WO2015096022A1

WO2015096022A1 - Production of a compound comprising at least one carboxylic acid functional group

Info

Publication number: WO2015096022A1
Application number: PCT/CN2013/090286
Authority: WO
Inventors: Pascal Metivier; Yan Zhao
Original assignee: Rhodia Operations SAS
Current assignee: Rhodia Operations SAS
Priority date: 2013-12-24
Filing date: 2013-12-24
Publication date: 2015-07-02
Anticipated expiration: 2016-06-24

Abstract

The present invention concerns a process for the production of a compound comprising at least one carboxylic acid functional group, comprising the reaction of a compound comprising at least one nitrile functional group with nitronium ions.

Description

PRODUCTION OF A COMPOUND COMPRISING AT LEAST ONE CARBOXYLIC ACID FUNCTIONAL GROUP

PRIOR ART

The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of common general knowledge in the field.

Commercially available carboxylic acids are obtained through a limited number of processes which are well known to those skilled in the art. Hence, carboxylic acids are generally produced through oxidation of saturated or unsaturated hydrocarbon substrates such as fatty acid substrates using either a gaseous component such as air and ozone, a nitric acid/metal catalyst component or a combination of both components. Numerous prior art documents disclose variants of such oxidation processes.

Nitriles are readily converted to the corresponding carboxylic acids by a variety of chemical processes, but these processes typically require strongly acidic or basic reaction conditions and high reaction temperatures, and usually produce unwanted byproducts and/or large amounts of inorganic salts as unwanted byproducts.

For instance until now, the traditional methods to produce 2-methylglutaric acid (MGA)from 2-methylglutaronitrile (MGN)are involving strongly acidic or basic reaction conditions in water solution.

It is notably possible to obtain dicarboxylic acids from the conversion of dinitriles by a process consisting in a reaction between nitrile and water in presence of a strong acid such as sulfuric acid and hydrochloric acid. Corresponding carboxylic acids are then produced as well as with 2 equivalent amounts of inorganic salts, such as ammonium salt, ammonium chlorine, ammonium sulfate, and ammonium nitrate.

It is also known to obtain dicarboxylic acids by conversion of the nitrile functional groups to acid functional groups. This process consists in hydrating the nitrile functional groups of the compounds, in order to form amide compounds, and in hydrolyzing the amide functional groups to give carboxyl functional groups, as described in the international application WO2008/062058.

The conversion of the nitrile functional groups to carboxyl functional groups may also be obtained by reaction of the nitrile compounds with a basic hydroxyl compound in solution water, organic solvents, such as ethanol, dioxane, glycol, MeOCH₂CH₂OH ormixture thereof. The ammonia formed is removed and the salt obtained is reacted with an inorganic acid and the diacids formed are isolated and recovered. Such a process is, for example, described in internationalapplicationWO2007/141404. The basic hydroxyl compound is an alkali metal hydroxide, such as sodium hydroxide, potassium hydroxide or the like. However, the corresponding carboxylic acids are produced as salt and it is necessary to proceed with a further treatment.

Because of the general acceptance of these products, the art has been interested in attempts to develop economical and commercially practicable processes for synthesis of the same from available nitrile raw materials and intermediates. In general, the syntheses heretofore proposed are generating important amounts of inorganic salts as unwanted byproducts and have been multi-step processes, necessarily involving a yield of less than the theoretical value at each step, the losses being cumulative such that ultimate yield of carboxylic acid is reduced to a substantial degree.

INVENTION

It appears now that it is perfectly possible to obtain high yield carboxylic acids without generating inorganic or organic salt by reaction a nitrile compound with nitronium ions while avoiding the above identified drawbacks. Process of this invention is a novel route for recovering in value and converting these nitrile compounds or mixture of chemical compounds which can be recovered in value and which are economically advantageous. An object of the present invention is to provide aprocess for the production of such a substance which is simple, which does not involve critical reacting conditions, which is economical, and which provides large yields. This and other objects of the invention will be apparent from the following discussion.

The process further enables the carboxylic acid compound to be produced in a relatively high quantity. The carboxylic acid compounds that are produced can also be relatively easily separated and recovered. The present invention concerns then a process for the production of a compound (A) comprising at least one carboxylic acid functional group, comprising at least the step of mixing at least:

- a compound (N) comprising at least one nitrile functional group, with

- a compound (I) able to produce nitronium ions

The present invention also concerns a process for the production of a compound (A) comprising at least one carboxylic acid functional group, comprising at least the step of reacting at least:

- a compound (N) comprising at least one nitrile functional group, with

- nitronium ions.

The present invention also concerns a compound (A) comprising at least one carboxylic acid functional group susceptible to be obtained by the above identified process.

The present invention also concerns composition comprising at least:

- a compound (A) comprising at least one carboxylic acid functional group obtained by the above identified process, and

- from 0.001 to 0.8 equivalent of salts, preferably from 0.001 to 0.5 equivalent of salts, for 1 equivalent of compound (A); notablyinorganic salts, such as for instance ammonium salt, ammonium chlorine (NH₄C1), ammonium sulfate ((NH4)₂SO₄), and ammonium nitrate (NH₄NO₃), ammoniumfluoride (NH₄F), ammonium bromide( H₄Br), ammonium iodide (NH₄I), ammonium acetate (CH₃COONH₄).

DETAILS OF THE INVENTION

Throughout the description, including the claims, the term "comprising one" should be understood as being synonymous with the term "comprising at least one", unless otherwise specified, and "between" should be understood as being inclusive of the limits.

Definition

As used herein, the term "hydrocarbon group" refers to a group consisting of carbon atoms and hydrogen atoms, which group may be saturated or unsaturated, linear, branched or cyclic, aliphatic or aromatic. Hydrocarbon groups of the present invention may be alkyl groups, alkenyl groups, alkynyl groups, aryl groups and heterocyclic groups.

As used herein, "alkyl" groups include saturated hydrocarbons having one or more carbon atoms, including straight-chain alkyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, cyclic alkyl groups (or "cycloalkyl" or "alicyclic" or "carbocyclic" groups), such as cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl, branched-chain alkyl groups, such as isopropyl, tert-butyl, sec-butyl, and isobutyl, and alkyl-substituted alkyl groups, such as alkyl- substituted cycloalkyl groups and cycloalkyl-substituted alkyl groups. The term "aliphatic group" includes organic moieties characterized by straight or branched-chains, typically having between 1 and 22 carbon atoms. In complex structures, the chains may be branched, bridged, or cross-linked. Aliphatic groups include alkyl groups, alkenyl groups, and alkynyl groups.

As used herein, "alkenyl" or "alkenyl group" refers to an aliphatic hydrocarbon radical which can be straight or branched, containing at least one carbon-carbon double bond. Examples of alkenyl groups include, but are not limited to, ethenyl, propenyl, n-butenyl, i-butenyl, 3-methylbut-2-enyl, n-pentenyl, heptenyl, octenyl, decenyl, and the like.

The term "alkynyl" refers to straight or branched chain hydrocarbon groups having at least one triple carbon to carbon bond, such as ethynyl.

The term "aryl group" includes unsaturated and aromatic cyclic hydrocarbons as well as unsaturated and aromatic heterocycles containing one or more rings. Aryl groups may also be fused or bridged with alicyclic or heterocyclic rings that are not aromatic so as to form a polycycle, such as tetralin. An "arylene" group is a divalent analog of an aryl group. Aryl groups can also be fused or bridged with alicyclic or heterocyclic rings which are not aromatic so as to form a polycycle.

The term "heterocyclic group" includes closed ring structures analogous to carbocyclic groups in which one or more of the carbon atoms in the ring is an element other than carbon, for example, nitrogen, sulfur, or oxygen. Heterocyclic groups may be saturated or unsaturated. Additionally, heterocyclic groups, such as pyrrolyl, pyridyl, isoquinolyl, quinolyl, purinyl, and furyl, may have aromatic character, in which case they may be referred to as "heteroaryl" or "heteroaromatic" groups.

Aryl and heterocyclic including heteroaryl groups may also be substituted at one or more constituent atoms. Examples of heteroaromatic and heteroalicyclic groups may have 1 to 3 separate or fused rings with 3 to about 8 members per ring and one or more N, O, or S heteroatoms. In general, the term "heteroatom" includes atoms of any element other than carbon or hydrogen, preferred examples of which include nitrogen, oxygen, sulfur, and phosphorus. Heterocyclic groups may be saturated or unsaturated or aromatic. Nitronium ions and compound (I)

The nitronium ionNO₂ ⁺ is a reactive cation created by the removal of an electron from the paramagnetic nitrogen dioxide molecule, or the protonation of nitric acid. The reagents to form nitronium ions are notably concentrated nitric acid, fuming nitric acid, or the mixture of nitric acid with sulfuric acid or nitric acid with dehydration agent, like concentrated sulfuric acid, P2O5, glacial acetic acid, and acetic anhydride.

It is perfectly possible to use in the process of the present invention a compound (I) able to produce nitronium ions, notably in the conditions of the reaction. Such a compound (I) is preferably chosen in the group consisting of: nitric acid (HNO₃), dinitrogenpentoxide (N₂0₅) or nitronium salt, such as for instanceNO₂ ⁺ BF₄ ^~, NO₂ ⁺Cl^", NO₂ ⁺ SbF₆ ⁺, and N0₂ ⁺PF₆\

The molar ratio of compound (I) to compound (N) is preferably comprised between 15: 1 and 1 :0.5, notably at the start of the reaction, more preferably comprised between 10: land 1 : 1. Preferably, compound (I) is able to produce a range from 1 to 10 equivalent of nitronium ions, for 1 equivalent of nitrile function, notably in the conditions of the reaction.

Preferably, compound (I) is nitric acid and the process of the invention concerns then a process for the production of a compound (A) comprising at least one carboxylic acid functional group comprising the reaction of a compound (N) comprising at least one nitrile functional group with a range from 1 to 10 equivalent of nitric acid (HNO₃) for 1 equivalent of nitrile function.

Reaction with nitric acid may be expressed as follows:

R-CN + HNO₃ -> R-COOH + N₂O

The nitric acid employed may vary fairly widely in strength and purity. In case of nitric acid used as compound (I), nitric acid preferably provides a concentration comprised between 80and 99.9% in water, more preferably comprised between 85and 99%.

It's perfectly possible according to the present invention to add an othercompound able to increase the acidity of the reaction medium in order to raise the generation of nitronium ions, such as for example by addition ofan acid, in the reaction medium, chosen in the group consisting of: sulfuric acid, acetic acid, acetic anhydride or hydrochloric acid. We may cite for this purpose the mixture as follows: HNO₃/H₂SO₄, HN0₃/acetic acid, HN0₃/acetic anhydride, HN0₃/HC1, HNO₃/HF, HNO₃/HI, and HNO₃/HBr. Addition of acid to the reaction medium may be carried out at the start of the reaction.

Indeed, although concentrated nitric acidproduces the nitronium ion by itself, the equilibrium is so far to the left that the process is slow. Adding acid, such as sulfuric acid, to the reaction mixture increases the concentration of the nitronium ion, thereby increasing the rate of the nitration reaction.

For the determination of the nitric acid, the state of the art provides different analyzing methods from the field of titration, NIR- spectroscopy, UV spectroscopy/photometry, and chromatography. One can notably titrate nitric acid in acid mixtures by using organic solvents, such as acetone, as titrant instead of water. Another possibility for the determination of the nitric acid by means of titration consists in that, in addition to the titration of the acids with lye, a second titration using a solution of lanthanum salt as titrant is performed for the measurement of the sum of the fluoride containing compounds. The content of nitric acid can be determined by way of netting the results of both titrations.

Preferably, the reaction medium provides at the start of the reaction aH⁺ ions concentration ([H⁺]) superior or equal to 11 mol/L, ie per litre of the total reaction medium.

Process of the present invention may also comprise a source of water that may be for instance H₂O, H₂O₂ or nitric acid.Addition of the source of water to the reaction medium may be carried out at the start of the reaction or during the reaction for instance.

Preferably, the molar amount of acid compounds in the reaction medium is superior or equal to the molar amount of water, notably at the start of the reaction. Molar amount of acid compounds may express for instance the sum of molar amount of nitric acid and the molar amount of acid compound able to increase the acidity of the reaction medium, such as for example sulfuric acid, such as concentrated sulfuric acid, acetic acid or glacial acetic acid, acetic anhydride or hydrochloric acid.

The source of water,that may be necessary for the hydration reactions of the nitrile functional groups and the hydrolysis of the amide functional groups,may be added at the beginning of the hydration reaction. Thus, the amount of water added is advantageously between 1 and 20 mol of water per nitrile functional group to be hydrated, preferably from 1 to lOmol of water per nitrile functional group to be hydrated.

Compound (N) comprising at least one nitrile functional group

Compounds (N) comprising at least one nitrile functional group may notably comprise one, two or three nitrile functional groups.

Said compounds (N) may comprise a straight, branched or cyclic hydrocarbon group, that may be for example an alkyl, alkenyl, aryl, cycloalkyl or heterocyclic group, optionally comprising one or several heteroatoms such as O, S, F, and N. Preferably, compound (N) comprises from 2 to 10 carbon atoms. Compound (N) may be for instance an aliphatic a, ω-dinitrile.

Mention may be made, as compounds (N) suitable for the process of the invention, of methylbutyronitrile, valeronitrile, 2-methyl-2-butenenitrile, 2-pentene-nitrile, 3-pentenenitrile, 4-pentenenitrile,

2-methyl-3-butenenitrile and dinitriles, such as 2-methylbutyro-nitrile, methylglutaronitrile, ethylsuccinonitrile, succinonitrile, glutaronitrile, adiponitrile or analogous products, or a mixture of at least two of the said compounds.

Compounds (N) comprising at least one nitrile functional are either commercially available, may be prepared by known procedures or otherwise may be prepared using conventional chemistry knowledge.

According to a particularly favoured form, the nitrile compounds suitable for the invention are the dinitrile compounds formed in the process for the hydro cyanation of butadiene, more particularly the branched dinitrile compounds, such as methylglutaronitrile and ethyl-succinonitrile, alone or as a mixture; the carboxylic acids recovered are either methylglutaric acid or a mixture of methylglutaric acid, ethylsuccinic acid and adipic acid.

As it is possible to use a mixture of compounds (N) the process of the invention thus makes it possible to produce a mixture of carboxylic acid compounds. Compound (A) comprising at least one carboxylic acid functional group

Compounds (A) may notably comprise one, two or three carboxylic acid functional groups.

Said compounds (A) may comprise a straight, branched or cyclic hydrocarbon group, that may be for example an alkyl, alkenyl, aryl, cycloalkyl or heterocyclic group, optionally comprising one or several heteroatoms such as O, S, F, and N. Preferably, compound (A) comprises from 2 to 10 carbon atoms. Compound (A) may be for instance an aliphatic a, ω-dicarboxylic acid.

Mention may be made, as compounds (A) chosen in the group consisting of: 2-methyl butyric acid,n-valeric acid,2-methylbut-2-enoic acid,pent-2-enoicacid, pent-3-enoicacid, pent-4-enoicacid,

2-methylbut-3-enoic acid,2-methylsuccinic acid,2-methylglutaric acid, 2-ethylsuccinic acid,succinic acid,glutaric acid, adipic acidor analogous products, or a mixture of at least two of the said compounds.

Other examples of dicarboxylic acids include, but are not limited to, oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, malic acid, tartaric acid, aspartic acid, glutaric acid, glutamic acid, glutaconicacid, adipic acid, muconic acid, suberic acid, itaconic acid, and terephthalic acid. Examples of tricarboxylic acids include, but are not limited to, citric acid, isocitric acid, aconitic acid, propane- 1,2,3-tricarboxylic acid, and trimesic acid.

The preferred reactions involved in the process of the present invention are notably the following:

2-methylglutaronitrile and nitric acid to produce 2-methylglutaric acid and N₂O

2-methylglutaronitrile and nitric acid and sulfuric acid to produce 2-methylglutaric acid and N₂O

Parameters of the process

Notably, the process of the present invention comprises at least the step of heating a blend of at least compound (N) and compound (I) as previously defined. Temperature of the reaction may be comprised between 20°C and 120°C, preferably between 30°C and 110°C, more preferably between 50°C and 100°C.

Reaction time is preferably comprised between 30 minutes and 20 hours. The exact residence time will generally be chosen so that a satisfactory space/time efficiency is achieved. The process of the invention can be carried out batchwise or continuously. The reaction can be effected in fixed bed reactors, stirred reactors, fluidized bed or transport reactors, gravity flow moving bed reactors or any other conventional mode for reactions.

In a continuously process, the reaction may be carried out in a single plug-flow reactor or in several stirred reactors arranged in series. The reaction is advantageously carried out in a device comprising two successive and separate reaction regions, a first region operating under stirred conditions and a second final region operating under plug-flow conditions. The presence of these two reaction regions makes it possible to obtain complete conversion of the nitrile functional groups to carboxyl functional groups. This complete conversion makes it possible to facilitate the recovery and separation of the carboxyl compounds, in particular when the nitrile compounds to be converted are dinitrile compounds, and thus to avoid the presence of cyano and/or amide compounds in the final reaction medium. Thus, the process can be carried out in a device comprising a stirred reactor, equipped with a condenser in order to obtain reflux and a device which recovers the ammonia formed, and a plug-flow reactor arranged in series with the stirred reactor. The first stirred reactor can advantageously be a loop reactor, comprising an internal circulation loop and an external circulation loop. A heat exchanger is advantageously provided on the external circulation loop. Of course, other types of stirred reactors may be used. Advantageously, the temperatures and the pressures in the stirred reactor and the plug-flow reactor can be different. The plug-flow reactor advantageously operates adiabatically. Preferably, the reaction temperature in the plug-flow reactor is higher than that present in the stirred reactor.

In the case of a batchwise process, the operating conditions of the reactor are determined in order to advantageously obtain a degree of conversion of the nitrile functional groups reaching 100%.

At the end of the reaction, it is possible to separate the various compounds by the usual techniques, such as distillation, crystallization or liquid/liquid extraction; though in numerous applications, the mixture of compounds can be used without separation.

Use of nitric acid as reactant involved in the process of the invention notably leads to the production of nitrous oxide or various NO_x compounds. The term "NO_x compounds" as used herein relates to nitrogen oxides, nitroso gases or nitrogen oxides, and therefore refers to gaseous oxides of nitrogen. On hand, they are abbreviated by NO_x, since several nitrogen-oxygen-compounds exist, such as N₂O, NO, N₂O₃, NO₂, N₂O₄, N₂O₅, because of the many oxidation states of nitrogen.

Likewise, the compounds (A) as obtained are advantageously used as such or in the form of a mixture in, for example, the manufacture of polyurethanes, polyesters, polyamides or the like.

Other details and advantages of the invention will become more clearly apparent in the light of the examples given below solely by way of illustration.

EXPERIMENTAL PART

Example 1

44g of fuming nitric acid (>95%) was charged in 100ml flask, and heated to 60°C, 10.8g MGN was added slowly by dropping, control the inner temperature between 60-100°C. Gas was formed during the dropping time. After the addition of MGN, the mixture was stirred at 60°C for 30minutes. All reaction mixture was expelled a current of N₂ to remove the most of nitric acid, then water was added, and the mixture was concentrated in vacuum to afford 14g of colorless oil (MGA, yield: 96%), trace NH₄NO₃ was formed (0.02eq compare to MGA).

1H NM (400MHz, DMSO-<½): 1.05 (d, J=6.8Hz), 1.55-1.58 (m, 1H),

1.71-1.78 (m, 1H), 2.33-2.50 (m, 3H), 6.97-7.22 (t, 0.16H, NH₄ ⁺)

¹³C NMR (400MHz, DMSO-i 6): 17.27, 28.75, 31.82, 38.41, 174.55,

177.47

Example 2

9.78g of nitric acid (90%) and 2.26g MGN were charged in 50ml flask, and heated to 90°C slowly. Gas was formed. The mixture was stirred at 90°C for 16 hours. After reaction, most of the nitric acid was removed from the mixture, then water was added, and the mixture was concentrated in vacuum to afford the mixture of MGA (yield: 98%, determined by 1H NMR) and NH₄N0₃ (0.3eq compare to MGA).

1H NMR (400MHz, DMSO- 6): 1.05 (d, J=6.8Hz), 1.55-1.58 (m, 1H), 1.71-1.78 (m, 1H), 2.33-2.50 (m, 3H), 6.97-7.22 (t, 2.4H, NH₄ ⁺)

Example 3

108mg MGN, 278mg of 68% nitric acid and 392mg of H₂SO₄(98%) were charged in 5ml tube , and heated to 60°C for 3 hours, then heated to 90°C for 8 hours, the reaction was followed by NMR. After reaction, water was added, 96% yield of MGA was formed, and 0.2eq ammonium salts (mixture of (NH4)₂SO₄ and NH₄NO₃) were formed compare to MGA. 1H NMR (400MHz, DMSO-<½): 1.05 (d, J=6.8Hz), 1.55-1.58 (m, 1H), 1.71-1.78 (m, 1H), 2.33-2.50 (m, 3H), 6.97-7.22 (t, 1.6H, NH₄ ⁺)

Example 4

108mg MGN, 186mg of 68% nitric acid and 196mg of H₂SO₄(98%) were charged in 5 ml tube , and stirred at 90C, the reaction was followed by NMR.After 16h, the reaction was completed, water was added and 98% yield of MGA was formed, and 0.2eq ammonium salts (mixture of (NH4)₂SO₄ and NH₄NO₃) were formed compare to MGA by NMR.

1H NMR (400MHz, DMSO-i 6): 1.05 (d, J=6.8Hz), 1.55-1.58 (m, 1H), 1.71-1.78 (m, 1H), 2.33-2.50 (m, 3H), 6.97-7.22 (t, 1.6H, NH₄ ⁺)

Example 5

108mg MGN, 372mg of 68% nitric acid and 196mg of H₂S0₄(98%) were charged in 5 ml tube , and stirred at 90C, the reaction was followed by NMR.After 16h, the reaction was completed, water was added and 98% yield of MGA was formed, and 0.5eq ammonium salts (mixture of (NH4)₂SO₄ and NH₄N0₃) were formed compare to MGA by NMR.

1H NMR (400MHz, DMSO-<½): 1.05 (d, J=6.8Hz), 1.55-1.58 (m, 1H), 1.71-1.78 (m, 1H), 2.33-2.50 (m, 3H), 6.97-7.22 (t, 4H, NH₄ ⁺)

Example 6

108mg MGN, 186mg of 68% nitric acid and 294mg of H₂S0₄(98%) were charged in 5 ml tube , and stirred at 90C, the reaction was followed by NMR. After 16h, the reaction was completed, water was added and 98% yield of MGA was formed, and 0.2eq ammonium salts (mixture of (NH4)₂S0₄ and NH₄N0₃) were formed compare to MGA based on NMR. 1H NMR (400MHz, DMSO-<½): 1.05 (d, J=6.8Hz), 1.55-1.58 (m, 1H), 1.71-1.78 (m, 1H), 2.33-2.50 (m, 3H), 6.97-7.22 (t, 1.6H, NH₄ ⁺)

Comparative example 1

2.2g of MGNand 5.4g of 80% H₂SO₄were charged in 25ml flask , and heated to 90°C for 16 hours, the reaction was followed by1H NMR. After reaction, water wasadded and two phase separation, 98% yield MGA was obtained, and leq (NH₄)₂SO₄ was formed compare to MGA.

1H NMR (400MHz, DMSO-<½): 1.05 (d, J=6.8Hz), 1.55-1.58 (m, 1H), 1.71-1.78 (m, 1H), 2.33-2.50 (m, 3H), 6.97-7.22 (t, 8H, NH₄ ⁺)

Results of the previous examples are mentioned in the following Table.

We can observe then that process according to the present invention involving reaction of nitric acid leads to an important reduction of salt content in the final products compared to the classical known process, while keeping a high yield and conversion of nitrile compound.

Claims

1. A process for the production of a compound (A) comprising at least one carboxylic acid functional group, comprising at least the step of mixing at least:

- a compound (N) comprising at least one nitrile functional group, with

- acompound (I) able to produce nitronium ions.

2. The process according to claim 1 wherein compound (I) is chosen in the group consisting of: nitric acid, dinitrogenpentoxideor nitronium salts.

3. The process according to claims 1 to 2 wherein the molar ratio of compound (I) to compound (N) is comprised between 15: 1 and 1 :0.5.

4. The process according to anyone of claims 1 to 3 wherein compound (I) is able to produce a range from 1 to 10 equivalent of nitronium ions, for 1 equivalent of nitrile function.

5. The process according to anyone of claims 1 to 4 wherein compound (I) is nitric acid and wherein concentration of nitric acid is comprised between 80and 99.9% in water.

6. The process according to anyone of claims 1 to 5 wherein an acid is further added to the reaction medium.

7. The process according to claim 6 wherein acid is chosen in the group consisting of: sulfuric acid, acetic acid, acetic anhydride or hydrochloric acid.

8. The process according to anyone of claims 1 to 7, wherein the reaction medium provides at the start of the reaction a H⁺ions concentration superior or equal to 11 mol/L, ie per litre of the total reaction medium.

9. The process according to anyone of claims 1 to 8, wherein the reaction medium also comprisesa source of water.

10. The process according to claim 9, wherein the molar amount of acid compounds in the reaction medium is superior or equal to the molar amount of water.

11. The process according to anyone of claims 1 to 10 wherein compound (N) comprises a straight, branched or cyclic hydrocarbon group, optionally comprising one or several heteroatoms such as O, S, F, and N.

12. The process according to anyone of claims 1 to 11 wherein compound (N) is an aliphatic a, ω-dinitrile.

13. The process according to anyone of claims 1 to 12 wherein compound (A) an aliphatic a, co-dicarboxylic acid.

14. The process accordingto anyone of claims 1 to 13 whereintemperature of the reaction may be comprised between 20°C and 120°C.

15. A process for the production of a compound (A) comprising at least one carboxylic acid functional group, comprising at least the step of reacting at least:

- a compound (N) comprising at least one nitrile functional group, with

- nitronium ions.

16. A composition comprising at least:

acompound (A) comprising at least one carboxylic acid functional groupobtained by the process according to anyone of claims 1 to 15; and from 0.001 to 0.8 equivalent of salts, for 1 equivalent of compound (A).