PREPARATION AND PROPERTIES OF n - A L K n ACRYLATES
July, 1944
bottom distillation flask that contained 1 mole (118 g.) of redistilled ethyl lactate and 3 moles (270 g.) of redistilled ethoxyethanol. The mixture was distilled with a high reflux ratio through a Vigreux column 60 cm. high to remove ethanol as it was formed. A small amount of freshly prepared catalya' LS added at about ,eight-hour intervals. After 45 ml. of ethanol had been removed during twenty hours, the vapor temperature rose to that of the excess ethoxyethanol,which was distilled. The desired ester was collected at 87-90" (5 mm.); ~ P1.4281. D The yield was 117 g. or 72% of the theoretical. Acetylation.-The lactic esters were acetylated with a 10% excess of acetic anhydride, using substantially previously described procedures.' The yields were 90 to 95%. Physical constants of the esters and details of the pyrolysis experiments are given in Tables I and 11, respectively. The fractions of the alkoxyethyl acrylates were small, and the physical constants observed for these samples are not considered to be as reliable as those (Table I) determined with larger samples prepared in connection with another investigati0n.O Soft polymers were obtained by heating
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(9) Rehbug and Fisher, "Preparation of Higher Acrylic Esters by t h e Alcoholysis of Methyl Acrylate," presented before the Division of Organic Chemistry a t the 108th meeting of the American Chemical Society, Pittsburgh, Pa., &pi., 1943.
[CONTRIBUTION FROM THE
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the acrylic ester fractions in the presence of benzoyl peroxide.
summary
The /3-methoxyethyl, B-ethoxyethyl, 8-butoxyethyl and tetrahydrofurfuryl esters of lactic acid were prepared by direct esterification and by alcoholysis of ethyl lactate. Acetylation with acetic anhydride yielded the corresponding a acetoxypropionates. Thermal decomposition of the P-alkoxyethyl aacetoxypropionates yielded the corresponding alkoxyethyl acrylates in yields of 26 to 47%o,along with acetic acid, acetaldehyde, carbon monoxide, carbon dioxide and hydrocarbon gases. A 70% yield of tetrahydrofurfuryl acrylate was obtained by the pyrolysis of tetrahydrofurfuryl acetoxypropionate. PHILADELPHIA, PA.
EASTERN .REGIONAL RESEARCH LABORATORY,
RECEIVED JANUARY
PHILADELPHIA,
17,1944
PENNSYLVANIAI1
Preparation and Properties of the %-AlkylAcrylates BY C. E. RIEHBERG Although acrylic acid is the simplest unsaturated carboxylic acid and its ester spolymerize readily, yielding useful resins, la no adequate study of the preparation and physical properties of the alkyl acrylates has been published. The commercially important methyl and ethyl esters are manufactured by treating ethylene cyanohydrin with the appropriate alcohol in the presence of sulfuric acid, a method which appears to be less suitable for production of higher alkyl acrylates.'" Although methyl acrylate can be made satisfactorily by pyrolysis of the acetyl derivative of methyl lactate, pyrolysis of higher n-alkyl aacetoxypropionates produces low yidds of nalkyl a~rylates.~J*4 Most of the published information on acrylic esters has appeared in the patent literature. The purpose of the present work was to prepare the n-alkyl acrylates by a generally applicable met$od6 and determine their common physical properbes. In addition, the esters were polymerized and examined briefly for a prelimi(1) This is one of fourRegional Research Laboratories operated by the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, United States Department of Agriculture. Article no' copyrighted. (la) H. T. N e h u , I n d . Eng. Chcm., 48, 267 (1936). (2) R. Burns, D. T. Jones and P. D . Ritchie, J . Chcm. Soc., 400, 714, 1054 (1935); U. S. Patent 2,265,814 (1941). (3) C. H. Fisher, C. E. Rehberg and Lee T . Smith, THISJOURNAL, 6S, 763 (1943). (4) Lee T. Smith, C. H. Fisher, W. P. Ratchford and M. L. Pein, I n d . Eng. Chcm., 84, 473 (1942). ( 5 ) C. E. Rehberg and C. H. Fisher, "Preparation of Higher Acrylic Esters by the Alcoholysis of Methyl Acrylate," presented before the Division of Orlcanic Chemistrv at the 106th meetinn of the American Chemical Society, Pittsburgh, Pa., Sept. 6 to 10, 1943.
AND C. H. FISHER
nary determination of the relation between the structure of the monomer and properties of the polymer. The higher acrylic esters were made in the present work by a l c o h o l y ~ i sa, ~method ~~ recommended by Neherla and used previously to prepare ethyl,b n-propylI6n-buty16and cetyl acrylates.8 Several of the n-alkyl methacrylates, including the n-propylIs n - b ~ t y l ,n-hexy17J0 ~ laurylll and stea.ryll1 esters, have been produced similarly by alcoholysis of methyl methacrylate. The ethyl, n-propyl, n-butyl, and dodecyl esters of acrylic a d d have been prepared also by direct esterification,I2 dehalogenation of alkyl cr,fl-dibromopropionates with zinc, 13,14.16 dehydrohalogenation of P-halopropionic e ~ t e r s , ' ~ , ' ~ acylation J' of the alcohol with acrylyl ChlorideI8J8dehydration of (6) C. T Kautter (to Rohm & Haas G. m. b. H 1, German Patent 706,792 (1941): (7) C. T. Kautter (to Rohm & Haas A.-G ), British Patent 520, 164 (1940). (8) Rohni & Haas A.-G., British Patent 491,880 (1938). (9) R. Hill, U. S. Patent 2,129,690 (1938); R. Hill and Imp. Chem. Ind., Ltd., British Patent 490,007 (1938). (10) T. White, J . C h m . Soc., 238 (1943). (11) H. J. Barrett and D. E. Strain. U. S. Patent 2,129,662 (1938). (12) (a) C. Moureu, M. Murat and L. Tampier, A n n chim., 16, 221-252 (1921); (b) Rohm & Haas A.-G., French Patent 818,740741 (1937). (13) F. Weger, A n n . , 441, 61-107 (1883). (14) W. Caspary and B. Tollens, rbrd., 161, 240-257 (1873). (15) P P. Kobeko, M. M. Koton and F. S. Florfnskii, J . AppIied Chcm. (U. S. S. R . ) , 19, 313-316 (1939): Chem. Abs., 88, 6795 (1939). (16) B. Jacohf and H. FikentsLher. U.S. Patent 1,934,613 (1933). (17) W. Bauer. U. S. Patent 1.864.884 (1932). (18) W. Rauer.and H. Lauth. U. S. Patent 1;051,782 (1934)
c. E. &"BERG
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Vol. 66
TABLE I PREPARATION AND PHYSICAL PROPERTIES OF THE n - A L K n ACRYLATES Alcohol Methyl converted acrylate Boiling accounted point Catalyst Yield, %" 'C. Mm. for, % b
i92;3-
Ester
Methyld Ethyld Ethyld Propyl* Butyl* Butyld Butyl Butyld Amyl Hexyl Hexyl Heptyl Octyl Xonyl Decyl Decyl Dodecvl' Tetradecyl' Hexadecy?
.. Toluenesulfoiiic acid HzSO4 GH~SOIH C7H?SOaH C~H~SOIH Al(OBu)i Al(t-BuO), HzSO.1 C~HISOIH H,SOI C~H~SOJH CrHWOzH C~HISO~H C7H7SOiH HzSOI GH7S03H C7H1S03H C7H7SOsH
62 99 100 96 93 85 66 87 99 99 80 92
7
4 2
...
62.7
104
99
82.6
86.6 79.5 84.4 80.6 59.3 87 90 95.7 80.7 w.3 91.5 83.8 81.9 92 90 53.3
80 760 43 103 43 103 44 40 35 8 39 10 39 10
90
... 94.2
. . ~
. . . . . .
76.5 99 92 88.4 88.7 89.6 100 88.7 61 3 87 96.3
48
.. ....
....
... ...
..
.... ... ... ,8903 40.33 40.76
1.4240 1.4285 .8882 44.95 45.30 1.4280 2 .... ... ... 89 24 7 57 1.0 1.4311 .%46 49.57 49.91 3 57 0.05 1.4360 .a1054.19 54.68 q1 5 76 0 . 2 1.4380 ,8785 58.81 59.26 06 7 120 5 1.4400 .8773 63.43 63.78 835 1.4400 ,8789 63.43 63.67 118 5 92 ,8727 72.66 73.15 120 0 . 8 1.4440 90 138 .4 1,4468 .87ooO 81.89 82.30 53.3 . . .8628 91.13 81.81 148 .04 1.4470 (30')' (30 1 Hexadecylh H&Oc 63 63 86.4 170 1 . 5 1. 4 6 0 .%13 91.13 91.79 (30')' (300) a Per cent. of theoretical on the basis o f alcohol consumed. Either a s recovered methyl acrylate or as the higher M.g. acrylic ester. c From the constants recommended by Eisenlohr. d Data reported in a previous paper (ref. 5). approximately 4". f M. p. approximately 14'. # A t 30" the density ( d 4 ) was 0.8622. h M. p. approximately 24 . Estimated value a t 20" is 0.8706. f Estimated value at 20' is 0.8691.
40
7 1.1
1.4040 0.9535 21.86 22.08 .4068 ,9234 26.47 26.68 1.4068 .9234 26.47 26.68 1.4130 ,9078 31.09 31.36 1.4190 ,8998 35.71 36.02
*
alkyl hydra cry late^,'^ or pyrolysis of alkyl CYacetoxypropionates.2 The alcoholysis procedure6 used in the present investigation consisted in rduxing methyl acrylate, which can be prepared satisfactorily from either ethylene cyanohydrin' or lactic acid,' with the higher alcohol in the presence of sulfuric or toluenesulfonic acid and distilling methanol azeotropically as it was formed. This was accomplished in most of the experiments by adding an excess of methyl acrylate and removing the methanol as the methanol-methyl acrylate azeotrope, which boils at 62-63'. Petroleum hydrocarbons distilling in the approximate range of .55 to 65" also can be used to distill the methanol azeotropically.6 1445
8 d
443
1425
.I
c
'3
1.405
0
24
4 8 12 16 Carbon atoms in the alkyl group. Fig 1 --Refractive indices and densities of the monomeric n-alkyl acrylate.. I'll
\\
t{
