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I'EICIIICU aan. l, nH-l
2,414,056
UNITED STATES PATENT OFFICE
2,414,066
ISOMERIZATION
Win?eld Scott, deceased, late of Akron, Ohio, by
Ruth P. Scott, executrix, Akron, Ohio, assignor
to Wingfoot Corporation, Akron, Ohio, a corpo
ration of Delaware
No Drawing. Application August 9, 1943,
Serial No. 497,972
6 Claims. (Cl. 260-485)
1
2
This invention relates to the isomerization of
alpha-beta unsaturated acids and esters from the
cis to the trans form. The invention lies in the
C——— S
(5)
CHa-CH
use of a. conversion agent, without which no de
tectable conversion occurs. The invention in
%
é —-S~CH2OH
N
Mcthylol-Z-mercapto-li-methylthiazole
cludes the isomerization of such compounds in
which one or more of the hydrogens connected
(CH3)2N. C (S) S20 (S) .N ( CH3) 2
(6)
directly to a carbon atom have been replaced
Tetramethyl
thiuram disul?de
by chlorine, alkyl or other substituent. The ester
may be an alkyl ester, such as methyl, ethyl, 10 (7)
H
propyl, etc., or an aralkyl ester, such as benzyl,
etc. It includes the isomerization of angelic-acid
esters to tiglic-acid esters; cinnamic esters from
\/ S H
the cis to the trans isomer; chlormaleic-acid
esters to chlorfumaric-acid esters; citraconic 15
Piperidinium N,N-pentamethylene dithiocarbamic acid
acid esters to mesaconic esters; crotonic-acid
The invention will be illustrated by the follow
esters from the cis to the trans isomer; etc.
ing examples:
/\N_C_S>N
‘ I l / k/
According to this invention, the isomerization
Ezramplle 1
is effected in the presence of an isomerizing agent
which contains the grouping
A mixture of 15 grams of diethyl maleate and
0.3 gram of 2-mercapto-4-methylthiazole was
heated in an oil bath at about 140° C. Every five
minutes, a 0.4 ml. sample was withdrawn and
s
mixed with 0.6 ml. of Nujol. The consolute tem
in which the linkage between C and S or C and
perature of this mixture was determined, and
N may be a single or double bond. Representa 25 from it, the percentage of diethyl fumarate in
tive examples of such isomerizing agents, which
the reaction mixture was calculated. The results
include the thiazoles, thiazolines, thiuram disul
are given below:
?des, etc., are:
-—N—CI1—S’—
(1)
/
30
S
Time
Consolute
Per cent
° 0.
iumarate
temp.,
diethyl
C
\N/
Just after mixing ________________________ __
2-mercaptobenzothiazole
35
After heating to 140°
5 minutes at l40°__10 minutes at 140°“
15 minutes at 140°..
._
_
_
__._
20 minutes at 140° _______________________ __
(2)
25 minutes at 140°“
S
S
Benzothiazyl disul?de
(3)
_
NM. 25
__________ ..
95.25
80.50
69. 25
58. 25
12
30
44
57
48. 25
70
41. 50
78
30 minutes at 140°__
37. 00
83
35 minutes at 140° _______________________ _.
35. 25
85
Example 2
A mixture of 5 grams of monomethylmaleate
and 0.1 gram of Z-mercaptothiazoline was heated
at about 140° C. for one hour. The mixture dark
45 ened considerably during this time, but on cool
ing, monomethyl fumarate crystallized out.
Z-mercaptothiazoline
(4)
(l‘|J—-— S
CHa-C
4J~SH
%
N
2-mercapto-4-methylthiazole
Weight of product, 2.1 grams (42 per cent).
Example 3
Two and a half grams of 2-mercapto-4-methyl
50
thiazole were dissolved in 85 grams of water, and
100 grams of maleic anhydride were added. The
mixture was heated at its boiling point with stir
ring for about 2.5 hours. Upon cooling, the solu
55 tion yielded 90 grams of fumaric acid. Further
3
4
heating for 4 hours and distilling o? most of the
water resulted in the separation of an additional
22 grams of fumaric acid. Total yield, 95 per
cent.
The following table indicates the extent of
the conversion, using different isomerizing agents
at different temperatures, with the approximate
time required for the conversion, and in several
Example 4
Cl
instances the results are compared with those
obtained with known isomerizing agents:
A mixture of 15 grams of diethyl maleate and
Derivative converted
Agent
Th1???’ Helen?" 05%;???“
Maleic acid ____________ __
2. 25
109-101
89
2.0
4. 0
2. 5
109-101
109-101
109-101
77
88
76
Monomethyl maleate. _ - _
6. 5
1.0
109-101
140
42
Dimcthyl maleate . _
2. 5
190
80
160
75
D
Do _________________ __
_ _ __
0. 5
1% iodine ___________ --__..--_
1% Z-mercaptobenzothrazole_._
1% 2-mercapto-4-methylthiazole _________ __
95
1. 0
160
_
1. 0
160
60
.__
1.0
160
93
36
160
98
1% methylol-2-mercapto-4-methylthiazolc.__________________ __
1.0
1% cyclohexylamine derivative of zinc thiofuroate.
_
0.5
160
16
1% tetramethyl thiuram disul?de _________________ __
_
1.0
160
79
1% benzothiazyl disul?de ________ .1--. _______ ______.__
_
1.0
160
13
1% piperdinium pentamethylene dlthlocarbamlc acid__
1.0
160
41
1% Z-mcrcaptoquinoline ___________________________________ ..
1.0
160
(33
Other conversion agents include: Z-mercap
0.15 gram of 2-mercaptobenzothiazole was heated
at about 160° C. for one hour. A determination 25 tothiazole, thiazyl disul?de, 4-methylthiazyl
of the consolute temperature revealed that 60 per
disul?de, tetraethyl thiuram disul?de, tetra
=butyl thiuram disul?de, methYlol-Z-mercapto
cent of the maleic ester had been converted to
benzothiazole, methylol-2-mercaptothiazole, di
the fumarate ester.
Example 5
pentamethylene thiuram disul?de, diethyl am
30 monium diethyl dithiocarbamic acid, etc.
A mixture of 5 grams of diethyl maleate and
0.025 gram (0.5 per cent) 2-mercapto-4-methyl
thiazole was heated at about 120° C. for 80 min
What is claimed is:
1. The process of isomerizing diethyl maleate
to the diethyl fumarate which comprises the step
of heating the maleate in the presence of 2-mer
utes. Thirty-two per cent of the ester was con
verted to the fumarate.
35 capto-4-methyl thiazole at
Example 6
a temperature of
about 140° .C. until conversion is substantially
complete.
Two grams of Z-mercaptobenzothiazole were
2. The process of isomerizing dialkyl maleates
dissolved in 66.5 grams of water, and 118.5 grams
which comprises heating the dialkyl maleate in
of maleic acid were added. This mixture was 40 the presence of tetramethyl thiuram disul?de.
heated at its boiling point with stirring for about
3. The process of isomerizing dialkyl maleates
which comprises heating the dialkyl maleate in
maric acid which separated was ?ltered off, dried,
the presence of Z-mercapto-4-methyl thiazole.
and weighed. Yield, 91.5 grams ('77 per cent)
4. The process of isomerizing diethyl maleate
In determining the percentage of the trans 45 which comprises heating the compound in the
form of an alpha beta unsaturated acid or ester
presence of z-mercapto-ll-methyl thiazole.
prepared in accordance with the process of this
5. The process of isomerizing dialkyl maleate
invention, a mixture of Nujol (a special type of
which comprises heating the dialkyl maleate in
2 hours.
The solution was cooled, and the fu
mineral oil) and a sample of the reaction mix
ture resulting from the heating of the alpha beta 5
unsaturated acid or ester with any of the suit
able isomerizing agents of this invention, is heated
to about 120° C. (or some temperature higher
than the consolute temperature of the mixture)
and then the heated mixture is allowed to cool :
and the temperature at which the mixture just
begins to become clouded is observed and is re
ferred to as the consolute temperature. This
temperature is referred to a chart (on which is
plotted a series of consolute temperatures and 60
corresponding conversion percentages obtained
from known mixtures) and the corresponding
percentage conversion obtained.
the presence of a catalyst from the group con
sisting of 2-mercaptobenzothiazole, 2~mercapto~
thiazoline, 2-mercapt0-4-methyl thiazole, meth
ylol-Z-anercapto-ll-methyl-thiazole, tetramethyl
thiuram disul?de, Z-mercaptothiazole, thiazyl
disul?de, 4-methyl thiazyl disul?de, tetraethyl
thiuram disul?de, methylol-2-mercaptothiazole,
dipenta methylene thiuram disul?de and diethyl
ammonium diethyl dithio carbamic acid.
6. The process of isomerizing a dialkyl maleate
which comprises heating the dialkyl maleate in
the presence of 2i-mercaptobenzothiazole.
RUTH P. SCOTT,
Emecutrz'a: of the Last Will and Testament of
Win?eld Scott, Deceased.
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