DE1189964B - Process for the production of dinitro alcohols - Google Patents

Description

Process for the production of dinitro alcohols The invention relates to an economical process for the production of dinitro alcohols of the general formula in which R is hydrogen, a lower aryl group, a monocyclic alkyl group or a lower hydroxylalkyl group and R 'is hydrogen or the methyl group, by adding an alkali metal hydroxide and an alkali metal nitrite stepwise to a mixture of a lower alkanal having the general formula and a nitro compound of the general formula in which R and R 'are groups of the type indicated above, and the nitro complex obtained is added to a silver nitrate solution, and is characterized in that while the nitrite complex is treated with the silver nitrate solution, the pH value is in the range from about 4 to 5' will.

So far, polyvalent nitro alcohols have been oxidized by laboratory Nitration hentellt This process gives equal yields for small quantities and is very easy to implement.

However, if the procedure is to be carried out with larger eyes, so the yield decreases at amounts of z. B. 250 g far below the ftine application of the process in practice.

For the production of polyvalent crude alcohols, the essentially the foide process used: A mononitro compound is combined with alihydroxide, for example, sodium hydroxide or canahydroxide is converted into its acis salt, which is nitrite forms a complex. A solution will be found for this complex as soon as possible of silver nitrate added and after removal of the precipitated metallic silver separating the reaction product from the reaction mixture. The reaction product yields however, decrease very sharply as soon as the reaction amounts are increased. This is to the physical limitation in the rate of addition of the silver nitrate traced back. In the present invention it has now been found that satisfactory Yields are obtained that are far above the previous ones if the following modified procedure is applied.

It was found that to achieve better yields Reaction must be carried out in a limited pH range, and that must be the pH range between 4 and 5. In the method used so far, there were such Reaction conditions especially when carrying out the process on a large scale unreachable. The pH value of the aci salt of the nitro compound was the same as before Procedure to start the reaction usually between 8 and 10, and he was too not significantly reduced by the addition of sodium nitrite. The addition of Silver nitrate solution, which normally has a pH range of 4 to 5, causes a progressive change in pH from a high to a low value; unless the silver nitrate can be added all at once, whereby a rapid drop in pH to a low value would occur. This was not possible with the older method. Rather, the reaction proceeded in the pH range between 5 and 10, with only a small part of the reaction in to the lower pH range, so that naturally only one under these conditions low yield was achieved.

According to the present invention, there are improvements in the The method is to adjust the pH to between 4 and 5 during all reaction stages keep. In this process, the complex mixture of the acinitro salt and the sodium nitrite added to the silver nitrate solution, which has a pH between 4 and 5 has. Instead, the previous method used the silver nitrate solution added to the complex mixture of aci salt and sodium nitrite, the system naturally was outside the specific pH range. With the new process, the reaction begins already at a pH range of 4 to 5 and becomes complete carried out at this pH. Due to the low pH value, the reaction is completed in a relatively short time, and yields are obtained which are much greater than those obtained so far procedures carried out.

The reaction carried out in these processes is that forming a nitroaliphatic compound with sodium or potassium hydroxide of the corresponding acimetal nitro salt reacts.

The added sodium nitrite solution forms a complex mixture with the sodium acinitol salt. The sodium nitrite-sodium acinitol salt mixture is then added to a solution of silver nitrate with continued stirring. The reaction is best represented by the following equation: In the equation, R can be hydrogen, any lower alkyl radical, a cycloaliphatic radical, or a functional group-substituted derivative of one of these radicals.

In the case where the manufacture of a polyhydric nitro alcohol with the formula Should it be desired, this can be done by gradually adding an alkali metal hydroxide and an alkali metal nitrite to a mixture of a lower alkanal having the formula and a nitro compound having the formula take place, where R in the above formulas such radicals as hydrogen, lower alkyl, monocyclic alkyl or lower hydroxyalkyl radicals, and R 'denotes hydrogen or a methyl radical.

The nitrite complex obtained is then dissolved in a silver nitrate solution while maintaining the pH in the range of about 4 to 5.

The reaction can best be carried out using a special manufacturing process for a special connection with a detailed explanation of the nature of the Reaction to be described.

Example of those in the present invention as starting materials Nitro compounds used are nitroethane and nitroethane. production of dinitro-l-propanol A mixture of 1 mole of nitroethane and 1 mole of formaldehyde is placed in a three-necked reactor vessel given and cooled to -5 "C. A solution of 1 mol of atrium hydroxide in water is used Poured into the bottle while maintaining the temperature between 0 and 5 "C. After the mixture has been stirred for 1 hour or a longer period of time, 1 mol of sodium t dissolved in water is added and the mixture for 15 minutes at 0 ". This mixture is then a solution of 2 moles of silver nitrate in water added, the temperature of the silver nitrate solution being kept at 0 ° C. It educates a white precipitate that disintegrates in a few seconds and a metallic one Oil layer is deposited. During this period the temperature can rise up to After one hour of continued stirring, temperature between 20 "C increase and 25 "C is kept. The precipitate is filtered out and solution with ether or other suitable solvents. The ethereal solution is evaporated, whereby 2,2hitro-1-propanol remains as a residue. The starting point of this connection is 850C. The yield was 770 per cent of the theoretical value.

Preparation of 2,2-dinitro-1,3-propanediol ie mixture of 1 mol Nitromethane and 2 moles of Fdaldehyde in water are cooled to -5 "C, like in a three-necked Reactor vessel, as used above, is used for thorough mixing. One Solution of 1 mole of sodium oxide in water is added to the bottle while the temperature to 0 ° C. after the addition and the stirring after the addition is complete Hour continues.

A solution of 1 mol of rium nitrite in water is added to this solution and the mixture was stirred at 0 ° C for minutes. The one prepared in this way mixture is then placed in a solution of 2 moles of silver nitrate in water, the temperature being maintained at approximately 0 ° C during the addition.

The addition is carried out with vigorous stirring, and a white precipitate may appear can be observed, which disintegrates after its formation and a metallic silver deposit leaves behind. Stirring is continued for 1 hour and the mixture then becomes filtered off by the silver. The resulting yellow solution is five times with ether or extracted other solvents, or the extraction can be carried out continuously will. At the end of the extraction, the ether is removed by evaporation. The residue is made by azeotropic distillation using methylene chloride as the azeotropic Medium dehumidified. This begins after a sufficient amount of water has been removed 2,2-Dinitro-1,3-propanediol to crystallize out. The average yield is in in this case between about 55 and 60 percent by weight, based on the weight of the used nitromethane. The melting point of the material obtained in this way was between 145 and 148 "C. The density of 2,2-dinitro-1,3-propanediol is d25 = 1.54.

An advantage of the new method is that during the process there is no significant loss of expensive silver, as it is not necessary to transform the precipitated silver back into crystallized silver nitrate. That Rather, precipitated silver is dissolved in an excess of HNO3 and then the pH adjusted to 4 by adding a suitable hydroxide. In this way the silver can be used again in the next batch.

The new method enables a connection to be established such as 2-2-dinitropropanol or 2,2-dinitro-1,3-propanediol in large quantities and with good amounts Exploit. Previously, attempts to make these compounds required a cumbersome one Process, and the final yield was usually economical to run too low.

According to the new method, all of the above-mentioned difficulties will be solved and it now becomes an easy and quick process proposed making polynitro compounds on a large scale at low cost can be produced.

Claims (2)

Claims: 1. Process for the preparation of dinitro alcohols of the general formula NO2 OH RC-CH-R 'NO2 in which R is hydrogen, a lower alkyl group, a monocyclic alkyl group or a lower hydroxylalkyl group and R' is hydrogen or the methyl group, by adding one Alkali metal hydroxide and an alkali metal nitrite gradually to a mixture of a lower alkanal having the general formula and a nitro compound of the general formula wherein R and R 'are groups of the type indicated above, and the nitro complex obtained is then added to a silver nitrate solution, characterized in that the pH is kept in the range from about 4 to 5 during the reaction of the nitro complex with the silver nitrate solution. 2. The method according to claim 1, characterized in that 2,2-dinitro-1-propanol or 2,2-dinitro-1,3-propanediol is produced. References considered: U.S. Patent No. 2,522 959; Chemisches Zentralblatt, 1954, pp. 4598 to 4599.