DE2113338C3 - Process for the alkoxylation of carboxamides alkylated on the nitrogen - Google Patents

Description

wherein R ₁ and R _{2 are} independently hydrogen, methyl or ethyl groups or are linked together by an alkylene group with 2 to 6 carbon atoms or an alkyl-substituted alkylene group with 2 to 6 carbon atoms and Q to Q alkyl groups and R ₃ Denotes hydrogen or an alkyl group with 1 to 6 carbon atoms, with alcohols of the general formula (11)

R ₄ (OH). (H)

wherein R ₄ . an alkyl or alkylene group with

1 to 4 carbon atoms and π 1 oust 2 means, by electrolysis of the nitrogen-alkylated carboxamides (I) with the alcohols (II) in the presence of a conductive salt, characterized in that the conductive salt used is ammonium or alkali hexafluorophosphate, tetrafluoroborate or - perchlorate or a Tetrsalkylar ".moniumtetrafluoroborat with Q to C ₆ -Alkrlgruppen in a concentration of 0.01-5.0 mol / l, preferably 0.1-

2 mol / l is used and that the electrolysis is carried out at temperatures between +10 and 100 ^° C., preferably between 30 and 80 ^° C.

out that in the implementation of N-alkylcarboxamides with acetals or hemiacetals in the presence of organic sulfonic acids as acidic catalysts at temperatures between 50 and 150 "N - λ - alkoxyalkylcarboxamides are formed (DTPS 1273533).

It has now been found that the alkoxylation of carboxamides of the general formula (I) alkylated on nitrogen

The invention relates to a process for the electrochemical alkoxylation of nitrogen alkylated carboxamides with alcohols in the presence of conductive salts.

It is known that in the electrolysis of N ₁ N-Dimethylcarbonsäureamiden and an aliphatic alcohol in the presence of nitrate are formed as conducting salt N-alkoxymethyl-N-Methylcarbonsäureamide (US-PS 34 59 643). According to this process, dimethylformamide, acetamide and benzamide were electrolyzed with monohydric aliphatic alcohols with one to six carbon atoms in the presence of ammonium nitrate as the conductive salt. The alkoxylation takes place on the methyl group adjacent to the nitrogen with the simultaneous formation of molecular hydrogen.

N-alkoxyalkyl-N-methylcarboxamides can can also be produced chemically in a multistage process by firstly producing a mixture of N-methylcarboxamide with paraldehyde in the presence of sodium hydroxide heated to solution and then slowly an aliphatic alcohol with cooling is added (U.S. Patent 2,449,332). Is known further-

(D

CH ₂ -R ₃

wherein R ₁ and R ₂ independently of one another are hydrogen,

Mean methyl or ethyl groups or together

by an alkylene group with two to six carbon atoms

or an alkyl-substituted alkylene group of two

up to six carbon atoms and C ₁ - to Q-alkyl groups,

are connected and R _{3 is} hydrogen or an alkyl

means group with one to six carbon atoms, with alcohols of the general formula (Ii)

R ₄ (OH) _n

(II)

jo in which R _{4 is} an alkyl or alkylene group with 1 to 4 carbon atoms and η 1 or 2, by electrolysis of the nitrogen-alkylated carboxamides (I) with alcohols in the presence of a rope salt is particularly advantageous when ammonium is used as the conductive salt - Or alkali hexafluorophosphate, tetrafluoroborate or perchlorate or a tetraalkylammonium tetrafluorate with C ₁ - to Q-alkyl groups in a concentration of 0.01-5.0 mol / l, preferably 0.1-2 mol / l, and if one, durchfuhrt the electrolysis at temperatures between +10 and 100 ⁰ C, preferably between 30 and 80 ° C.

The possibility according to the invention of using the new conductive salts mentioned was extraordinary Surprising, since it was previously of the opinion that for electrochemical alkoxylations more organic Compounds the presence of nitrate ions is crucial (cf. the US-PS mentioned at the beginning 34 59 643 and J. Am. Chem. Soc. 88 [1966], p. 4657- 4660 and Acta Chem. Scaiid. 24 [1970], pp. 473-481). The process according to the invention gives alkoxylated N-mono- or N.N-dialkyl-carboxamides the general formula (IH)

R ₁ -CN
O

(IH)

CH-Rj

GR ₄ - (OH) _n .,

wherein R ₁ , R ₂ , R ₃ and R _{4 have} the meanings given above.

Furthermore, in the electrolysis of N-monoalkylcarboxamides and alkanediiols N, N'-di-

alkoxyalkylene-bis-carboxamides of the general Formula (IV)

H H

R ₁ -C- / Vc-R ₁

O CH-O-Rj ₁ -O-CH O

R ₃ R ₃ (IV)

formed, wherein R, and R _{3 have} the abovementioned meaning and R _{6 is} an alkylene group having 1 to 4 carbon atoms.

Finally, in the electrolysis of N ₁ N-dialkylcarboxamides and alkanediols, N ₁ N'-dialkoxy-alkylene-bis-KN'-dialkylcarboxamides of the general formula (V)

O CH-OR ₆ -O-CH O

R ₃ R ₃ (V)

wherein R ₁ , R ₂ , R ₃ and R _{4 have} the abovementioned meaning, and cyclic Ν, Ν-dialkoxyalkylenecarboxamides of the general formula (VI)

R ₅ -O

R ₁ -CN R ₆

Il \ /

CH-O

(VI)

R,

formed, wherein R ₁ , R ₃ and R _{6 have} the abovementioned meaning and R _{5 is} a methylene or ethylene group or R and R _{5 are} linked together by an alkylene or alkyl-substituted alkylene group having two to six carbon atoms and Q-alkyl groups are.

As N-mono- or NN-dialkylcarboxamides there are mainly N-methylformamide, N-ethylformamide, N, N-dimethylformamide, NN-diethylformamide, N-methylacetamide, N-ethylacetamide, N ₁ N-dimethylacetamide, Ν, Ν-diethylacetamide, N-methyl-N-ethylacetamide, N-methylpropionamide, N-ethylpropionamide, 1,4-dimethylacetidinone-2, 1,4,4-trimethylacetidinone-2, 1-ethyl-1-methyl-acetidinone-1-methylpyrrolidone-2 and I. -Athylpyrrolidon-2 in question.

Suitable alcohols are aliphatic primary, secondary or tertiary alcohols with 1 to 4 carbon atoms, such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol and tert-butanol, and, as alkanediols, ethylene glycol, 1,2 - and 1,3-propanediol, 1,2-,! 3-, 2,3- and 1,4-butanediol <A &

Suitable electrolyte salts for the process are ammonium and alkali metal hexafluorophosphates, tetrafluoroborates or perchlorates or tetraalkylammonium tetrafluoroborates with C _{1 to C 6} alkyl groups.

The electrolyte salts used are preferably potassium or ammonium thermophosphate, sodium, ammonium or tetramethylammonium tetrafluoroborate and ammonium or potassium perchlorate.

The electrolyte salts are added to the electrolysis solution in concentrations of 0.01 to 5 mol / l, preferably from 0.1 - in particular from 0.8 - to 2 mol / l added.

The electrochemical alkoxylation is carried out batchwise or continuously. In the discontinuous process, the electrolysis can be carried out, for example, in the electrolysis cell 1 shown in the figure. It has a tightly fitting lid 2 through which the power lines for the electrodes 3 and 4 are passed and in which the openings 5 for the inlet of the electrolysis solution 6 for the discharge of the gas and 9 for a thermometer are located. The opening for the discharge of the gas may be provided with a reflux condenser, in the evaporating portions of the Elektrolyseinischung with a brine fluid to -130 ⁰ C, may be preferably ⁰ to -30 C, recondensed. The two electrodes 3 (anode) and 4 (cathode) are arranged at a distance of 0.1 to 5 ^ mm, preferably 0.5 to 20 mm, from one another. Meshes or sheets made of palladium or platinum as well as metal electrodes, preferably titanium electrodes, coated with precious metal or mixed oxide are used as electrode material.The mesh-shaped design of the electrodes is particularly advantageous because hydrogen gas formed during electrolysis is more easily discharged and, in addition, the solution is evenly mixed is supported. The vertical arrangement of the electrodes can also be replaced by a horizontal one. An arrangement of several pairs of electrodes is also possible, which has proven particularly useful in the block-like combination of angled or non-angled capillary gap electrodes. In a preferred embodiment of these electrode pairs combined in a block-like manner, the electrode spacing has been enlarged towards the outside. The electrolytic cell is encased and can be connected to a heating or cooling liquid circuit through the inlet 7 and outlet nozzles 8. The temperature of the electrolysis solution is monitored by a thermometer 9 or a thermal sensor and controlled by heating or cooling. The working temperature chosen for the electrolysis is a temperature which is below the boiling point of the lowest boiling reactant and above the melting point of the highest melting reactant. There were temperatures of 10 to 100 ⁰ C, preferably of 30-80 ° C, applied. The anode current density was 3-6 A / dm, preferably 5.2-5.6 A / dm ² .

Fiat lower current density is possible, but it slows down product formation. A current density higher than 6 A / dm ² results in excessive heating of the electrolysis solution. During the electrolysis, the solution is mixed vigorously either by a stirrer, for example magnetic stirrer 10, or by pumping.

so the electrolysis solution consists of equimolar Mixtures of an N-mono- or Ν, Ν-dialkj'lcarboxamide, in which a conductive salt has previously been dissolved, and an alcohol. The leitsaz can, however, if it does is less soluble in the carboxamide, can also be dissolved in the alcohol. The electrolysis solution can initially contain an excess of alcohol of up to 10% by weight of the equimolar amount of alcohol. It can also be beneficial after the half expired

Add a small amount of alcohol again during the electrolysis period. The procedure can be in terms of Energy or material yield can be optimized. It has been shown to be beneficial, but not electrolysis to carry out until complete conversion of the reactants, because the product formation Cell voltage increases, with the material and energy yield falling.

If the process is operated continuously, there is a in the cover 2 of the electrolysis vessel 1 a further opening is provided for the continuous pumping of the electrolysis solution.

From the electrolyte solution pumped around in the circuit, a part is used for product processing severed. After checking the content of the electrolyte solution for the ratio of product formation to Starting material with the help of a gas chromatographic or a nuclear magnetic resonance spectroscopic

A'tn I nr · «

K UWJUIIf

Passed reflux condenser, which is cooled to - IO C. The products that condense in the process flow back into the electrolyte solution. After passing one The experiment was terminated with current equivalents of 1,202 Faraday. After removing the conductive salt the analysis of the electrolyte solution in mole percent showed:

N-methoxymethyl-N-methylforniamide 85 "ι.

N.N-Dimethylformamide 8 ""

Methanol 7%

This corresponds to a current efficiency of 80.5 "π (based on the N.N-dimethylformamide) and one Energy expenditure of 0.96 kWh mol of product.

At spie! I.

In the electrolysis cell described in Comparative Example 1, a mixture of 39.9 g of NN-Di-! TieihvlformüfTiid and! 9.2 ^M methanol is under "usi *". ^7th

Before the products can be separated by distillation, for example, acidic guide tubes must be removed from the solution separated by ion exchangers or shaking with water or ether. In the presence of acidic conductive salts, the products formed are partly destroyed again during work-up.

The raw materials recovered in the distillation after they have been adjusted to the required molar ratio metered in again with a conductive salt of the continuously circulating electrolysis solution.

The electrolysis is normally carried out at normal pressure. But it can also be reduced Pressure; between 300 and 400 Torr can be operated. To avoid the formation of explosive Gas mixtures of hydrogen and air is the admixture of an inert gas, for example nitrogen, advantageous.

Those produced by the electrochemical process alkoxylated N-mono or N.N-dialkylcarboxamides are valuable polar, non-aqueous solvents for electrolysis. As a solvent they are also used for spinning threads. Those alkoxylated in the \ position to the nitrogen atom Carboxamides are also intermediate products for the preparation of N-alkylene- or N-alkylene-N-alkvlcarboxamides. The cyclic carboxamides alkoxylated in the t-positions to the nitrogen are intermediate products for the production of N-alkylene lactams. They are also used as additives in the manufacture of plastics, for example polyamides, used.

Comparative example 1

A mixture of 39.9 g NN-dimethylformamide and 19.2 g methanol with the addition of 4.8 g ammonium nitrate is poured into an electrolysis cell 1 (see figure) with a capacity of about 70 ml with cover 2 and reflux condenser. Two concentrically arranged platinum mesh cylinders with 225 meshes per one ² and with! 0 or 30 mm 0 at a height of 50 mm are immersed in the solution as electrodes. The cathode is inside. The temperature during the electrolysis is kept at 50 "C. After switching on the electrolysis current, the anode current density is 5.4 A / dm ² and the electrolysis voltage is 9.5 volts. Stirring is carried out by magnetic stirrers at 30-35 rpm. The cell is under normal pressure Gases escaping through the gas outlet are filled with a: ii of 9.8 g of potassium hexafluorophosphate. The temperature during the electrolysis is kept at 50 ° C ". After switching on the electrolysis current, the anode current density is 5.4 A dm ² and the electrolysis voltage is 8.0 volts. The stirring takes place. <-, by magnetic stirrer with 30 to 35 llpm. The cell is under normal pressure. The gases escaping through the gas outlet are gelated through a reflux condenser. who is chilled to - IOC. The products that condense in the process flow back into the electrolyte solution. The experiment was terminated after a current equivalent of 1,202 Faraday had passed. After removing the citric salt, the analysis of the electrolyte solution in mol percent showed:

N- methoxy met hyl-N-met hy! Formamide 86%

ⁿ NN-dimethylformamide 8%

Methanol 6%

This corresponds to a current efficiency of 81.2% (based on the Ν, Ν-Dimethylformamui) and one 4, i energy expenditure of 0.68 kWh mol of product.

Example 2

In the electrolytic cell described in Comparative Example 1 a mixture of 39.9 g N.N-Di-

Filled with λ-, methylformamide and 19.2 g of methanol with the addition of 7.5 g of potassium perchlorate. The temperature is kept at 50 "C during the electrolysis. After switching on the electrolysis current, the anode current density is 5.4 A dm ² and the electrolysis

) (] Voltage 7.5 volts. Agitation is effected by a magnetic stirrer with 30 to 35 Upin. The cell st h \ under normal pressure. The escaping through the gas exit gases are passed through a RUckflußkühlei, which is cooled to -10 ° C. The case-condensing After a current equivalent of 1.202 Faraday had passed, the experiment was ended. After removal of the electrolyte salt, the analysis of the electrolyte solution in mol percent resulted in:

N-methoxymethyl-N-methylformamide 91%

Ν, Ν-dimethylformamide 5%

Methanol 4%

This corresponds to a current yield of 92.2 ° / ί (based on the N, N-dimethylformamide) and an energy consumption of 0.63 kWh / moi product.

The results of further Examples 3 to K are shown in Table I.

Table I Examples 3 bK

No ('urhiinsiiiirciimid N CH,
/ Slnikliir H 3 H-C N CH, C) CH, 4th H C - CH,
/ C) N
\ \
CH, S. CH, - C
Ii CH, Ii
O

IO

Il

CH, C-N

O H

ι N-CH,

C)

/ "■

Η — C-N

! i \

O CH,

CH,

H-C-N

O CH,

CH, H-C-N

Il ^X

O CH ₃

H — C — N

Il \

O CH ₃

37.5

41.8

37.3

alcohol
Slnikliir

37.4 CH ₁ C) H

η-C ₄ HgOH

.13.2 CH ₁ C) H

CH, OH CHjOH

37.3 CH ₁ OH

37.3 CH ₃ UH

37.3 CH ₃ OH

CH ₃ OH

16.4

30.9

16.4

13.5

16.4

16.4

16.4

16.4

9.4 KPF ,,

7.7 K PF "

14.4 8.3

K PF ₁ ,

9.8 KPF ,,

5.0 NH ₄ ClO ₄

8.3 NH ₄ PF,

5.4 NH ₄ BF ₄

8.2 ») (CHj) ₄ NBi

6.0 NH ₄ ClO ₄

H — C — N

Il \

O CH ₃

C ₂ H ₅

C ₂ H ₅ -CN

O H

26.0 UC ₄ H ₉ OH

50.6 CH ₃ OH

26.4

16.0

4.2 NH ₄ ClO ₄

5.0 NaBF ₄

continuation

Nr Carhcinsiiiirciiniid

Slrnkliir

C ₂ H,

14 CH ₁ -CN

'Il \

OC ₂ H,

cn,

15 Il C N

j \
O CH ₁

cn.,

16 HCN

I! \

O CH ₁

Table I continued

No-risk-factor

3 N- (i-methoxyethyl) formamide

4 N-n-Butoxymethyl-N-methylformamide

5 N-methoxymethyl-N-methyl-acetamide

6 N-methoxymethylacetamide

7 l-methoxymethyl-4-methyl-azetidinone-2

8 N-methoxymethyl-N-methylformamide

9 N-methoxymethyl-N-methylformamide

10 N-methoxymethyl-N-methylformamide

11 N-methoxymethyl-N-methylformamide

12 N-n-Butoxymethyl-N-methylformamide

13 N - (* - MethoxyäthyI) -propionäureamid

14 N- (x-methoxyethyl) -N-ethylacetamide

15 N- (γ-hydroxybutoxy> -methyl-N-methylformamide

N-ia-methyl-γ-hydroxy-propoxy I-methyl- N-methylformamide

16 N-methoxymethyl-N-methylformamide

Alkrl.nl

| μ | structure

40.0 CH ₁ OH

26.2 CH ₁ CH C} \ ₂ CH ₂ OH

OH

37.3 CH ₁ OH

1.019

For this purpose, 1 sheet of drawings

12.7

32.2

16.4

It- · I

6.4 K PF ₁

3.75 NH ₄ RF ₄

16.8 In-C ₄ Rj ₄ NBF ₄

Sirommci .ν
| Farada>] ■ \ ushenle Λ η fa η c> -
spaniMni! π ncri-Mc-
aiifwand
[kWh / m 1.022 52.1 9.0 1.56 0.910 79.5 15.0 1.56 0.900 84.7 10.0 0.95 1,026 68.2 10.4 1.02 0.840 78.2 8.2 1.22 1,021 86.5 6.0 0.52 1,021 95.2 6.5 0.41 1,021 68.2 19.0 1.91 1,021 91.0 5.4 0.37 0.712 82.7 10.5 1.25 1.06 49.9 16.0 3.11 0.694 75.5 10.0 1.23 0.716 79.1 10.1 1.12

88.3

8.3

Claims (1)

Claim: Process for the alkoxylation of nitrogen alkylated carboxamides of the general Formula (I) R ₁ -CN Il \ O CH ₂ -R ₃