DE2432630A1 - Norbornene derivs. prodn. - by reacting dicyclopentadiene with unsatd. cpds. esp. acrylonitrile, in liq. phase - Google Patents

Abstract

Norbornene derivs. (I): where R1 and R3 = H or lower alkyl gp., which may be substd. by non-reactive substnts.; R2 = carboxy gp. or deriv. of this and R4 has the same meaning as R1, R2 or R3; are made by reacting dicyclopentadiene with a cpd. (II) or (III): in the liq. phase, by passing the reaction components (opt. premixed) directly into a reaction zone at 160-240 degrees C and pressures greater than autogenic pressure, and working up the resulting reaction mixt. Process is esp. useful for prodn. of exo-2-cyano-bicyclo 1,2,2 heptene-(5) (IV) from dicyclopentadiene and acrylonitrile with reduced by-prodt. formation and higher yields than known processes.

Description

"Process for the production of cyano-norbornene" The synthesis of endo- and exo-2-cyano-bicyclo-1,2,2-hepten- (5), called cyano-norbornene for short, by addition from acrylonitrile to cyclopentadiene was by K. Alder, K. Heimbach and R. Reubke, Chem. Ber. 91 (1958), page 1516 ff.

The reaction runs at 90-95 even at low temperatures (0 ° C-20 ° C) % Yield.

However, this type of synthesis is of little technical value, since only the dicyclopentadiene is stable on storage and is customary in the trade and accordingly cyclopentadiene can only be produced by the additional step of prior thermal cleavage of the dicyclopentadiene. silane has therefore tried to convert acrylonitrile directly with dicyclopentadiene in a one-step reaction: This reaction was also described by K. Alder et al in the above-mentioned reference (p. 1522, last paragraph): However, heating a solution of dicyclopentadiene and acrylonitrile in a molar ratio of 1: 2 in benzene to about 180 ° C. for six hours in an autoclave produced cyan -norbornene only in a yield of 63% of theory, but also 15% of an adduct of cyclopentadiene with cyannorbornene and other high-boiling products.

The formation of these byproducts is based on the fact that the cyclopentadiene, which is re-formed from dicyclopentadiene in the heat, continues to form polycycles in a subsequent reaction with cyano-norbornene. reacted: ÜLON 4ÜCN iÜtY½CN The object was therefore to produce cyanonorbornene from dicyclo pentadiene and acrylonitrile in an economical manner, ie primarily with better yields - that is, fewer by-products.

This object could be achieved by the present invention. The invention consists in a process for the production of cyan-norbornene by Implementation of dicyclo pentadiene with acrylonitrile in the liquid phase at increased Temperature and overpressure, which is characterized by the fact that the liquid Reaction components premixed or separated directly into one at the reaction temperature on about 160 to 2400C and a pressure above the autogenous pressure Introduces the reaction zone, and the fully reacted mixture in a manner known per se pulls off and works up.

Although Diels-Alder reactions are numerous and concur Surprisingly, it succeeded in getting through the literature the inventive procedure of the immediate introduction of the customary starting materials at about room temperature while skipping a heating phase into the reaction zone charged at the reaction temperature and pressure, in the implementation of dicyclopentadiene with acrylonitrile the one achieved so far, but Technically uninteresting yield of cyannorbornene is considerable, i.e. over about 90% d. Th. To increase.

Following the procedure of K. Alder et al. become the starting materials in a closed autoclave, starting from room temperature, only to about 18,000 heated and then left to react for a few hours. Obviously they are forming in the process larger amounts of by-products, which then leads to a reduction in the yield of cyano-norbornene has the consequence.

The process according to the invention can be semicontinuous or fully continuous ground executed. The use of an inert solvent such as benzoyl, Toluene or xylene is possible, but without particular advantage.

The design of the reaction zone has no particular influence on the reaction according to the invention. You can in a known manner, for example, autoclaves or Use flow tubes to which the reaction components are fed and from which one at another point, with flow tubes at the other end, which reacted completely Removes mixture or the reaction product. The starting compounds are preferably carried out from below and takes off the reaction product at the upper end of the reaction zones.

To start the reaction, it is advisable to completely open the reaction zone or partially with the end product cyan-norbornene or crude. Reaction product from to a previous approach to fill. The implementation in the not stirred Reactor can be in a simple tubular reactor (flow tube) or in a reactor take place with external or internal circulation. A loop reactor offers that Advantage that acrylonitrile and dicyclopentadiene always run in cyan-norbornene which leads to better heat dissipation and higher yields.

The starting components can be incorporated individually or premixed in flow tubes can be metered in at one end or distributed over the length of the pipe, of course can also be stirred as usual in the reaction zone.

The range from about 1600 to 240 ° C is selected as the reaction temperature, preferably about 1750 to 210 ° C. The residence time can range between approx. 0.3 and 8 hours lie. With reaction temperatures in the upper part of the specified range it is advantageous to have shorter residence times and at temperatures in the lower part to apply longer dwell times of the area accordingly.

The reaction is carried out at such a pressure that the liquid Phase is retained, so at pressures above about 2 atü to, for example, about 50 atm, with the range between about 5 and 10 atm especially for technical reasons It is advantageous that dicyclopentadiene and acrylonitrile in cyan-norbornene are retracted, the vapor pressure of acrylonitrile necessary for the pure compound already reached considerable values at the selected temperature, greatly reduced So it is sufficient z, B, at a reaction temperature of 185 ° C) the reactor under one Maintain pressure between 5 - 7 atmospheres The reaction components are generally in approximately stoichiometric amounts or a slight excess of acrylonitrile used; it is preferred to increase the yield and reduce the formation of more highly condensed adducts, an excess of approx. 2 - 10 mol% of acrylonitrile, which are essentially recovered in the work-up of the reaction products can.

It is also beneficial to add stabilizers for acrylonitrile such as hydroquinone, hydroquinone monomethyl ether, methylene blue, quinone, benzothiazine, Nitrobenzene, dinitrobenzene or dinitrochlorobenzene, with hydroquinone or hydroquinone monomethyl ether is preferred.

The amount of these stabilizers is generally about 0.01 to 2 percent by weight, preferably about 0.1 to 1 percent by weight, based on acrylonitrile.

Cyan-norbornene is a valuable intermediate for organic syntheses, especially for the production of diamines, which in turn are used for the synthesis of Polyamides are important.

The method according to the invention will now be based on the following examples will be explained in more detail, with a comparative example according to the prior art (after K. Alder et al) is prefixed.

Comparative example: A mixture of 1.0 kg (7.6 mol) of dicyclopentadiene, 0.82 kg (15.45 mol) of acrylonitrile, 4 g of hydroquinone monomethyl ether and 2 liters of benzene placed in a 5 l autoclave, in the course of approx.

Heated to 180 ° C. for 1 hour and held at this temperature for 6 hours. The distillation of the product gave: 1.123 kg of cyano-norbornene (62% of theory) 0.263 kg distillate with a boiling point of 150 ° C 0.37 kg tarry residue.

Example 1: An enamelled 10 l pressure vessel with a stirrer, heating and a metering pump connected to the bottom valve for the output components was provided, served as a reactor. To start the reaction, 9.0 kg of cyanonorbornene are used presented and heated to 1850C. Then the mixture prepared in a stirred tank became from 278 kg (2.1 kgRol) dicyclopentadiene, 223 kg (4.2 kgMol) acrylonitrile and 1.0 kg of hydroquinone monomethyl ether at a rate of 1.6 1 / hour. pumped in (mean residence time: 6.2 hours). The pressure holding valve was set to 6 atm. The product @@@ de withdrawn in the upper part of the boiler and through a pressure valve relaxed in a storage vessel.

491 kg of crude product were formed as a pale yellow, clear liquid.

Distillation of the crude product in vacuo gave: 452.2 kg (90.3% of theory) Th.) Cyan-norbonen Kp 2 1070C (endo: exo = 4: 6 10.6 kg acrylonitrile 24.4 kg high-boiling or non-volatile components.

Example 2: Under the same conditions as in Example (1) was a 4 mol% higher amount of acrylonitrile (232 kg) was used. The yield of cyano-norbornene increased to 463.9 kg (92.4 ß d.T., based on dicyclopentadiene).

Example 3: (Semi-continuous production) From 11.0 kg (8D, 3 mol) distilled dicyclopentadiene, 9.77 kg (184 moles) of acrylonitrile, and 35 g of hydroquinone a mixture was prepared, which reacted in 7 portions in a 5 l autoclave became. In this autoclave, the one with a stroke-thrust stirrer and a shortened Riser equipped; sar, 500 g of cyan-norbornene were presented. Then the The contents are heated to 1800C and the first portion of the mixture over the course of 2 hours pumped in. The temperature was between 1800 and 1850C. After pumping in is complete the temperature was held at 180 ° C. for a further 4 hours. Then the content Immediately relaxed via a cooled tube into a collecting vessel. To the approx. 500 g of raw product, din remained in the autoclave as a result of the shortened riser pipe immediately pumped the next portion of the mixture and as in the previous run treated.

From 7 successive batches of this kind, 20.92 kg of crude product were obtained obtain.

Distillation of the crude product gave: 892 g of low boiling components in a cold trap (-70 ° C) (mainly acrylonitrile) 176 g first run 19 228 g pure cyan-norbornene (of which 500 g were submitted for the first batch) 276 g of residue.

Yield 18.728 kg of cyano norbornene (94.5 ffi of theory, based on dicyclopentadiene) example 4: A standing, jacketed stainless steel tube with a diameter of 25 mm became the reactor Width and a length of 1 m.

There was a metering pump at the reactor inlet and a cooler at the reactor outlet attached with the following pressure maintenance valve.

At the beginning the reactor was filled with approx. 500 ml of cyan-norbornene and then with the help of a thermostatically controlled oil circulation to an internal temperature of 2000C brought. Then the pressure maintenance valve was set to 6.5 atmospheres and the metering pump 165 g per hour of a mixture of 1.393 kg of 95% dicyclopentadiene, 1.113 kg Acrylonitrile (= 5%% molar excess) and 10 g of hydroquinone monoethyl ether are pumped in.

This corresponds to a residence time of 3 hours. The system worked continuously and trouble-free over several weeks.

The crude reaction product collected after the pressure relief valve was pure distilled. The obtained-cyano-norbornene falls as a mixture of isomers endo and exo form and boil at 3? Torr at 1070C. The yield of distilled Product was 92% of theory. Th. Based on the pure dicyclopentadiene used.

Example 5: In the test facility according to Example (4) were at a Reaction temperature of 2100C and a pressure of 10 atü per hour 250 ml of the in Example (4) mentioned mixture - corresponding to a residence time of 2 hours - dosed.

The pure yield of cyano-norbornene was also 92.

Claims (3)

PATENT CLAIMS: 1. Process for the preparation of cyano-norbornene by reacting Dicyclopentadiene with acrylonitrile in the liquid phase at elevated temperature and Overpressure, characterized in that the liquid reaction components are premixed or separated immediately into one at the reaction temperature of about 160 to 240 ° C and a pressure above the autogenous pressure introduces reaction zone, and the fully reacted mixture is drawn off and worked up in a manner known per se. 2. The method according to claim 1, characterized in that the Acrylonitrile in an amount of about 2 to 10 mol% above the stoichiometrically necessary Amount sets in. 3. Process according to Claims 1 and 2, characterized in that the reaction in the presence of about 0.01 to 2 percent by weight, based on the Acrylonitrile, performed on acrylonitrile stabilizers.