Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~1~9S073
Mercaptocarboxylic acid esters are used in the practice
for numerous applications, for example as flotation or silver
protection agents, as corrosion inhibitors or, particularly, as
starting materials for plastics additives.
The present invention relates to mercaptocarboxylic
acid esters suitable especially for the latter application which
are not described as yet and which are distinguished by contain-
ing a hydroxyl group in ~-position of the alcoholic radical, and
furthermore to a process for the manufacture thereof.
The novel mercaptocarboxylic acid esters have the
formula OH R O
1 14 t
1 I C - O - C - R5 - SH
R2 R3
wherein Rl through R4, being identical or different, each are
a) hydrogen; the case where all four radicals are hydrogen,
however, being excluded; or
b) a phenyl radical or a cycloalkyl or cycloalkylene radical
having from 5 to 12 carbon atoms; or
c) a linear or branched alkyl radical having from 1 to 100
carbon atoms;
R2 and R3 optionally being common members of a saturated or un-
saturated alkylene chain having from 3 io 10 carbon atoms, and
the sum of all carbon atoms contained in the radicals Rl through
R4 being superior to 2 but inferior to 100, and R5 is an arylene
group or a saturated or unsaturated alkylene group having from
1 to 12 carbon atoms in the alkylene chain.
The novel mercaptocarboxylic acid esters are manufac-
tured by reaction of higher epoxides with mercaptocarboxylic
- 2 - q ~
'.,
~ .
lO9S~73
acids according to the following scheme:
/O~ OH R4 l
Rl ~ C - ~ - R4 + HOOC-R5-SH ~ Rl ~ C - C - O - C - R5 - SH
R2 R3 2 3
It was surprising and notto be expected that the re-
action proceeds is indicated, since, as is known, the reaction
of SH groups with epoxides readily yields ~-hydroxy-thioethers,
as described in J. Am. Chem. Soc. 82 (1960), p. 2511, where also
the reaction of mercaptoacetic acid and mercaptopropionic acid
with ethylene is discussed. According to this paper, products
having the following structure
IOH R4
1 ~ t ~ S - R5 - COOH
R2 R3
should be obtained. The analytic exarnination of the products of
the invention, however, clearly proves the reaction to proceed
according to the above scheme, that is, no ~-hydroxy-thioethers
are formed, but substantially mercaptocarboxylic acid esters are
obtained.
The symbols Rl through R4 in the above formula each
represent hydrogen (the case, however, where all four radicals
are hydrogen being excluded), or a phenyl radical, optionally
substituted by 1 or 2 alkyl radicals having from 1 to 9 carbon
atoms, chlorine or OH, or a saturated or unsaturated cycloalkyl
or cycloalkylene radical having from 5 to 12 carbon atoms and
being unsubstituted or substituted in the same manner as the
phenyl radical. Examples are phenyl, tolyl, xylyl, t-butylphenyl,
nonylphenyl~ chlorophenyl, hydroxyphenyl, cyclopentyl, cyclohexyl,
cycloheptyl, cyclooctyl or cyclododecyl radicals. The symbols
-- 3 --
~ :. ~: ,
~95~73
may furthermore represent a linear or branched alkyl radical
having from 1 to 100, preferably 6 to 60, carbon atoms, optionally
substituted by a phenyl group, a Cl to Cg a]kylphenyl group or
a cycloalkyl or cycloalkylene group having from 5 to 12 carbon
atoms. The radicals Rl through R4 may furthermore contain ether,
thioether, carboxyl, carboxylic acid ester, epoxide or mercapto-
carboxylic acid ester substituents of the formula
H H
-C-C-O-C-R5-SH, halogen substituents or C=C bonds.
OH O
Examples of these radicals Rl through R4 are:
2 18H37; CH2 S~C12H25; -cH2-o-c-cl7H
o
-(CH2)7-C-OH; -(CH2)7-fi-O-C H and -CH -CH=CH-C~O-CH
O O O
R2 and R3 may also be common members of a saturated or unsatura-
ted, optionally alkyl- or aryl substituted alkylene chain having
from 3 to 10 carbon atoms. In this case, the compounds of the
invention are esters the alcoholic moiety of which is for example
a B-hydroxycyclopentyl, ~-hydroxycyclohexyl or ~-hydroxycyclo-
octyl radical.
The radicals Rl through R4 may be identical or differ-
ent; howevex, as already mentioned, only three of them at most
can be hydrogen. A further limit is set by the fact that the sum
of all carbon atoms contained in the radicals Rl through R4 must
be superior to 2, but inferior to 100.
Preferred mercaptocarboxylic acid esters are those
where Rl is derived from linear, aliphatic hydrocarbons having
from 6 to 5%, preferably 8 to 40, and especially 12 to 36, carbon
-- 4 --
'
10950~73
atoms, and R2 through R4 each are hydrogen.
R5 represents an arylene group, for example a phen~1-
ene or naphthylene group, or a saturated or unsaturated alkylene
group having from 1 to 12, preferably 1 to 5, and especially 1
or 2, carbon atoms in the alkylene chain. The alkylene chain
may contain phenyl or alkyl substituents having from 1 to 16
carbon atoms; furthermore, the alkyl or phenyl substituents of
the alkylene chain may have carboxyl or carboxylic acid ester
groups derived from polybasic mercaptocarboxylic acids and the
partial esters thereof.
Suitable mercaptocarboxylic acids for the manufacture
of the mercaptocarboxylic esters of the invention are for example
mercaptoacetic acid, 2- and 3-mercaptopropionic acid, 2-, 3- and
4-mercaptobutyric acid, 2-mercaptovaleric acid, ~-mercaptohexanoic
acid, 3-mercapto-4-ethylenehexanoic acid, 4-mercaptocaproic acid,
3-mercapto-2,3-dimethylbutyric acid, 3-mercapto-4-hydroxybutyric
acid, 2-mercapto-3-methylbutyric acid, 3-mercapto-4,5-dimethyl-
hexanoic acid, 2-mercaptolauric acid, 2-mercapto-oleic acid, 2-
mercaptostearic acid, thiomalic acid and the semiesters thereof,
2- and 3-mercaptoglutaric acid and the semiesters thereof, thio-
citric acid and the partial esters thereof, dithiolactic acid,
2-mercaptopimelic acid and the s~miesters thereof,
2-mercaptosuberic acid and the semiesters thereof, thiosalicylic
acid and 3-mercapto-2 naphthoic acidi mercaptoacetic and 3-mercap-
topropionic acid being preferred.
Suitable epoxides are for example epoxidized olefinssuch as 2,3-epoxypentane, but especially epoxidized ~-olefins
such as 1,2-epoxyhexane, -octane, -dodecane, -octadecane; or long-
chain epoxides or epoxide mixtures, for example these of C20 to
24' 20 C28, C26 to C52, or C30+ ~-olefin fractions obtain-
-- 5
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able e.g. according to the Ziegler synthesis; furthermore arylsub-
stituted epoxides such as styrene oxide, tri~ and tetraphenyl-
ethylene oxide; glycidyl ethers of alcohols and phenols such as
octanol, octadecanol, phenol or nonylphenol; glycidylthioethers
of mercaptans such as octanethiol, dodecane-thiol, octadecane-
thiol or thiophenol; glycidyl esters of carboxylic acids such as
octanoic, lauric, stearic, benzoic, p-hydroxy-benzoic or p-t-
butylbenzoic acid; epoxidized fatty acids and fatty acid esters
such as 9,10-epoxystearic acid and the esters thereof; epoxidized
natural oils such as epoxidized caster oil or soybean oil, the
epoxide groups per molecule contained in these oils optionally
being reacted with mercaptocarboxylic acids either completely or
only partially; 9,10-epoxyoctadecanol, 2,3-epoxy-2,6-dimethyl-
octene-(7)-ol-(6); epoxy-2,6-dimethyloctadiene, 4,5-epoxyhexenic
acid-(2) methyl ester; cyclic epoxides such as epoxycyclopentane,
-hexane, -octane; epoxycyclooctatriene, 1,2- and 2,3-epoxytetra-
line, 3,4-epoxytricyclo-(0,3,4,1)-decene (obtainable from dicyclo-
pentadiene), or hexachloro-2,3-epoxynorbornene. Especially
suitable epoxide~ are cheap industrial-grade products such as
glycidyl ethers, -esters and -thioethers, especially epoxidized
fatty acids and fatty acid esters and epoxidized ~-olefins. Of
course, the starting epoxides and mercaptocarboxylic acids should
be chosen above all in view to the intended application of the
products of the invention.
The novel mercaptocarboxylic acid esters are prepared
as follows: The components are allowed to react, with agitation,
at temperatures of from 20 to 200, preferably from 50 to 150, and
especially from 80 to 120C. In order to obtain a quantitative
conversion, it is generally advantageous to use an excess of
-- 6 --
~Lq)95073
mercaptocarboxylic acid; however, an epoxide excess may also be
employed.
The reaction may be carried out in the presence or
absence of a solvent; suitable solvents are liquid, chlorinated
Iydrocarbons such as chloroform, carbon tetrachloride or chloro-
benzene, aromatic hydrocarbons such as toluene or xylene or ali-
phatic hydrocarbons such as hexane, heptane or gasoline fractions.
The reaction may also be carried out in the presence
of catalysts; suitable catalysts are iron-III chloride, alkali
metal salts of carboxylic acids such as sodium acetate, potassium
benzoate or potassium stearate, or ammonium salts of carboxylic
acids such as ammonium laurate, triethylammonium octoate or
tetraethylammonium stearate. Of course, also the corresponding
salts of the mercaptocarboxylic acids used may be employed. The
amounts of catalysts are from 0.1 to 5, preferably from 0.5 to 2,
parts by weight per lO0 parts by weight of mercaptocarboxylic
acid ester. The use of catalysts is recommended in the case of
epoxides having a poor reactivity; in general, however, the reac-
tion may be carr:ied out without a catalyst. The reaction time
is normally from l to 10 hours, and the proceeding reaction is
controlled by determining the epoxide number.
The mercaptocarboxylic acid esters of the invention are
interesting intermediate products for example for the synthesis
of plant protecting products and additives for lubricants or
plastic materials.
Some particularly typical representatives of the novel
mercaptocarboxylic acid esters are cited below; the invention,
however, is not limited to these substances:
'~
::
~095~73
OH O
2- hydroxydodecyl-mercapto- ( 1oH21 CH-CH2-O-C-CH2-SH
acetic acid ester OH l!
2-hydroxyoctadecyl-mercapto- ( 16 33 CH CH2-O-C-CH2-CH2 SH~
propionic acid ester OH
2-hYdroxy-c2o/24-al~yl-mer- (C18/22H /4s-CH-CH -O-C-CH -SH)
capto-acetic acid ester OH O
2-hydroxY-C24/28-alkyl-mer- ( 22/26H45/53 CH-cH2-o-c-cH2-cH2-sH)
captopropionic acid ester OH
2-hydroxy-c3o~ lkyl-mer- (~ C30H61-CH-cH2 C CH2
captoacetic acid ester H.2
2-hydroxycyclohexyl-mercapto- H2 ~ i~ OH
propionic acid ester ~ ~H
2 ~ 1~ 2 2
H2
bis-(2-hydroxy-C20_24-alkyl)-mercaptosuccinic acid ester
OH
11 11
H -CH-CH2-O-C-CH2-~CH-C O CH2 18/22 37/
SH
~-hydroxy esters obtainable by reaction of the epoxy groups con-
tained in epoxidized soybean oil with mercaptoacetic acid or mer-
captopropionic acid, the epoxide groups being reacted eithercompletely or partially, for example
S
OH O-C-CH2SH O~
CH3-(cH2)7-cH-cH-(cH2)7-c-o-cH2-icH-cH2-o-c-(cH2)7-CH-cH-(cH2)7-cH3
1O /O\
O=C-(CH2)7-CH-CH-(CH2)7-CH3
or isomers thereof.
The following examples illustrate the invention. In
order to characterize the products, the acid number AN (mg KOH/g,
-- 8 --
~09S0~3
according to DGF M IV 2 (57)), the saponification number SN (mg
KOH/g, according to DGF M IV 2 (57)), the flow point/drop point
(according to DGF M III 3 (57)) and the epoxide number EPN are
indicated (DGF = Deutsche Gesellschaft fur Fettforschung).
E X A M P L E 1:
After flushing with nitrogen, a four-necked flask hav-
ing a capacity of 1 liter and provided with agitator, inner
thermometer, condenser and dropping funnel is charged with 552 g
(3 mols) of 1,2-epoxydodecane. The contents of the flask are
heated to 110C in a slight nitrogen current. At this tempera-
ture, 322 g (3.5 mols) of mercaptoacetic acid are added dropwise
within 2 hours (exothermic reaction), and the reaction is then
allowed to proceed for a further 3 hours at 110C. Subsequently,
the contents of the flask are washed several times in a heatable
2 liter washing tube at 50C, until the washing water has
attained a pH of 6-7. The upper organic phase is then dried at
100C in a rotation evaporator under reduced pressure of 10 -
20 mm. A product being liquid at 30C is obtained.
Yield: 790 g 2-hydroxydodecyl-mercapto acetic acid ester =
96 % of the theoretical yield.
Analysis results: AN = 5,0; calc.: 0
SN = 195; calc.: 204,5
S = 11.2 %; calc.: 11.7
EPN = 0,03 %; calc.: 0 %
molecular weight: 310
IR spectrum: SH, ester, OH- and hydrocarbon
absorptions.
E X A M P L E 2:
131.5 g (1.43 mols) of mercaptoacetic acid are intro-
_ g _
.
. ' .
1095073
duced into the apparatus described in Example 1 and heated to
120C. At this temperature, 434 g (1.3 equivalents) of an
epoxide prepared from a C20/24-~-olefin mixture and having an EPN
of 12.9 % are added dropwise within 90 minutes (exothermic reac-
tion), and the reaction is allowed to proceed for a further 5
hours at 120C.
The contents of the flask are then diluted with 0.5 1
of toluene and washedto neutral at 65C in the washing tube
described in Example 1. According to the conditions indicated
in Example 1, the toluene is distilled off in a rotation evapora-
tor at a temperature of up to 100C and under reduced pressure
of up to 10 20 mm, thus leaving a slightly turbid melt.
Yield: 530 g 2-hydroxy-C20/24-alkylmercaptoacetic acid ester
(= 96 %) in the form of a wax-like white product having
a flow/drop point of 59/60C
Analysis results: EPN = 0.05 %; calc.: 0 %
AN = 6; calc.; 0
SN = 129; calc.: 132
S = 7.3 %; calc.: 7.5 %
MW : 473
IR spectrum: similar ~o that of Example 1
A sample of the ester was saponified for 3 hours with
2 n sodium hydroxide solution. After acidification, the water-
insoluble product obtained was analyzed, the results being as
follows:
AN = 9
SN = 9
S = 0.8 %, calc.: 0 %
This test shows that the reaction of the epoxide with mercapto-
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~L0~073
acetic acid yielded substantially the ester and not the thioester.
E X A M P E 3:
117.8 g (1.12 mols~ 3-mercaptopropionic acid and 470 g
(1.02 e~uivalents) of an 1.2-epoxy-C24/28-alkane having an EPN
of 9.55 % are heated to 120C in the apparatus described in
Example 1. After 5 hours at this temperature, the contents of
the flask are worked up as indicated in Example 2.
Yield: 555 g of 2-hydroxy-C24/28-alkyl-3-mercaptopropionic acid
ester (= 96 %) in the form of a wax-like, nearly white
product having a flow point/drop point of 79/79.5C.
Analysis results: AN = 9; calc.: 0
SN = 95; calc.: 99
S = 5.3 %; calc.: 5.6 %
EPN = 0.1 %; calc.: 0
~ : 569
IR spectrum: similar to that of Example 1
A product prepared in the same manner, but in the presence of
-- 11 --
"" ~L0~5~173
600 ml of xylene as solvent and worked up according to Example
1 had practically identical properties.
E X A M P L E 4:
78 g (0.85 mol) of mercaptoacetic acid are heated for
5 hours at 100c with 488 g (0.75 equivalents) of an 1,2-epoxy-
._C30-alkane having an EPN of 6.6% in the presence of 3 g of iron-
III chloride, and subsequently, the batch is worked up as indica-
ted in Example 2.
Yield: 545 g of 2-hydroxy-~C30-alkyl-mercaptoacetic acid ester
(= 96.5 %) in the form of a wax-li]ce, nearly white
product having a flow point/drop point of 87/88C.
Analysis results: AN = 3; calc.: 0
SN =72; calc.: 76
S = 4.2%;calc.: 4.3%
EPN= 0.3%;calc.: 0%
MW: 683
IR spectrum: similar to that of Example 1.
E X A M P L E 5:
147 g (1.6 mols) of mercaptoacetic acid are heated for
5 hours at 120C with 435 g (1.57 equivalentsj of the epoxidized
soybean oil cited having an EPN of 15.6% and a molecular weight
of 950, and worked up as usual.
Yield: 550 g of a yellowish, highly viscous liquid (=95%).
Analysis results: AN = 6; calc.: 0
SN = 269; calc.: 286
S = 7.9%; calc.: 8.7%
EPN= 0.1%; calc.: 0%
MW: 1370
In this Example, all epoxide radicals of the epoxidized
-' ~ - 12 -
~ :
~095073
soybean oil were converted to the B-hydroxy ester group.
E X A M P L E 6:
A four-necked flask having a capacity of 250 ml and
provided with the devices as cited in Example 1 is charged with
92 g (1 mol) of mercaptoacetic acid, and the contents of the
flask axe heated to 115C; at this temperature, 98 g (1 mol) of
cyclohexene oxide are added dropwise within one hour (exothermic
reaction). The contents of the flask are maintained at 115~C
for a further 5 hours, and subsequently washed with water and
worked up as indicated in the previous Examples.
Yield: 145 g of ~-hydroxycyclohexyl-mercaptoacetic acid ester
(= 76.3%) in the form of a colorless liquid.
Analysis results: AN = 9; calc.: 0
SN =280; calc.: 295
S = 16.4%; calc.: 16.8%
EPN=0.05%; calc.: 0
MW: 205
E X A M P L E 7:
This Example shows the further treatment of a mercapto-
carboxylic acid ester of the invéntion to give a plasticsadditive, and the stabilizing effect thereof in PVC.
1al95073
3.6 g (0.1 mol) of dioctyl-tin oxide and 124.5 g (0.2
equivalents) of 2-hydroxy-C24/28-alkyl-3-mercaptopropionic acid
ester of Example 3 are molten ln a 250 ml glass flask. Subse-
quently, a reduced pressure of 10 mm Hg is established and main-
tained at 100C for 3 hoursl the water of reaction formed beingtaken off via a cooling trap having a temperature of -80C. 158.0
g (99.5 %) of a light colored, wax-like organo-tin mercaptide of
the formula
(C24/28H49/s7-CH-cH2-O-c-cH2-cH2-s)2sn(c8Hl7)2
OH
having a flow point/drop point of 73/74C are obtained.
100 Parts by weight of a mass-polymerized polyvinyl
chloride having a K value of 67 were homogeneously mixed with 20
parts of dioetyl-phthalate, 0.5 parts of a lubricant on the
basis of montan wax (montanic acid ester of ethyleneglycol) and
1.0 parts of the ortano-tin compound.
For determining the dynamie thermostability, the mix-
ture was applied to a laboratory two-roll mill heated to 175C
and laminated at 20 rpm until the rough sheet had become black,
that is, for 80 minutes.
For a comparison, the same amount for the eommercial
dioctyl-tin-bis-thioglycolic acid iso-octyl ester stabilizer was
incorporated in a parallel test. Despite the tin content twice
as high the dynamic thermostability attained was also 80 minutes
only.
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i
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