Note: Descriptions are shown in the official language in which they were submitted.
~131~6
The present invention relates to an improved process
for producing substituted thiocarbamates in a continuous cycle.
It is known from the literature that it is possible
to synthesize thiocarbamates by reacting a secondary amine
with carbon monoxide and sulphur in a suitable solvent and
thereafter subjecting the product obtained to alkylation.
The reactions are as follows:
(1~ 2 ~ ~ + CO + 5~ 2
. ~ Rl (+) Rl ! Rl ~ ¦ (+)
(2) ~ N-~j-S J H2 + 113X~ N-C--S R¦ NH X (
R2 R R2 R2
wherein: Rl, R2may be the same or different, consisting of
alkyl, cycloaklyl or aralkyl radicals, or may
form together a bivalent polymethylene radical.
R3 = an alkyl, cycloalkyl or aralkyl radical.
X = a substitutable group consisting of halide,
sulphate or sulphonate.
In essence, it happens that in reaction (1) the sec-
ondary amine reacts with the carbon monoxide and sulphur to give
rise to a substituted ammonium salt of thiocarbamic acid, after -
which in reaction (2) this salt reacts with an alkylating agent,
forming the substituted thiocarbamate.
Deep study of the mechanism by which the aforesaid
known reactionsoccur and a long series of experiments have now
enabled the Applicants to develop an improved process and ap-
paratus for producing substituted thiocarbamates.
~ - 2 -
3i~
In effect, heretofore the first of the above-
mentioned reactions has always been conducted in the presence
of an excess of sulphur by mixing equal molar amounts of
secondary amine and sulphur in the presence of carbon monoxide.
Moreover, the two reactions have always been carried
out separately and each in a discontinuous manner.
The present invention therefore proposes an improved
process for producing substituted thiocarbamates wherein a
secondary amine and sulphur in stoichiometric proportions (1
mole of amine ~ 0.5 mole of sulphur) are continuously fed
together in a suitable solvent into a reaction column sub-
jected to pressure by carbon monoxide while maintaining con-
tinuous circulation of the reaction solution in the column,
and the effluent from the colums is continuously subjected to
alkylation to continously produce the desired thiocarbomates.
The invention also proposes an apparatus for carrying
out this improved method,which comprises a column provided
downstream with an alkyla~ion reaction vessel from which the
desired substituted thiocarbamates are withdrawn continuous
In addition to the reaction column - which is prefer-
ably a column filled with Raschig rings - and the alkylation
reaction vessel, the apparatus according to the invention also
comprises a circulating pump for the liquid reactants and
control means for the temperature.
The reacted solution is withdrawn from the alkylation
reaction vessel in an amount equal (by weight) to that of
the supplied reactants.
If it is desired to carry out the continuous process
according to the invention with amine and sulphur in stoichiome-
tric proportion to each other, it is essential that the sulphur
be completely dissolved in the reaction mass which is introduced
into the reaction column; in fact, proceeding differently and
~- _ 3 -
supplying a sl-urry must be excluded because of the technol-
ogical difficulties which would arise in this case in the feed
and in achieving the condition of stoichiometric proportions.
According to the invention, the dissolution of the
sulphur is effected either by the amine itself, for example
as in the event of hexamethyleneimine being employed, or by
means of the addition of a certain amount of solution already
reacted in the column, when the amine does not succeed in
dissolving sulphur in the amount specified by the stoichio-
metry of the reaction, for example as when di-N-propylamine
or ethylcyclohexylamine is used.
In the second case, use is made of the property of
the solution of the thiocarbamic acid salt, obtained by the
first reaction of the process, of dissolving the sulphur. In
this regard, it is provided that the product which is formed
be utilized for solubilizing the sulphur, that is one of the
substances to be reacted. This obviously considerably extends
the number and types of amines which can be used for conducting
the said process efficiently.
The carbon monoxide is restored within the column as
it is consumed. The amount of carbon monoxide in circulation
is very small because of the smallness of the free volume in
the reaction column. As a consequence, the process and appara-
tus according to the invention have not only the normal advant-
ages of a continuous process ~high potentiality, small use
of labour, etc.), but also an extreme degree of safety.
The invention will now be described in greater detail
with reference to the accompanying drawing, which illustrates
diagrammatically an embodiment of the apparatus according to
the invention, and with the aid of the examples that follow.
The apparatus shown in the drawing provides two
mixing reservoirs SAl and SA2 which are connected alternately
. ~
by means of a pump Pl to a conduit CO leading to the top
of a reaction column C filled with Raschig rings RA. A reserv-
oir Bl containing carbon monoxide under pressure is also con-
nected to this column,
The reaction colum C has at the bottom a collecting
tank SC from the bottom of which there emerges a delivery con-
duit CE which bifurcates, being connected on one side to,
I ~
the conduit C0 upstream of a circulating pump P2 and on the
other side to a heat exchanger F1. The top of the column C
has a gas conduit CG leading to ve~ing means SR2, SR3. The
conduit C0 is equipped in large part with a heating jacket R.
The exchanger F1 (the purpose of which is to cool the
solution issuing from the collecting tank SC in order to
¦avoid decomposition of the product during transition to
¦ambient pressure) is connected to an alkylation reaction
¦vessel SA3 equipped with a stirrer and an overflow TP from
¦which a pipe TS leads to a storage tank SR1.
Example 1
S-ethyl-N,N-hexamethylene thiocarbamate is prepared by
the following reactions: 5-) (+)
CH2-CH2-CH2 !CH2-CH2-CH2 ~ ~CH2 CH2 -CH2--
(1) 2 ¦ NH+CO+S -~ ¦ N-C-S~ H2N l
CH2-CH2-CH2 , CH2-CH2 CH2 / H2-CH2 -CH
¦ /CH2-CH2-CH2 \ (-) CH2-CH2-CH2 ~+)
1(2~ -C-S~ H2 N/ l + ~C2H5)2 S04 -;
¦ ~CH2-CH2-CH2 0 CH2-CH2-CH2
¦ CH2-CH2-CH2 CH2-CH2-CH2 (~ )
N-C-S-C2H5 + ~ ~H2 S04C2H5
CH2-CH2-cH2 0 CH2 CH2 H2
¦ The reactants are introduced into a mixing reservoir, SA
or SA2 alternately, with a capacity of 10 litres, in the
¦following proportions:
¦ Hexamethyleneimine 99% 1000g (10 moles)
¦ Sulphur 160g ( 5 moles)
¦Vigorous stirring is carried out until complete solubilizatio
I -6-
1,....
of the sulphur is obtained and then there is introduced:
Anhydrous toluene 2600g
Stirring is maintained throughout the time of the feed.
Into the reaction column C, having a diameter of 5 cm
and a height of 400 cm and being filled with Raschi~ rings
and maintained at a temperature of 95~- 105C by heating with
a jacket and under a carbon monoxide pressure of 8-10 atm.,
there is delivered by means of the pump P1 the amount of
mixture required to fill the collecting tank SC up to the
level LI. The pump P2 is turned on so as to create a circulat on
in the column: the delivery of the pump is adjusted at a valu
between 60 and 200 l/h.
The mixture is left to circulate at a temperature of
95-105C for 30-60 minutes and then the feed of the column by
means of the pump P1 is resumed at a rate of 15-20 kg of
mixture per hour.
At the same time, there is tapped off from the collectin
tank SC an amount of reacted product equal to the fed amount
maintaining the level LI constant.
The carbon mon`oxide is supplied at the top and bottom
of the column and is consumed in a practically theoretical
amount; however, to avoid a concentration of gaseous impuri-
ties in the column, a certain amount of gas (1 or 2 bubbles
er second) is elimlnated through the venting means SR2 and
R3. The temperature ln the column C is preferably maintained
t 95-105C, making Use of heatlng applied in a jacket R
o the circulatlon condult C0, ina~much a~ at lower tempera-
ures the reaction is slower, while at higher temperatures it
s possible to have decomposition of the product obtained.
The pressure in the column is preferably maintained at
8 - 10 atm., which is sufficient for good progress of the
eaction. The quantity of product tapped off is cooled to
I
30-40~C in the e~changer F1 (it is necessary not to ~o below
¦this temperature so as not to produce crystallization of the
¦salt) and is delivered to the 10-litre ethylation reaction
~essel SA3.
¦ Simultaneously, diethyl sulphate is fed into the reactio
~essel SA3 (3.1 4.1 kg/h )
¦ The temperature in the ethylation reaction vessel SA3 is
~aintained at 35-40C. Fitted in the reaction vessel is a
~ateral outlet (calculated so as to achieve a permanence time
~f about 30 minutes in the reaction vessel) from which the
~eacted mass issues by overflowing and is sent to the storage
tank SR1. By this process there is obtained a toluene solutio
~f
¦ S-ethyl-N,N-hexamethylene thiocarbamate at about 23%.
~he total yield is higher than 90% of the theoretical.
~xample 2
¦ S-ethyl dipropylthiocarbamate is prepared by the follow
~ng reactions:
¦ CH3-CH2-CH2 . ¦CH3-CH2-CH2 ~~) CH2-CH2-CH3 ~)
~ NH+CO+S-->I N-C-S) H2 N\
CH3-CH2-CH2 ~CH3-CH2-CH2 0/ CH2-CH2-CH3
'H3-CH2-CH2 (-)~CH2-CH2-CH3 ¦~)
N-C-S H2 N\ ~ 2 5)2 4 >
3 H2 CH2 0 CH2-CH2-CH3
I CH3 CH2 CH2\ CH3-CH2-CH~ (+) (-)
> N~C-S-C2H5 + ~ NH2 SO4 C2 H5
¦ 3 2 2 CH3-Ch2-CH2
¦ The same apparatus as is described in Example 1 is used.
- 8 -
The reactants are introduced into a mixing reservoir,
SA1 or SA2 alternately, with a capacity of 10 litres, in the
following proportions:
- solution of the dipropylammonium salt of dipropyl-
thiocarbamic acid at about 23~ (in toluene): 3000 ml
- di-N-propylamine at 98% 678 ml
- sulphur 84 g
Stirring is carried out until complete solubilization of the
sulphur is obtained (it should be noted that the sulphur cann~ t
dissolve in the di-N-propylamine alone, for which reason it
is necessary to recycle the thiocarbamic acid salt) and then
there is introduced
Toluene 1500 ml.
The amount of solution of the thiocarbamic acid salt
introduced is not critical and is adjusted so as to obtain
complete solubilization of the sulphur.
The operating conditions are as follows:
-~ Column temperature 80-85~C
Tapping-off temperature 35-40C
C0 pressure in column 8-10 a~m.
;~ Delivery of recycling pump (P2) 80-200 l/h.
Delivery of metering pump (P1) about 13 l/h.
The ethylatlon of the solution containing the salt obtai _
d ln the c~lumn C is carried out, as in Example 1, in the
eaction vessel or tan'~ SA3, supplying dlethyl sulphate at a
ate of about 860 ml/h. By thls process there is obtained a
oluene solution of
S-ethyl dipropylthiocarbamate at about 23%.
he total yield is higher than 85% of the theoretical. The
ield can be increased to values higher than 95~ if at the
~ottom of reaction column there is connected a second,
Il I
finishing, column similar to the first.
NOTE
Preparation of S-propyl dipropylthiocarbamate is possibl
by this second method by the following reaction:
~CH3-CH2-CH2 \(-) CH2-CH2-CH3 (+)
~ -C-S¦ H2 N\ + CH3-CH2-CH2 I --3
CH3-CH2-cH2 ~ CH2-CH2-CH3
CH3 2 2\ CH3-CH2-CH2
~~ N-C-S-CH2-CH2- CH3 + \ NH.H I
CH -CH -CH
3 2 2 0 CH3-CH2-CH2
The alkylating agent is different: propyl iodide is fed into
the alkylation re~ction vessel.
~` The yield is higher than 85~.
. Example 3
::
:~ S-ethyl cyclohexylethylthiocarbamate is prepared by the
following reactions:
(1) CH2-CH
2 CH2 '` HC - Nl H + C O + S --->
CH -CH2 CH -CH
'~`''', . ~.~` : ` ~ . :~
CH -CH O \~-) CH2-CH (+)
->¦ H~ HC-N-C-S ~ H2 N ~ CH CH2
CH2-CH2 CH2 CH3~ CH2-CH3 CH2 ,CH2
.
CH2-CH2 0 -) CH2-CH2 ( + ?
~2) CH2 / 7 H 7 - CH /CH2 ~
~ ,~ ' \CH2-CH~ CH2-CH CH2-CH3 CH2 CH2
_
:~ - 10 -
'~:
'
CH2-CH2 0
+ (c2H5)2 S04 t C~2 HC-N-C-S-C2H5 t-
2 2 CH -CH
2 2 \ ( )
+ C~ HC - NH2 S04 C2 H5
CH -CH CH -CH
The same apparatus as is described in Example 1 is used.
The reactants are introduced into a mixing reservoir,
SA1 or SA2 alternately, with a capacity of 10 litres, in the
following proportions:
Solution of the ethylcylohexylammonium salt of
ethylcyclohexylthiocarbamic acid at about 23~ 2000 g
Ethylcyclohexylamine 97% 640 g
Sulphur 80 g
Vigorous stirring is carried out until complete solubilizatio
of the sulphur in the salt and the amine is obtained and then
there is added
Anhydrous toluene 1500 ml
The operating conditions are as follows:
Temperature oE cc)lul;,n (C) R0-100C
Tapping-off temperature 30-40C
C0 pressure in column 8-10 atm.
Dellvery of recycling pump (P2) 80-200 l/h.
Delivery of metering pump (P1)10-15 l/h.
The ethylation cf the salt obtained in the column is
carried out ln a continuous manner as ln Exampl~ 1 and 2,
supplying diethyl sulphate at a rate of 760-1140 ml/h. ~y
this process there is obtained a toluene solution of S-ethyl
cyclohexylethylthiocarbamate at about 23%.
The total yield is higher than 85%.
- 11 -
To increase the yield, it is necessary, as in Example 2,
to connect at the bottom of the column a second, finishing,
column similar to the first.
:~
~ - 12 -
