CONTINUOUS PROCESS FOR THE PRODUCTION OF CYCLOHEXYL MAGNESIUM HALIDES

PRODUCTION EN CONTINU DE CYCLOHEXYLHALOGENURES DE MAGNESIUM

English Abstract

ABSTRACT OF THE DISCLOSURE
A process and apparatus for the continuous production
of cyclohexyl magnesium halide. Cyclohexyl halide is fed at a
constant rate into a thermostatized column from the bottom thereof,
the column containing magnesium shavings fed from the top thereof,
and the desired cyclohexyl magnesium halide is recovered from the
top of the column. According to the invention, there is no
need to carry out the reaction in an inert gas atmosphere, such as
always required in known discontinuous processes. The invention
has the further advantage of enabling one to obtain a complete
reaction with a single passage of the halide into the column,
without having to resort to recycles, since the path followed
by the magnesium allows the same to reach the reaction area in
conditions of maximum reactivity. Cyclohexyl magnesium halides
are products particularly useful in the production of tricyclo-
hexyl tin derivatives which are valuable herbicides.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A continuous process for the production of
cyclohexyl magnesium halide, which comprises feeding cyclohexyl
halide at a constant rate into a thermostatized column from the
bottom thereof, said column containing magnesium shavings fed
from the top thereof, and recovering the desired cyclohexyl
magnesium halide from the top of the column.
2. Process as claimed in claim 1, wherein the
temperature of the column is kept at about 58-60°C and the cyclo-
hexyl halide is fed in a solution of tetrahydrofuran, the cyclo-
hexyl magnesium halide being thereby obtained in a tetra-
hydrofuran solution.
3. Process as claimed in claim 1, wherein, upon
starting, a solution of cyclohexyl magnesium halide in tetrahydro-
furan is introduced into the column, before feeding the
cyclohexyl halide.
4. An apparatus for the continuous production of
cyclohexyl magnesium halide, which comprises a thermostatized
column having a bottom part and a top part, the bottom part
containing a filling of Rasching rings and being connected
to means for feeding cyclohexyl halide, the top part being
provided with means for feeding magnesium shavings and with
means for discharging the desired cyclohexyl magnesium halide.

Description

1060901
The present invention relatcs to a process for the
production, in a continuous cycle, of cyclohexyl magnesium
halides.
As known, the cyclohexyl magnesium halides are products
which have recently acquired a lot of importance, for example
for the production of tricyclohexyl tin derlvatives, as the
tricyclohexyl tin halides and the tricyclohexyl tin hydroxides,
which are very useful as herbicides.
The cyclohexyl magnesium halides are at present
produced with a discontinuous process. Such a process has
its drawbacks, as there is always - while carrying out the
reaction at the basis thereof:
C6HllX~ Mg----~ C6HllMgX
wherein X is a halogen (especially C1) - the possibility of
explosions, in the event that an excessive amount of halide
should be fed when the reaction has not yet started. Moreover,
the reaction does not always develop in a complete way, and
it is anyhow necessary for it to be carried out in an inert
atmosphere.
All such drawbacks are eliminated by the continuous
proeess aceording to the present invention, which further
includes, compared to the known process, all the advantages of
eontinuous productions.
In aeeordanee with the invention, there is therefore
provided a continuous process for the production of cyclohexyl
magnesium halide, whieh comprises feeding cyclohexyl halide
at a constant rate into a thermostatized column from the bottom
thereof, the eolumn containing magnesium shavings fed from
the top thereof, and recovering the desired cyclohexyl magnesium
halide from the top of the column.
The present invention also provides an apparatus for
carrying out the above process, which comprises a thermostatized
~.
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~. 10~0901
column having a bottom part and a top part, the bottom part
containing a filling of Rasching rings and being connected
to means for feeding cyclohexyl halide, the top part being
provided with means for feeding magnesium shavings and with
means for discharging the desired cyclohexyl magnesium halide.
The in~ention will now be described in further detail
with reference to the accompanying drawing, which schematically
il]us-trates an apparatus in accordance with this invention.
With reference to the drawing, use is made of a column
10 1, having a diameter of 5 cm. and a volume of 2000 ml., containing
at the bottom 2 a filling of about 3 cm. of Rasching rings !
and being thermostated at 58-60C through circulation from the
hottom upwards of H2O into a jacket 3. Said column comprises at
the top a feeding mouth 4 and in its top part a spillway 5,
connected through a discharge 5' to a tank 6, while in the lower
part of the column, which also CompriSes a drain cock 7, there is
a feed pipe 8, into which the product contained in a tank 9 is
caused to flow through a constant delivery pump 10.
The column 1 is filled from the feeding mouth 4,
with shavings (about 420 gr.), Up to the height of the discharge
5'. About 200 ml. of 34-35% Grignard reagent solution in
tetrahydrofuran are then charged into the column; one waits for ~ -
the inner temperature to reach 58-60C and then one starts to feed
through the pipe 8 an anhydrous solution of cyclohexyl chloride
in tetrahydrofuran - in the proportions of 650 gr. of tetrahydro-
furan and 290 gr. of cyclohexyl chloride - in a quantity o 1 kg.
per hour. As one continues to feed said solùtion from the pipe 8,
the reaction product consisting of a 34-35% Grignard reagent
solution in tetrahydrofuran, starts to come out from the spillway
5. Said solution is collected into the appropriate tank 6.
The reaction yield, calculated on the cyclohexyl
chloride, is of 96-98~. The magnesium wastesaway mainly onto

10G09~
the bottom of the column 1, whercby the shavings of this
metal slowly drop down along the column itself; this latter
is kept constantly filled by frequently adding shavings
through the feeding mouth.
With this technique, there appears to be no formation
of residues, whereby there is no need for a periodic cleaning
of the column.
To interrupt the production, it is anyhow sufficient to
stop the feeding from the pipe 8, to cool down the apparatus
and to keep the column 1 filled in anhydrous conditions. To
start again the production, the inner temperature is brought
back to 58-60C and the cyclohexyl chloride solution is fed
again from the pipe 8.
Compared to the known discontinuous techniques, the
continuous process according to the invention, for the preparing
of cyclohexyl magnesium halides, has first of all the advantage
of being less dangerous, both because of the reduced quantities
of products in the cycle, and because of the elimination of the
risks connected with the starting of the reaction. In fact,
the reaction column can be kept full of Grignard reagent and of
Mg, in rest conditions at ambient temperature, even for prolonged
periods of time, and then it can be started again, in conditions
of normal efficiency, after having been brought back to the
reaction temperature. (On the other hànd, this make it
indispensable to use a solvent, which will keep the Grignard
reagent in solution, at ambient temperature, so as not to have
precipitations in the column).
~ further advantage of the process according to the
invention is that the path followed by the magnesium, according
to the type of feeding adopted, allows the same to reach the
reaction area in conditions of maximum reactivity. It is hence
possible to obtain a complete react1on with a single passage of
the halide into the column, without having to resort to recycles.

1060901
The fact should not be neglected, moreover, that the
tests carried out so far have not revealed the need to carry out
the reaction in an inert gas atmosphere, as was always required
in the known discontinuous processes; this is probably due to the
fact that, in the process using the apparatus according to the
invention, the reaction takes place in an area which is
definitely out of contact with air.
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