Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
95~
2~,6~Q
PREPARATION OF ALKYLACRYLAMIDOGLYCOLATES
AND THEIR ALKYL ETHERS
This invention relates to a process for preparing
alkylacrylamidoglycolates and their alkyl ethers~ More
particularly, this invention relates to such a process
wherein an alkyl glyoxylate or its hemiacetal is reacted
with an acrylamid~ to provide an alkylacrylamidoglycolate
which may be subsequently etherified with a suitable alco-
hol.
Alkylacrylamidoglycolates and their alkyl ethers
can be readily polymerized and copolymerized with all common
ethylenically unsaturated comonomers such as styrene7 acry-
lates, methacrylates, acrylonitrile and the like. When
polymerized or copolymeriæed 9 alkylacrylamidoglycolates
and their alkyl ethers have been shown to provide reactive
sites in polymers employed as coating resins. These re-
active sites may provide crosslinking by self-condensation
at high temperatures or by use of added cross-linking agents
such as diamines.
Alkylacrylamidoglycolates and their alkyl ethers
are presently prepared by reacting an acrylamide with gly-
oxylic acid to provide an acrylamidoglycolic acid ln mono-
hydrate form. It is then necessary to isolate this inter-
mediate from the mother liquor and to remove excessive water
during the subsequent alkylation steps to obtain alkyl-
acrylamidoglycolate alkyl ethers. Water removal presents a
major difficulty in these current procedures. The use of
expensive water scavengers such as dimethoxypropane on a
molar basis is required to obtain acceptable Yields of the
alkyl ethers.
What is desired, therefore, is a process for preparing
alkylacrylamidoglycolates and their alkyl ethers which avoids the
necessity of isolating the acrylamidoglycolic acid and of remov-
ing excessive amounts of water during subsequent steps. The
provision for such a process would fulfill a long felt need and
constitu-te a significant advance in the art.
In accordance with the present invention, there is
provided a process for preparing an alkylacrylamidoglycolate which
comprises reacting an acrylamide with an alkyl glyoxylate or its
hemiacetal in essentially equal molar proportions at a temperature
in the range of about 50C to about 90C in the presence of a
polymeri~ation inhibitor.
In accordance with the presen-t invention, there is also
provided a modification of the process including the additional
steps of reacting the alkylamidoglycolate with a molar excess of
alcohol by distillation, said alcohol being selected from the
group consisting of aliphatic and cycloaliphatic alcohols of 1-6
carbon atoms and 1,2-dihydroxy alcohols of 2-6 carbon atoms.
The process of the present invention avoids the prepara~
tion of acrylamidoglyoxylic acid monohydrate, its isolation from
the aqueous mother liquor, and excessive water removal during
alkylation stepsO The process of the present invention allows
isolation of alkylacrylamidoglycolates which was not possible
employing the previously known process. The present process by
simplifying processing can resul-t in savings in costs and in
i~
2a
higher quality products.
In carrying out the process of the present invention,
an alkyl glyoxylate or an alkyl glycolate hemiacetal is reacted
with an acrylamide in essentially equal molar proportions to
provide an alkyl acrylamidoglycolate. Although variations in
the molar ratio of reactants is possible, no advantage appears to
result from such variations and purer products and be-tter ylelds
arise at essentially equal molar proportions.
. . . ~
~` ~L2~
The useful alkyl glyoxylate hemiacetals will have
the structure (I) and ~he alkyl glyoxylates will have ~he
structure (II):
0~ 0 0 0
11 11 11
H-C C--OR HC--COR
OH
(I) (II)
wherein each R is iDdividually, an allphatic or cyclo-
aliphatic radical containing 1 to 6 carbon atoms, or a
hydroxyaliphatic or hydroxylcycloaliphatic radical con-
taining 2-6 carbon atoms in which the hydroxyl group is on
the carbon atom adjacent that joined to the oxygen atom of
the alkyl glyoxyla~e hemiacetal. Typically, the R radicals
lS will be methyl, ethy~, propyl, isopropyl, bu~yl, isobutyl,
cyclohexyl, hydroxyethyl, and ~he like.
Alkyl glyoxylates or their hemiacetals may be
prepared by any convenient method. A preferred method to
form the hemiacetal is ~o react an essentially water-free
glyoxylic acid with a molar excess of alcohol while removing
water formed as a result of the reaction. The resulting
al~yl glyoxylate hemiacetal may be recovered from the re-
action mixture by vacuum stripping.
Acrylamides useful in the proceQs of the present
învention are readily available commercially and have ~he
structure:
R
~2C = C-- C
R' NH2
wherein R' is hydrogen or a methyl group.
In carrying out the process of the present inven-
tion, an alkyl glyoxylate hemiacetal or an alkyl glyoxylate
and an acrylamide in essentially equal molar amounts are
heated in the presence of a polymerization inhibitor to a
~2~
temperature in th~ range of about 50 to about 90C until
reaction is substantially complete, usually about l to 3
hours. Suitable polymerization inhibitors include for
example~ the methyl ether of hydroquinone, ethylenediamine
tetrace~ic acid, and ~he like, and the combinations thereof.
After the alkyl acrylamidoglycolate is ob~ained,
it may be isolated for use direc~ly in polymer or copolym~r
preparation or it may be employed without isolation in the
preparation of the alkyl ether thereof.
In preparing the alkyl ethers of the alkyl acryl-
amidoglycolates, an alcohol in excess of molar requirements
and an alkyl acrylamidoglycolate are heated in the presence
of an etherification catalyst ~o reflux temperature. Useful
etherification catalysts include sulfuric acid, paratolu-
enesulfonic acid, and the like. Water removal may be
accomplished by azeotropic distillation, if desired, or may
be accomplished by vacuum stripping also used to remove
excess alcohol. To help prevent premature polymerization
of the product, air sparging of the reaction mixture is
desirable. After the alcohol and alkyl acrylamidoglycolate
have reacted, the excess alcohol is removed by distillation.
This invention is more fully illustrated in the
examples which follow.
Exampl_ A
Prepara _ n of Ethyl Glyoxylate Hemiacetal
Glyoxylic acid monohydrate in the amount of 212
parts (2.25) moles, is charged to a suitable reaction
vessel. Hexane, in the amount of l,943 parts, and 2B
ethanol, in the amount of 419 parts ~approx;mately 9 moles)
are then addedO The mixture is heated to its boiling point
at atmospheric pressure. Water is removed continuously
using hexane to orm the azeotrope. The lower ethanol-rich
phase of the condensate (containing most of the water) is re-
moved. Additional 2B ethanol is added to the reactor to
compensate for the quantity removed to maintain the
e~hanol/glyoxylic acid molar ratio in the reactor at 4/l.
When no additional water can be removed (ap
proximately eight hours), the reaction mixture is cooled.
Upon cooling, the mixture splits înto two phases. The phases
are separated, the pale green lower phase contains pri-
marily the ethyl glyoxylate hemiacetal and ethanol. The
clear colorless upper phase is primarily hexane.
Examination of the products by 13C NMR shows about
two-thirds is the ethyl glyoxylate hemiacetal and about one-
third is the corresponding hemiacetal acid,
HO O
H-Ç 4
CH3CH2o OH
Small amounts of glyoxylic acid monohydrate and ethyl dihy-
droxyacetate are also found.
The ethyl glyoxylate hemiacetal is isolated from
the lower layer by vacuum distillation at 50 mm Hg pressure.
A total of 113 parts oE essentially pure product containing
about 1% water is collected, giving an overal] yield of 34%
based on the weight of the glyoxylic acid charge.
E_AMPLE B
Pre aration of MethYl~lYoxYlate Hemiacetal
P ,. ~ . _ _ _
A suitable reaction vessel is charged with 4,448
parts of 50% aqueous glyoxylic acid. Water is removed by
vacuum stripping at 100 mm Hg pressure. Water removal is
continued over a 9 hour time period with reactor temperature
ranging from 63C to 116C. Total water removal amounts to
2008 parts.
The stripp~d glyoxylic acid is cooled to about
85C and methanol (3 moles methanolll mole glyoxylic acid)
is added very gradually. The reaction is rapid and
exothermic and temperature can be maintained with a methanol
reflux while at least halE of the methanol is added. Near
the end of the methanol addition, heat is applied. Total
methanol addition is 2,890 parts during which the temper-
ature ranges from 78 to 92C. Reaction time is 2-1/2 hours.
The methyl glyoxylate hemiacetal is removed from
c
5i~31
the reaction mixture by vacuum stripping at 50 mm Hg pre-
ssure. The product, much of which is collected at about
75~80C, is about 80~/o pure, containing methyl dihydroxy
acetate (approximately 10%), water ~approximately 5%) and
5-10% of unidentified materials. A total of 2~466 parts are
collected; overall yield based on the initial weight of
glyoxylic acid is estimated at 50-60%.
EXAMPLE C
Preparation of Butyl Glyoxylate Hemiacetal
The procedure of Example I is followed with the
following excepti~ns. Glyoxylic acid, 50% aqueous, is char-
~ed in the amount of 1,000 parts Butanol is added in thP
amount of 2,000 parts. Water and butanol form an azeotrope
and water is removed by azeotropic distillation over 2.5
hours. The reaction m;xture is then distilled to give 1,337
parts (71% yield) of butylglyoxylate hemiacetal . The pot
rPsidue, 610 parts is butyl glyoxylate acetal (24%).
EXAMPLE I
reparation of Methyl Acr21amido&1ycolate
Methyl glyoxylate hemiacetal obtained from Ex-
ample B ;n the amount of 96.3 parts (0.8 mole) is ~harged
into a suitable reaction vessel and 1,000 parts per million
of methylether of hydroquinone and 50 parts per million of
ethylenediamine tetraacetic acid are added. A nitrogen
purge is then ~tarted. Acrylamide, in the amoun~ of 56.8
parts (0.8 mole), is charged and the reactor temperature
drops from 26C to 16C as some of the acrylamide dissolves.
The mixture is gradually heated and at 40-45C, all of ~he
acrylamide is in solution.
The temperature of the reaction mixture is grad
ually increased to 80-85C and held. Afte~ approxima~ely 1
hour in this temperature range, the reactor contents solid-
ify, yielding methyl acrylamidoglycolate.
~95~3
EXAMPLE II
Preparation of Ethyl Acrylamido~lycolate
Ethyl glyoxylate hemiacetal ob~ained from Example
A in the amount of 29.5 parts (0.2 mole) is employed along
with 14.3 parts (0.2 mole) of acrylamide following the
procedure of Example I, The reaction is run at 70-85C for
2.5 hours. Analysis of the product by 13C NMR shows a 90%
conversion with a 90% selectivity to ethyl acrylamido-
glycolate. Small amounts of ethyl acrylamidoglycolate
ethyl ether are also found.
EXAMPLE III
Pre~ ration of Butyl Acryl ~ ate
The procedure of Example I is again followed using
the following charge: butyl glyoxylate hemiacetal 315
parts (l.S moles), acrylamide 110 parts (1.5 moles), methyl
; 15 ether of hydroquinone 400 par~s per million and ethylene-
diamine tetraacetic acid 200 parts per million. The re-
action is run for 3 hours at 60-65C and then by-product
butanol is stripped under vacuum. The material is not
;solated, instead it is used directly to make butyl acryl-
amidoglycolate butyl ether.
EXAMP_E IV
Preparation of MethYl Acrylamido~lycolate Meth~l Ether
Methyl acrylamidoglycolate, as prepared in Exam-
ple I, in the amount of 100 parts (0.63 mole) is combined
with 200 parts of methanol (6.3 Loles), 0.10 parts of the
methyl ether of hydroquinone and 0.005 part of ethylene-
diamine tetraacetic acid and 5.0 parts of a 40% aqueous
solution of paratoluenesulfonic acid is added as catalyst.
The reaction mixture is heated for 4 hours at reflux temper-
ature and then cooled and filtered. Vacuum stripping of the
methanol results in crystallization of the product. An 85%
yield of methyl acrylamidoglycolate methyl ether is obtain-
ed.
~7
EXAMPLE V
Pre aration of But~l AcrYlamido~lYcolate Bu~yl E~her
P . , - ,
The reaction product of Example III is employed.
Butanol in the amount of 570 parts (7.7 moles~ is added.
Sulfuric acid, 2 ml concentrated acid, i5 added as catalyst
and the water is removed by azeotropic distillation ae 80-
85C under 190 mm Hg pressure over a period of 2.5 hours~ An
air sparge is used to help prevent premature polymerization
of the product. Butanol is then distilled to yield butyl-
acrylamidoglycolate butyl ether in 96% yield.
EXA~PLE VI
Butyl glyoxylate, 130 parts, is blended with 64
parts acrylamide and 1000 parts per million of monomethyl
ether of hydroquinone in a suitable reaction vessel. Tbe
mixture is slowly heated to 84C. After 2 hours the mixture
is cooled yielding the desired butyl acrylamidoglYcolate,
which is recrystallized from a suitable solvent.
EXAMPLE VII
Preparation of Butyl Methacrylamido~lycolate
The procedure of example VI was again follow2d
using the following change: butyl glyoxylate butyl hemi-
acetal 273 parts; methacrylamide 110 parts; methyl ether of
hydroquinone 0.27 parts. The reaction was run at 70 to 75C
for 1.5 hours. The material was not isolated, instead it was
used directly to make butyl methylacrylamidoglycolate butyl
ether.
EXAMPLE VI I I
Preparation of Butyl Methacrylamido&lycolate Butyl Ether
The reaction product of Example VI was employed.
Butanol 130 p~rts, butyl acetate 130 parts, and concentrated
3~ sulfuric acid 3.0 parts were added and the water removed by
azeotropic distillation under reduced pressure. A~ air
sparge was used to help prevent premature polymerization.
Butanol and butyl acetate were then distilled to yield butyl
methacryl amidoglycolate butyl ether.
