Elastic N-Substituted Polyamides d
EMERSON L. WITTBECKER, RAY C. HOUTZ, AND W. W. WATBINS1 E. I . du Pont de Nemours & CompanyyInc., Busalo, N. Y . 1
weight appears to be more important in N-substituted polyamides where hydrogen bonding has been reduced than in unsubstituted polymers. Polymers were prepared for testing by solvent-casting transparent elastic films 3 to 7 mils thick and cutting into strips 0.25 X 16 em. or melt-spinning monofils. The samples were then colddrawn and tenacities and moduli expressed in grams per denier (g.p.d.) and elongations were measured on the Scott incline plane tester. The elastic recoveries were obtained by elongating the cold-drawn samples 100% for 60 seconds and allowing them to recover against no load for 45 seconds. The melting points of the polymers were obtained by hanging strips of films (0.25 inch wide, loaded a t 15 pounds per square inch) against a cylindrical chromium heater, equipped with a thermocouple on the surface, and recording the temperature a t which they broke. During the last 20" temperature rise, the heating rate was 5' to 10 O per minute. X-ray diagrams (except for 610) were obtained of film samples: (a) undrawn; (5) cold-drawn; and (c) cold-drawn, stretched and clsmped a t their maximum elongations. The x-ray diagrams were obtained with a General Electric XRD unit using a copper target tube run at 45 kv. and 15 ma. The Kor radiation was seIected by filtering through nickel foil. Plate distance was 5 cm.
Elastic N-substituted polyamides were obtained as a result of an investigation of N-substitution and a study of the effect of chemical structure on a number of physical properties, especially those important to a textile fiber. The size, nature, distribution, and amount of substituents can be controlled to produce polymers varying from the hard, tough, high-melting unsubstituted polyamides to soft, tacky, low-melting 100% N-substituted polyamides. Intermediate in properties are the fibers and films possessing long range elasticity.
T
HE use of a secondary diamine in the preparation of a linear polyamide (poly-N,N'-dimethylpentamethylene succinamide) was first disclosed by Carothers (6). Further study of N-methyl polyamides and analogous materials demonstrated the feasibility of introducing rubberiness into a polyamide. With this as a n objective, the present study of high-molecularweight N-alkyl polyamides, especially those with substituents larger than methyl, was undertaken., I n the meantime, Baker and Fuller (3)reported chain retraction and extension in a n x-ray study of N-methyl polydecamethylene sebacamides and suggested that it was the first stages of rubbery elasticity. The preparation of some N-alkyl polyamides by reacting a dibasic acid with a random mixture of diamines in which 5 to 90% of the amine groups are secondary ( 8 ) and the melting points of N-substituted polyamides (4)have been discussed. Additional uses for N alkyl polyamides include plasticization (5) and the improvement of polyamide dyeing ( 7 ) . If disecondary or secondary-primary diamines are used alone, or in conjunction with diprimary diamines in a polyamidation, all or any part of the amide linkages can be provided with alkyl radicals. This technique makes possible a n accurate control over: percentage of N-substitution; size and. nature of the substituent group; composition of the polymer chain; and at least a partial control over the distribution of the substituent groups along the polyamide chain.
CHEMICAL STRUCTURE AND PHYSICAL PROPERTIES
The primary effect of N-substitution is to reduce the polar coordination through the removal of amide hydrogen atoms ( S ) , thus permitting other forces to become important. Changing the chemical structure and intermolecular forces makes possible polymer properties ranging from those characteristic of an unsubstituted polyamide t o those of a low-melting, tacky polymer. The elastic polyamides are found between these two extremes. The properties of such a polymer, isobutyl 610 (40/20/40), are compared in Table I with rubber and 66 polyamide.
TABLE I. ELASTICPROPERTIES OF POLYMERS
EXPERIMENTAL
The N-substituted polyamides were prepared using reaction conditions such as described by Carothers (6). The following nomenclature has been devised t o facilitate discussion of this class of polyamides: the polyamide number abbreviation, such as 66 (polyhexamethyleneadipamide) or 610 (polyhexamethylenesebacamide), is preceded by the name of the substituent group and followed by a ratio of the mole percentages of the disecondary, secondary-primary, and diprimary diamines used. Thus, isobutyl 610 (+0/20/40) was obtained by condensing 40 mole % of N,N'-diisobutylhexamethylenediamine, 20 mole % of N-monoisobutylhexamethylenediamine, and 40 mole % of hexamethylenediamine with seba,cic acid. Fifty per cent of the amide linkages were thus substituted with isobutyl groups. To obtain optimum elastic properties in Nalkyl polyamides, it is desirable t o have a degree of polymerization of at l&st 50 and preferably 75 or higher. (A unit of polymer chain results from one diamine molecule and one dibasic acid molecule.) This requires pure intermediates and a careful balancing of polymer ingredients. A high molecular
Tenacity g.p.d." Elonpati& % 100% stretch-modulus, g.p.d. Elastio recovery, %
1 Present address, E. I. du Pont de Nemours & Company, Ino., Waynesboro, Va.
875
.
a
Isobutyl 610 (40/20/40) 1.Oto 1 . 7 250 to 400 0.3 to 0 . 5 95 to 99
Rubber 0 15 to 0 . 3 5 600 t o 1100 0.015 to 0.025 100
66
4.5 15 t o 25 25 t o 35
...
Grams per denler.
It is evident in this particular case that 50% N-isobutyl substitution has resulted in properties more like rubber than like 66 polyamide. The tenacity and the stretch-modulus of the elastic polyamide are higher than those for rubber, whereas the elongation is lower. The x-ray diffraction patterns (Figure 1) show that crystallinity and orientability are reduced markedly by N-substitution. SIZE AND NATUREOF SUBSTITUENT GROUPS. The desired substituent. group can be introduced into a polyamide by condensing the proper N-substituted diamine with a dibasic acid. Table I1 shows four 6O%-substituted 610 polyamides where only the substituent group has been changed-methyl, ethyl, isobutyl, and benzyl. (Other radicals investigated include n-propyl,
.
INDUSTRIAL AND ENGINEERING CHEMISTRY
876
Figure 1. S-Ray Patterns of Polyamides Samples shown i n each row, left t o right are undrawn, cold-draw,n, a n d cold-drawn, stretched a n d clamped at m a x i m u m elongation. (1st r o w ) 610; ( 2 n d row) isobutyl 610 (40/20/40).
TABLE 11. ALKPI. 610 (60'0'40) POLYXERS Tenacity, C. G.P.D. 147 1 43 142 1 40 146 1 00 140 0 75 a Obtained by extrapolation.
Allwl Radical Methyl Ethyl Isobutyl Benzyl
hJ.P.,
100% StretchAIodnlus, G.P.D. Ca 2 3" 0 40 0 30
0 26
Elongation,
Elavtic Recovery,
%
70
60 3 50 350 360
95 93 93
Vol. 40, No. 5
111, decreases as the size and branching of the alkyl group increases. Benzyl-substituted 610 polymers are not nearly as heat stable as other JY-alkyl 610 polymers, whereas rubberiness produced by cyclohexyl substitution tends to be sluggish. It should be emphasized that of all the possible variables a t hand in preparing N-substituted polyamides, changing t,he stze of the substituent group or even its character (from aliphatic to aromat>ic) produces t,he least effect on the elastic properties, with the exception of the methyl group. DISTRIBUTION OF SUBSTITUENT GROUPS. When both primary and secondary amines are involved in polyamidation, the distribution of the substituent groups (contribukd by the secondary amines) along t,he polymer chain might be influenced by a number of factors, including: ( a ) different rates of amidation; ( b ) different rates of hydrolysis and reforma.tion of amide linkages; ( e ) amide interchange; and ( d ) the relative amounts of disecondary, and dipriinary diamines in the " . secondary-primary, _ _ polymerization mixture. Onfy the last hf these can be regulated accurately, but this makes possible a partial control over distribution which markedly influences polgmcr structure and physical properties. The distribution of lateral substitucnts in a polymer prepared from an ,\7-alkyl-hesamethy1enediamine and a dibasic acid is necessarily regular. Depending on whether the diamines are incorporated into the chain head t,o tail or head i o head, every other amide linkage, or two out of every four amide linkages, is subst,itut,ed. Such a regularly substituted isobutyl 610 (O/lOO/O) polymer (from S-isobutylhexamet,hylenediamine and sebacic acid) was lower melting, more soluble in common solvents and had a lower elastic modulus and higher elongation than the less regularly substituted polymer.
isopropyl, n-butyl, lauryl, cyclohexyl, cyclohexylmethyl, and methoxyet,hyl.) Only polymers from combinations of disecondary and diprimary diamines are included in this t,able. When elongation and 1007, stretch-modulus are employed as criteria, N-mcthyl 610 polymers do not, exhibit,long range (rubberlike) elasticit,y in subst,itutions and distributions known to produce rubberiness in other S-substituted polyamides. This major difference is further illustrated in the x-ray diffraction patterns in Figure 2, which show methyl 610 (60/0/40)to be decidedly more cryst,alline and oriented in the cold-drawn condition than the corresponding ethyl- and isobutyl-substitut,ed polymers. Although ethyl 610 (60/0/40) and isobutyl 610 (60/0:'40) show increased orientation and crystallinity on being stretched i o their maximum elongations (Figure 2), these characteristics are retained only as long as the samples are clamped in the stret,ched condition. When relaxed, the x-ray patterns arc again those of the cold-dran-n samples (Figure 2). The methyl-substituted polymer, in contrast, retains its orientation and crystallinity on relaxing. Benzyl 610 (60/0/40) polymer gives patterns (Figure 2) similar to those of the corresponding isobutyl polymer. N o lecular chains constructed from Fisher-Hirschfelder models indicate that the difference in molecular size of methyl and ethyl radicals may account for a difference in lateral disorder of large magnitude. Lateral disorder is necessary for rubberiness (1) (cf. polyethylene and polyisobutylene). Changing the .substituent, group results in some variation of other physical properties. TT'ater absorption, as shown in Table
TABLE 111. Xi.rcui. 610 (0 / 1 O O i O ) POLYMERS Alkyl Radical R t...~ h v l. -
a
Propyl Isoprogyl n-Butyl Isobutyl Film immersed in water.
Water Abmrption,
7c"
1 0 .. 4. ~.
8.8 7,7 7.6 6.9
Figure 2.
X-Ray Patterns of Polyamides
Samples shown in each row, left and cold-drawn stretched and (1st row) methy; 610 (60/0/40); row) isobutyl 610 (60/0/40);
t o right, are undrawn, cold-drawn, clamped at m a x i m u m elongation.
(2nd r o w ) ethyl 610 (60/0/40): (3rd (4th. r o w ) benzyl 610 (60/0/40).
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1948
877
prepared from a 50 : 50 mixture of N,N’-diisobutylhexamethylenediamine and hexamethylenediamine with sebacic acid, isobutyl 610 (50/0/50) shown in Table IV. Both polymers have 50% of the amide linkages substituted. The former polymer was, in fact, similar t o a 1 0 0 ~ osubstituted isobutyl 610 polyamide which can have no ordinary chain interaction. Substituting every other amide linkage appears to prevent essentially all hydrogen bonding. Since melting point and increased solubility are excellent indicators of reduced polar coordination, it can be concluded that substituent groups larger than methyl create more lateral disorder in polar layers when they occur at regular intervals along the polymer chain than when they are irregularly substituted.
TABLE IV.
METHYL us. ISOBCTYL SCBSTITCTION M.P.,
c.
Methyl 610 (50/0/50) Isobutyl 610 (O/lOO/O) Isobutyl 610 ( 5 0 / 0 / 5 0 ) Isobutyl 610 (0/70/30) Isobutyl 610 (30/40/30) Isobutyl 1010 ( 5 0 / 0 / 5 0 ) a
155
75
150 120 130 152
100% StretchModulus, G.P.D. Ca. 2.4a < O . 0005 0 6 0.24
0.11 0.8
Elongation,
%
55 -3000 240 385
650 180
Figure 3.
Elastid Recovery
%
..
65 95 92 97 80
Obtained by linear extrapolation.
As a result of the effect of distribution, it should be possible to reduce the amount of regular substitution, from 50% t o 357” for example, and obtain a polymer possessing properties similar to those of one having 50% irregular substitution. Isobutyl 610 (0/70/30) was more rubbery than isobutyl 610 (50/0/50) shown in Table IV. Figure 3, second row, shows the x-ray patterns for this polymer. Further changes in distribution can be effected by changing the amount of secondary-primary diamine in a mixture of disecondary, secondary-primary, and dipiimary diamines. If this component is increased while the percentage substitution is held constant, the changes in properties are similar to those resulting from increasing the percentage substitution, provided the substituent is ethyl or larger. This is illustrated in Table IV by comparing isobutyl 610 (50/0/50) and isobutyl 610 (30/40/30) where the amount of X-isobutylhexamethylenediamine has been increased from 0 to 40% while the percentage substitution has been kept a t 50%. The rubberiness, as shown by elongation and modulus, has increased markedly. The distribution of the iateral substituents is as important as the degree of substitution in determining elastic polyamide properties. PERCENTAGE SUBSTITUTION. As the percentage of substitution is progressively increased, polar coordination is decreased and extensive changes in physical properties result. A wide range of properties is possible varying from unsubstituted 610 polymer u hich is hard, tough, and high-melting t o 100% substituted isobutyl 610 (lOO/O/O) which is soft, low-melting, tacky, and resinous. A series of polymers was synthesized from various ratios of N,N’-diisobutylhexamethylenediamine and hexamethylenediamine with sebacic acid; the percentage of substitution was the only variable. Figure 4 represents the change in meltiag point with N-substitution. The relationship is approximately linear, the melting point decreasing with increasing substitution. X-ray diffraction patterns also show that crystallinity and orientability diminished when chain interaction or hydrogen bonding was lessened by increasing N-substitution. Concurrently, the tenacity of fibers or films (when based on the original denier) decreased while the elongation increased from 15% to over 1 0 0 0 ~ (Figure o 5). The steep slope of the elongation curve in the range of 75% mbstitution indicates degradation of
X-Ray Patterns of Polyamides
Samples shown i n each row, left to right are undrawn, cold-drawn, a n d cold-drawn stretched a n d clamped at m a x i m u m elongation. ( Z s t row) isnbdtyl 69 (40/20/40); (2nd row) isobutyl 610 (0/70,’30).
polar forces to such a n extent that plastic flow becomes an important consideration. The 100Yo-substituted polymer can be stretched as much as thirty times its original length, but much of the elongation is nonrecoverable. From a practical standpoint this means that as polar coordination is lessened by N-substitution, the internal viscosity of the system becomes less and the elastic recovery and snap become better, up to about 75y0 N substitution. At this point the remaining hydrogen bonding, which is responsible for good elastic recovery, deteriorates and the elastic recovery gets progressively less until 100% N-substitution is reached. This is illustrated further in Figure 6, where the sum of cold-draw and elongation-to-break does not increase markedly until between 65 and 75y0 substitution. Individually, however, these two components change rapidly. Cold-draw in polyamides is dependent on intermolecular forces, and, as these forces are decreased by replacing amide hydrogens with alkyl groups, the amount of cold-draw diminishes and almost disappears at 75% substitution. At, the same time the amount of rubbery elongation is increased. Tenacity is ordinarily expressed as a function of the original denier and, as such, appears to decrease with increasing substitution (Figure 5 ) . Although the change in denier with elongation is ordinarily of little consequence, when dealing with fibers possessing long range elasticity, it becomes decidedly important. If such consideration is taken and the stress based on the denier a t the breaking point is plotted against N-substitution (Figure G), the tenacity of N substituted polyamides diminishes only very slowly as the polar forces are lessened. I n fact, 50 to 60% of the amide hydrogens
1
250
0
25
%‘ N
Figure 4.
so - SUBSTITUTION
75
100
Change in Melting Point with Percentage Substitution
-4
first row) show the azelaic acid polymer to be more disordered and therefore less crystalline and oriented than the corresponding sebacic acid polymer (Figure 1, second row). The properties of these two polymers are given in Table VI along with those of polymers from adipic, pimelic, ,and suberic acids. Although high molecular w i g h t s have been obtained from all of these, the acids containing eight or more carbon atoms are preferred because of greater meltstability of the resulting polymers a t higher temperatures. As the number of carbon atoms in the dibasic acid is progressively decreased from ten to six, the water absorptions of the resulting polymeis increase, whereas the melting points follow a zig-sag course similar to that for
Y
-3e -0 2%
% S Z ? -2;
2
0 0
- 1
$E I
1 - 0
m
I
-0
Figure 5 .
Effect of Percentage Substitution on Tenacity and Elongation
can be removed before the tenacity drops below 4 g.p.d. At 75y0 substitution, however, it begins to deteriorate rapidly. With increasing N-substitution, the 1 0 0 ~ ostretch-modulus decreases (Table V). As would be expected, decreasing chain interaction with N substitution increases solubility in common solvents, such as methanol-chloroform, until, a t 50 to 607, substitution, dopes can be prepared and clear elastic films cast. POLYMER CHAIXCOMPOSITIOX. It has been shown ( 2 ) that when one of the units of a linear condensation polymer is odd numbered, the chains pack with the polar layers perpendicular rather than inclined to the fiber axes. This arrangement permits less chain interaction. It follows that it should take less N substitution to produce rubberiness in such a polyamide containing a n odd numbered unit where the polar forces have already been reduced. This was demonstrated when an isobutyl-substituted 69 polyamide was found to have a lower melting point and a much higher degree of rubberiness than a comparable isobutyl-substituted 610 polymer. X-ray diagrams (Figure 3, B
TABLE
Lr.
ISOBUTYL
610
POLYMERSa
100% Stretchillodulus, G.P.D. 2.8 2.0 0.6 0.3 75 0 034 a On1 combinations of disecondary and diprimary diamines, as isobutyl 610 (25&0/75), etc. Percentage Substitution 25 40 50 60
'Oo0 800 0
t
COLD-DRAW PLUS ELONGATION TO BREAK Q
( % OF UNDRAWN LENGTH)
~
zoo.
0
25 %
-
50
75
100
N SUBSTITUTION
Figure 6. Relationship of Cold-draw, Elongation-toand stress at the ~ ~point to ~ the D~~~~~ ~ of Substitution
One 40/20/40 polymer listed in Table ?I was prepared using one third each of suberic, azelaic, and sebacic acids. The 50y0 3-substitution coupled with the longitudinal disorder introduced through the use of dibasic acids of various lengths (interpolymers) resulted in elastic properties similar to those of a corresponding polymer prepared from pimelic acid. The melting point was, in fact, lower.
TABLE T-I. ISOBUTYL 6 A a (40 '20 '40) Acid Sebacic (10) Azelaic (9) Suberic ( 8 ) Pimelic (7) Adipic ( G ) 8:9:10b a b
M.P., 0
c.
Mater Absorption, ,370
137
3.5
121
139 109
147 95
6.1 8.2 12.8 , .
looyo
Elongation,
%
350 900 250 700 326 750
Ptret.chModulus, G.P.D. 0.3 0.1 0.2 0.06 0.14 0.06
A = acid. One third (mole 70)each acid
The length of the diamine unit can also be altered, and the properties of such a polymer, isobutyl 1010 (50/0/50), are included. It appears to be somewhat less rubbery than the corresponding hexamethylenediamine polymer (Table IV) since the elongation is lower and the modulus higher. THEORY O F RUBBERY ELASTICITY I N POLYAMIDES. According to entropy considerations, fiber chains will exist in kinked, curled, random configurations unless this is prevented by other forces. When polyamides from primary diamines are cold-drawn, the polymer chains assume some molecular order and exist in an extended state. The strong polar forces of the amide linkages predominate and prevent the molecules from assuming random configurations which result in hard, high-melting, nonrubbery fibers with only 15 to 25y0 elongation. Reducing the polar coordination through S-substitution yields polymers which require new consideration. If X-isobutyl substitution is introduced into 610 polyamide, a long range elasticity rerults which is not produced by the same amount of S-methyl substitution. Since any substituent group, regardless of size, prevrnts hydrogen bonding through the actual removal of the amide hydrogen atoms, the larger groups must introduce lateral disorder which lessens hydrocarbon forces as well as polar forces. It seems reasonable to assume that in methyl-substituted polymers, with reduced polar forces, the tendency for the hydrocarbon sections of the polyamide chains to pack remains important enough that the molecules still cannot assume random configurations. I n polyamides substituted with groups larger than methyl, the balance of forces is such that large N-substituted sections of the molecular chains are coiled, twisted, or kinked randomly. The unsubstituted sections of the chain are presumably free to bond and form crystallites. In direct comparison elasticity in polyamides is a lwith rubber, ~ then, ithe long-range ~ ~ result of lateral disorder from A'-substitution, whereas in rubber
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1948
it is a result of lateral disorder created hy its cis-configuration. The hydrogen-bonded and crystallized portions of the N-alkyl polyamide chains act as cross linkages (covalent sulfur links in rubber) and contribute t o tenacity and elastic recovery. The mechanism of long range elasticity of N-alkyl polyamides is then the ability of those sections of chains with random configurations to straighten out on stretching and then coil, twist, or kinkagain on relaxing. The higher tenacity and modulus and somewhat slower elastic recovery of N-alkyl polyamides as compared with rubber are probably a result of the large number of hydrogen bonds which act as cross links, and result in a system with a comparatively high internal viscosity.
879
LITERATURE CITED
(1) Baker, W. O., BeZZLab. Record, 23, 97-100 (1945). (2) Baker, W. O., and Fuller, C. S., J. Am. Chem. Soc., 64, 23992407 (1942). (3) Ibjd., 65, 1120-30 (1043). (4) Blam B. S., Frosch, C. J.,and Erickson, R. H., IND.ENG.CHEM., 38,1016-19 (1946). (5) Brubaker, M. M., U. S. Patent 2,378,977 (June 26, 1945). (0) Carothers, W. H., Ibid., 2,130,523 (Sept. 20, 1938). (7) Faris, B. F., Ibid., 2,359,833 (Oct. 10, 1944). (8) Frosch, C. J., Ibid., 2,388,035 (Oct. 30,1945). RECEIVED May 24, 1947. Presented before the Division of Paint, Varnish, and Plastics Chemistry at the 109th Meeting of the AXERICAN CHEMICAL QOCIEFY, Atlantic City, N. J.
Substituted Vinylpyridines as Monomers for Synthetic Elastomers ROBERT L. FRANK, CLARK E. ADAMS, JAMES R. BLEGEN, AND PAUL
v.
SMITH
University of Illinois, Urbana, Ill.
A. E. JUVE, C. H. SCHROEDER, AND M. M. GOFF The B. F. Goodrich Company, Akron, Ohio
AMoh
Copolymers of dienes with substituted vinylpyridines TG the many comethod of Strong and Mchave some promise as synthetic elastomers. In the present Elvain (IS). monomers for butapapkr are described methods of preparation and the codiene and other dienes for the METHYL- 3 PYRIDYLCARpolymerization with butadiene and isoprene of a number BINOL. Two alternative methpreparation of synthetic of variously substituted vinylpyridines. Vulcanizates of ods were used for the preparubber the commercially the copolymers have a high moddlus and high tensile available 2-vinylpyridine has ration of this compound. strength as compared with GR-S and their flexingbeen described as capable The latter was preferred. hysteresis balance is for the most part superior to that of of copolymerizing to give 1. By the M s e r w e i n GR-S, although the hysteresis temperature rise is generrubbers superior in several Ponndorf Reduction. Forty ally higher. , respects to GR-S (1). grams (0.20 mole) of alumiIn the event that conum isopropoxide, 24.2 grams polymers of 2-vinylpyridins (0.20 mole) of 3-acetylpyshould find large industrial application, the potential supply from pidine, and 200 ml. of dry isoProPano1 were Placed in a coal tar picoline and formaldehyde would probably be inadequate. R ~ ~ ; x i ~ ~ $ ~ ~ d a $ The investigation reported herein was therefore undertaken to justed so that 8 drops per minute of distillate were collected. study the properties of various other vinyl-substituted pyridines The mixture was refluxed for 8 hours; a t the end of this time no test for acetone W a s obtained with 2,Pdinitrophenylhydrazine. wh:& might be used $0 supplement 2-vjnylpyridine. The cornThe remaining was then removed by pounds considered are 2-, 3-, and 4-vinylpyridines, 5-ethyl-2-vinylunder slightly reduced pressure. A mixture of 350 ml. of water pyridine, 2-methyl-5-vinylpyridine, 2-methyl-6-vinylpyridine, and 70 ml. of concentrated hydrochloric acid was then added t o 2,4-dimethyl-6-vinylpyridine, and 2-(2-pyridyl)-allyl alcohol. decompose the aluminum complexes. The solution was made Of these, 5-ethyl-2-vjnylpyrjdine and 2-methyl-5-vinylpyridine alkaline with sodium hydroxide, whereupon the precipitated are of particular interest as they are derived from aldehydealuminum hydroxide redissolved as sodium aluminate. The resulting solution was extracted with three 100-ml. portions of collidine (5-ethyl-2-methylpyridine) readily prepared in l ~ r from n ether and three 100-ml. portions of chloroform. The solvents paraldehyde and ammonia (4). were removed by distillation and the residue distilled under reduced pressure. The yield of product, boiling at 123' t o 125' C. (5 mm.) was 6.4 grams (26%), ny 1.5282. 2. By Catalytic Reduction. Two hundred forty-two grams (2.00 moles) of 3-acetylpyridine dissolved in 500 ml. of ethanol ' were hydrogenated in a steel reaction vessel for 50 minutes a t 150' C. with 24 grams of copper chromite catalyst. The initial 5-Ethyl-2-vinylpyridine 2-Methyl-5-vinylpyridine pressure (cold) was 1660 pounds per square inch. Distillation after removal of the catalyst by filtration gave 222.2 grams (90.3y0) of product boiling at 120' to 124' C. (4 t o 5 mm.), PREPARATION OF VINYLPYRIDINES n"," 1.5300.
-
~ ~ ~ ~ . ~ , ~ ~ - ~
2-VINYLPYRIDINE. Obtained from the Reilly T a r and Chemical Corporation, this monomer was redistilled before use, boiling (30 mm.); n'$' 1.5495. point 69' t o 71 ' 3-VINYLPYRIDINE. The general method of Iddles, Lang, and Gregg ( 7 ) was employed with some modification. The process was started with 3-acetylpyridine prepared according t o the
c.
3-VINYLPYRIDINE. A 19-mm. Pyrex tube was packed with aluminum oxide catalyst (Hydralo) and heated t o 325 ' c. Through the tube were passed 188 grams (1.52 moles) of methyl3-pyridylcarbinol at a rate of 16 t o 18 drops per minute. The temperature of the tube was maintained as closely as possible at 325' C. Chloroform was added t o the product and the water
