JPS5953258B2 - Method for producing 4-nitro-N-methylphthalimide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 4-nitro N-methylphthalimide.

The use of methylene chloride as a solvent in the treatment of aromatic hydrocarbons with nitric acid in a sulfuric medium is important for a number of reasons.

Methylene chloride is completely stable in nitric acid at all concentrations up to its boiling point of 40°C or somewhat above and is resistant to degradation or conversion to other products. Only methylene chloride had this. This is compared with other halogenated derivatives such as chloroform and methylchloroform. Moreover, the other halogenated derivatives mentioned above, other than methylene chloride, do not have the desired volatility and solubility affinity for the reaction mixture and the subsequent nitrification products, ensuring efficient and rapid removal of the desired nitro compound. It became devoid of sexuality. It was also found that methylene chloride is the only material that can sufficiently maintain its integrity in a strongly acidic environment. In many cases, methylene chloride can be used to limit the temperature to around 42°C, thereby preventing localized high temperature areas and rapid temperature rises, thereby inhibiting the nitrification of aromatic compounds. There is an automatic restriction to dinitro derivatives, thus avoiding the formation of trinitro derivatives, which have explosive properties. Furthermore, methylene chloride obviates the need for excess nitric acid to be present and for some extra precautions to be taken to ensure that dangerous trinitro derivatives are not formed. . Methylene chloride is completely miscible with nitric acid at a concentration of 90% or more and accelerates the reaction when nitrification is slow.

However, methylene chloride is immiscible with nitric acid at concentrations below 80% and therefore reduces side reactions when highly reactive compounds are being nitrified. Since some of the nitrification products are solid, it has traditionally been difficult to avoid separation of nitrified compounds during the nitrification reaction. The use of methylene chloride avoided this difficult separation because it is a good solvent for nitrified compounds (as well as for unnitrified products). The aromatic compound nitrified by the method of the invention is N-methylphthalimide.

The amount of methylene chloride used as a solvent in the nitrification step is not critical.

However, = generally 1 to 5 parts by weight for each part by weight of aromatic compound.
It has been found to be advantageous to use 0 or more parts of methylene chloride. Since methylene chloride is also used as an extractant after the reaction is complete, the amount of methylene chloride initially used for solvent purposes can be minimized and the excess amount of methylene chloride can then be extracted. Add to the process. Generally, the minimum amount of methylene chloride used should be sufficient to keep the reaction temperature from rising above about 40-45°C at atmospheric pressure. Also, the amount of methylene chloride used must be sufficient to almost completely dissolve the aromatic compounds in the methylene chloride and to avoid undesirable separation of nitrification products until completion of nitrification is reached. When using methylene chloride for extraction purposes, K advantageously uses from about 0.5 to 8 or more parts of additional methylene chloride for the extraction function for each part of nitrification product, on a weight basis. It turns out that. In all cases where nitrification reactions are carried out, it is necessary to stir the reaction mixture to bring the reactants into closer contact, and a similar degree of agitation is also required when using methylene chloride for extraction purposes. .
The initial sulfuric acid solvent must be at least 90% concentrated sulfuric acid. If a lower concentration of H,SO, is used initially, the sulfuric acid will be undesirably diluted by the amount of water liberated by the nitrification reaction (with nitric acid);
As a result of this, the solubility of the nitrified products in the reaction mixture decreases, causing problems. butterfly ．． child. Q for X. When I finished the Q extraction process with Tanaka Mechirei, Washima was 0-1, but I was afraid of saying it 4)
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-An enemy?゜｜? :↑2;=:÷2: Must be relatively close to the stoichiometric amount required to do so.

However, as pointed out above, a virtually arbitrary excess of 0 nitric acid is not a critical problem since the CH2Cl2 solvent limits the degree of nitrification and avoids hazardous conditions and the possibility of decomposition of the explosive composition. No. One way to carry out the reaction is to perform the reaction with N-
Methylphthalimide is dissolved in methylene chloride, and this solution is placed in a reactor equipped with a stirrer and means for heating and cooling the reactor.

After heating the solution to the desired temperature (usually a reflux temperature of about 40-45°C), a mixture of concentrated nitric acid and concentrated sulfuric acid is advantageously allowed to sit for a period of time ranging from about 15 minutes to about 1 to 2 hours or more. Add. After stirring the mixture at reflux temperature for a period of about 30 minutes to about 2 to 3 hours, the mixture is cooled to room temperature. At this point, two distinct layers are usually visible. The upper methylene chloride layer is separated and the bottom acid layer is extracted with additional methylene chloride, preferably in several portions. The extract and the upper methylene chloride layer are passed through silica gel (or other suitable means) to remove residual acid and the methylene chloride is removed by evaporation to obtain the nitrified product. Continuous extraction of the bottom acid solution with methylene chloride was performed by Dean Stark.
It is advantageous to carry out the process in a closed-loop reactor, which resembles a rk) apparatus and is equipped with a stirrer in the extraction column into which the reaction products are introduced.

Methylene chloride (extractant) is continuously introduced into the bottom of the extraction column. At the top of the extraction column is an arm through which an overhead stream of extractant and reaction products (separated from H2SO4) is conveyed to a heater-equipped reservoir. This heater is operable in a range from about room temperature to 100° C., and its function is to evaporate methylene chloride and concentrate nitrified aromatic compounds. The methylene chloride vapor is condensed and continues to be recycled by gravity to the bottom of the extraction column. At this point, all nitrification products are in methylene chloride contained within the reservoir. As mentioned above, one advantage of using methipine chloride as a solvent during the nitrification reaction is that a lower degree of turbidity can be used and it is possible to use more than two nitro groups to prevent aromatic destruction, which can lead to hazardous conditions. The point is that there is actually no risk of excessive nitrification to the extent of forming nitrification compounds.

Generally, the temperature that is productive enough to carry out nitrification is about 40
-45°C. During the total nitrification reaction it is desirable to use an inert atmosphere, e.g. a nitrogen blanket.
stomach.

Generally, atmospheric pressure is sufficient to maintain the reaction, but it should be obvious to those skilled in the art that conditions below or even above atmospheric pressure can be used without departing from the scope of the present invention. It is. Vigorous stirring is provided throughout the reaction period. The following examples are provided to enable those skilled in the art to understand how to practice the invention, and are given by way of illustration only and not as a limitation in any way.

Unless otherwise stated, the extracted nitrified products were combined with methylene chloride and passed through a column of silica gel to remove traces of sulfuric acid.

Removal of methylene chloride was carried out under vacuum in a rotating thin film evaporator. Example 9 8.3% H2SO43OCC and methylene chloride 40cc
N-methylphthalimide 16.1f1 (0.
1 mono(he) was gently refluxed (approximately 41°C), where 98.1% HNO, 4.55CC (0.105 mol)
was slowly added to the reaction mixture over a period of 40 minutes.

Claims (1)

[Claims] 1. Forming a solution of N-methylphthalimide with methylene chloride and concentrated sulfuric acid of a concentration of at least 90%, and adding this phthalimide solution to the N-methylphthalimide at 1%.
4 was produced from the reaction mixture by treatment with concentrated nitric acid of at least 90% concentration in an amount close to the stoichiometric amount required to bond the nitro groups at a temperature of 40-45°C and then with methylene chloride. - A method for producing 4-nitro-N-methylphthalimide, which comprises extracting nitro-N-methylphthalimide.