
researches,
degradation,
of poly-4-vinylpyridinium
run of 4-vinylpyridine
is hereinafter
polyme-
described.
(C H ) N&I (2.2 g) and anhydrous toluene (100 om3) are 252 3 under nitrogen atmosphere, in a 250 cm capacity three-
introduced,
necked flask, equipaed by mechanical thermostatic distilled
products.
of poly-4-vinylpyridine
As an example, a typical anionic co-ordinated rization
b) the
hydrochloride;
c) the isolation of the cyclic trimer from the degradation
a) Preparation
has to in-
of the oolymer of 4-vinylpyridine;
.%nd degradation
stirrer, dmpning
funnel, and
After stirring for 15 min., a recently
oil-bath at 50 V.
solution of 20 g anhydrous
4-vinylpyridine
is slowly added. After 5 hrs. at 60 “C, n-butanol
in 50 cm3 toluene
(5 om3) is added;
the flask content is poured in a 3 litres capacity separatory and water
funnel,
(1 litre) and oonc. HCl (30 cm3) are added; the toluene
layer is removed. Chloroform and of cont. NH aqueous
it
for the preparation
(800 cm3) and a solution of NH4Cl (30 g)
(150 cm3) in 400 om3 of water are added to the
3 layer. The lower phase, consisting of a chloroform solution
of poly-4-vinylpyridine, precipitated
is evaporated until
by pouring in n-heptane
15.5 g of polymer are weighed;
30-50 cm
and polymer is
(about 50 om3). After drying
intrinsic viscosity
mide at 30 'W : 0.2 * 100 cm3/g.
3
in dimethylforma-
No.17
A cyclic trimer of Lvinylpyridine
b) Preparation
and Degradation
997
of Poly-4-vinglpyridinium
Hydmw
chloride In a 500 orn3 capacity flask, poly-4-vinylpyridine is dissolved
in chloroform
3
(250 cm ) and gaseous hydrochloric
is let in at room temperature,
(15.5g) aoid
under stirring, until hydrochloric
acid is no longer absorbed. The whit8 precipitate
is dried at reduced pressure
(l-2
mmHg) at 50-60 OC. The poly-4-vinylpyridinium is heated, by a Wood alloy bath, af pressure
(14 rmnHg). Hydrochloric
hydrochloride
thus obtained
280 OC for 3 hrs. at a reduced
acid and 4-vinylpyridine
monomer
are evolved. o) Isolation of the orystalline
product
The final degradation
product is dissolved
3
(100 cm ) and treated twice in a separatory ammonia,
in chloroform
funnel,.Pirst
with aqueous
then with distilled water, until the Cl- ion abaenoe. The
chloroform
solution
is then dried (by removing the chloroform-water
azeotrope)
and slowly added to n-heptane
solid product, mostly consisting
product, mostly consisting
After filtering stallization
of the desired compound,
is further separa-
solution, by addition of n-heptane
(about 600 cn~~).
and drying it amounts to 9.5 g; purification
from methylethylketone
by cry-
is the carried out.
By using poly-4-vinylpyridine cal induced polymerization butyrronitrile
poly-
is separated. A light yellow crystalline
mers of 4-vinylpyridine,
ted from the remaining
(about 300 om3). A semi-
of linear low-molecular-weight
(23 g) obtained by radi-
( in benzene solution at 80 OC; azobisiso-
as initiator) and by following
in b) and o), 8.2 g of crude orystalline
the procedure described
product are obtained.
A cyclic
998 13) Properties
trimer of
and struoture
b-rlnylpyridine
of the Crystalline
No.17
Product
The pure product melts at 228.5 eC; it is soluble in chloroform,
methylene
and ketones! aliphatio
chloride, aromatic hydmoarbons,aloohols,
slightly soluble in ethyl ether, insoluble in cold
or oyoloaliphatio
hydrocarbons.
Analysis gives a nitro-
gen content of 13.03 $ (talc. for 4-vinylpyridine oryosoopy
in nitrobenzene
cular weight. Therefore vinylpyridine
- 13.32 I). By
solution , 312 is found as for the mole-
the substance
examined is a trimer of 4-
(calo. molecular weight:
315.4), to which either a
linear or a cyclic structure might be attributed. Trimer having linear structure groups, such as -CH3 or -CH=CH- or )C=CH2. spectrum
should have to contain On the contrary, I.R.
of the trimer (fig. 1) does not show any bands which
can be attributed
to the said groups ('O).
Fig. 1 - I.R. absorption spectrum of le, 3e, 5e-tri(4-Q-pyridylbyclo hexane in the molten state.
(00) The position of the absorption
bands of the above mentioned
10.34~ for trans -CH=CH- and 11.07~ for>G=CH2) 3' was determ:ined from the I.R. absorption snectra of 4-picoline, pyridine. trans -4-propenylpyridine and 4-isopropenyl/'he weak band at 7.26 p groups (7.28pfor
-CH
of fig. 1 must be attributed methyl group (2).
to the pyridine ring rather than to tile
A cyclic
No.17
trimer
We can therefore
of
kvinylpyridine
conclude for a cyclic structure
the trimer, that is to say (in the very likely hypothesis head-to tail enchainment
of the monomeric
of
of a
units) for the structure
of s-y-m-tri(4-p:;ridyl)cyolohexane. The exactness X-ray examination examination
of this hypothesis
of the nuclear magnetic
resonance
trimer in a CDC13 saturated solution
Fig. 2 - X-ray diffraction dyl)oyclohexane
spectrum
and by
spectrum of the
(4).
(CuKoC)
of le, je, 5e-tri(4-pyri-
in the solid state.
In particular, soectrum
has been proved by
of the trimer in the solid state (3)
interpretation
of the X-ray diffraction
(fig. 2) (““O) rciver,3 rhombohedrio
unit cell, wherein
oonstP,lts ref'e.,*;+? to n hexaPona1 system of axes, are: a = b = 17.50 _c 0.10 1; o = 4.6i 2 0.05 1 (most probable space
(on,)
Such a scectrum w'l-1~ m-de on a stretci:ed fibre obtained
mixture of cowercial
polystyrene
grout:
R3).
from a 1:l
and c:xlic trjmer OT 4-vinyluyridine.
1000
A cyclic trimer of kvinylpyridine
Since three molecules unit cell, it can be calculated,
No.17
of the trimer are present in the
as for its density, a 1.27 g/cm3
value quite near to the experimental
one of 1.28 g/cm3.
Taking into consideration possible packing of the molecules,
the unit cell symmetry and any
it can be concluded that a oy-
clic structure has to be attributed to the trimer, and the three pyridine ringe are arranged "ohair" ooxtiguration
in the equatorial belt, of the cyclohexane
(fig. 3).
Based on the structure factors obtained by the steric configuration
of fig. 3, a good agreement
culated and observed
intensities.
Fig. 3 - Sterio configuration (A = pwjection
is found between the cal-
of le, 3e, 5e-tri(4tyridyl)cyclohexane.
of the trimer molecule on (001) plane;
B = the same rotate. about a.....a through a 30° angle). References (1) 0. Natta, 0. Maszanti, P. Longi, G. Dall'Asta and F. Bernardini, J. Polymer Sci., 2, --
487 (1961).
(2) G. Zerbi, B. Crawford, J. Overend, J. Chem. Phys., _& (3) I.W. Baesi, in press. (4) A.
Segre,
this volume, P.
127 (1963).