JPH1087601A - Production of 3-sulfopropylbetaines - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of industrially manufacturing 3-slufopropylbetaines, safely, easily, in high yield using simple equipment by carrying out a reaction of a tertiary amine and a propane 1,3-dihalide to afford a quaternary ammonium compound then affecting a sulfite salt. SOLUTION: The 3-sulfopropylbetaines of formula III:R≡N<+> -CH2 -CH2 -CH2 - SO3 - is obtained by carrying out a reaction of the tertiary amine of formula I:RE≡N (R is a residue of a tertiary amine) and a dihalide of a linear chain alkyl of formula II: X-CH2 -CH2 -CH2 -Cl (X is Br or I), then carrying out the reaction of reaction product and an oxyacid salt of sulfur comprising sulfite salt, bisulfite or pyrosulfite salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Sulfopropyl betaines have an appropriate viscosity under an appropriate formulation, have excellent detergency at low temperatures, and have excellent storage stability even under oxidizing conditions. Cosmetics,
In the field of metal cleaning, etc., it is widely used as a component of detergents, detergents, bleaching agents, and further, an antistatic agent for plastic molding materials, a film, a coating agent such as a woven fabric,
In addition, it is also used as an emulsifier and the like.

[0002]

BACKGROUND OF THE INVENTION As described in West German Patent 2,409,412, a tertiary amine is subjected to a ring-opening reaction with propane sultone to simultaneously carry out sulfonation and quaternization of a tertiary amine. A method for producing sulfopropyl betaines is already known. However, since propane sultone is known to have a very strong carcinogenicity, the above method is unsuitable for industrial production of sulfopropylbetaines.

On the other hand, as described in Japanese Patent Application Laid-Open No. 2-160575, there has been proposed a method for producing a corresponding sulfobetaine by reacting a tertiary amine with a haloalkyl sulfonate. Actually, as the haloalkyl sulfonates, sodium 3-chloro-2-hydroxypropanesulfonate obtained by reacting epichlorohydrin with sodium hydrogen carbonate is used, and therefore, sulfo-2-hydroxypropyl is used. Only trialkylammonium betaines are being produced.

Thus, in this reaction, 3-chloro-
It is expected that 3-sulfopropylbetaines can be obtained by using sodium 3-chloropropanesulfonate instead of sodium 2-hydroxypropanesulfonate. Sodium 3-chloropropanesulfonate is described, for example, in J. Amer. Chem. Soc., 82 (1960) 1988.
As described in 1-Bromo-3-chloropropane and sodium sulfite in ethanol / water (volume ratio 3).
/ 1) can be obtained by reacting in a mixed solvent. However, according to this method, the yield is low and the separation or purification of the product is not industrially easy. The method of reacting sodium 3-chloropropanesulfonate with a tertiary amine is a method for producing 3-sulfopropylbetaines which is industrially difficult to employ, in terms of both production cost and production process. It is.

Further, Japanese Patent Application Laid-Open No. 57-53456 discloses that a trialkylallylammonium salt and a bisulfite are used in an aqueous solution or an alcohol / water mixed solution.
In a method for producing sulfobetaines by reacting in the presence of an iron (II), copper (II) or Mn (II) ion catalyst, the reaction is carried out while blowing air into the above solution to obtain a triphosphate. A method has been proposed in which a sulfite group is selectively introduced into an alkylallylammonium salt at three positions in an anti-marker manner.

However, also in this method, when the reaction is carried out in an aqueous solution, the reaction mixture becomes very high in viscosity with the progress of the reaction, so that it is difficult to handle the reaction mixture. On the other hand, isopropanol / water When the reaction is carried out in an alcohol / water mixed solution such as a mixed solution, it is necessary to continuously feed oxygen into the solution under heating and stirring. The available volume in the vessel is significantly reduced, the productivity is low and the selectivity of the reaction is low. Furthermore, this method is disadvantageous from the viewpoint of equipment for industrial production, because an additional equipment for blowing air into the reaction vessel is required, so that the equipment is bulky and expensive.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a conventional 3-
It has been made to solve the various problems as described above in the production of sulfopropyl betaines,
Without using propane sultone as a raw material, a corresponding quaternary ammonium compound is obtained by the reaction of a tertiary amine with a 1,3-dihalogenated propane, and sulfite is allowed to act on the quaternary ammonium compound. Accordingly, an object of the present invention is to provide a method for industrially and safely producing 3-sulfopropylbetaines easily and in high yield.

[0008]

According to the present invention, there is provided a tertiary amine represented by the general formula (I) R≡N (I) wherein R represents a tertiary amine residue. , general formula _{(II) X-CH 2 CH} 2 CH 2 -Cl (II) ( wherein, X represents a bromine atom or an iodine atom.) reacting a linear 1,3-dihalogenated propane represented by And then reacting the resulting reaction product with a sulfur oxyacid salt selected from sulfites, bisulfites and pyrosulfites, wherein R 一般 N ⁺ -CH ₂ CH ₂ CH ₂ -SO ₃ ^- method for producing 3-sulfopropyl betaine represented by formula (III) is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, the tertiary amine used as a starting material is represented by the general formula (I).

[0010]

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Wherein R ¹ represents an alkyl group having 6 to 28 carbon atoms, a cycloalkyl group or a cycloalkyl alkyl group having 6 to 28 carbon atoms, a benzyl group or a hydroxyalkyl group having 2 or 3 carbon atoms; ² and R ³ each independently represent an alkyl group having 1 to 3 carbon atoms or a hydroxyalkyl group having 2 or 3 carbon atoms) or a tertiary amine represented by the general formula (V)

[0012]

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Wherein R ⁴ represents hydrogen, an alkyl group having 1 or 2 carbon atoms, a hydroxyl group or a benzyl group, or a tertiary amine represented by the general formula (VI):

[0014]

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(In the formula, R ⁵ represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and Z represents an oxygen atom or a methylene group.)
Is a tertiary amine represented by

In the tertiary amine represented by the general formula (IV), examples of the alkyl group include hexyl,
Examples include heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl groups. A typical example of the cycloalkyl group is a cyclohexyl group, and a typical example of the cycloalkylalkyl group is a cyclohexylmethyl group. Carbon number 1
Examples of the alkyl groups (1) to (3) include a methyl, ethyl and propyl group. Examples of the hydroxyalkyl group include a hydroxyethyl or hydroxypropyl group.

Therefore, preferred specific examples of the tertiary amine represented by the general formula (IV) include, for example, N, N-dimethyl-N-stearylamine, N, N-dimethyl-N-
Examples thereof include n-octylamine, N, N-dimethyl-N-cyclohexylamine, triethanolamine, and tripropanolamine.

Examples of the tertiary amine represented by the general formula (V) include pyridine, 2-methylpyridine,
Examples thereof include 2-ethylpyridine, 4-methylpyridine, 4-ethylpyridine, 2,6-dimethylpyridine, 2-hydroxypyridine, 4-hydroxypyridine, 2-benzylpyridine, and 4-benzylpyridine.

Further, the third compound represented by the general formula (VI)
Examples of the secondary amine include 1-methylmorpholine, 1
-Ethylmorpholine, 1-propylmorpholine, 1-methylpiperidine, 1-ethylpiperidine, 1-propylpiperidine and the like.

According to the method of the present invention, the above general formula (I)
The tertiary amine represented by the general formula (II) is reacted with the linear 1,3-dihalogenated propane represented by the general formula (II) to give the following general formula (VII) [R≡N ⁺ -CH ₂ CH ₂ CH ₂ -Cl] X ^- (VII) represented by to yield the corresponding quaternary ammonium compound.

Here, according to the method of the present invention, the above 1, 3
1-chloro-3-iodopropane or 1-bromo-3-chloropropane is used as dihalogenated propane. As described above, in the reaction with the tertiary amine, the halogen ion X forms a counter ion to the quaternary nitrogen.

In such a reaction between a tertiary amine and a 1,3-dihalogenated propane, it is necessary to react the 1,3-dihalogenated propane in excess with respect to the tertiary amine. That is, 1,3-dihalogenated propane is
It is usually used in an amount of 1.1 to 10 parts by mol, preferably 2 to 3 parts by mol, per 1 part by mol of the tertiary amine. Thus, according to the method of the present invention, by reacting a small excess of 1,3-dihalogenated propane whose terminal halogen atoms are mutually different in reactivity with a tertiary amine, for example, The production of undesired by-products such as bis (quaternary ammonium) compounds having quaternary nitrogen bonded to both ends can be suppressed, and the desired quaternary ammonium compound can be obtained in good yield. Can obtain the desired 3-sulfopropylbetaines.

In the method of the present invention, a tertiary amine and
For the reaction with 1,3-dihalogenated propane, a reaction solvent is used as necessary. As the reaction solvent, an aliphatic alcohol, an aliphatic ketone or an aromatic hydrocarbon is preferable. Specifically, for example, methanol, ethanol, n
-Propanol, isopropanol, n-butanol,
Aliphatic alcohols such as t-butanol, n-pentanol, n-hexanol and 2-ethylhexanol, aliphatic ketones such as acetone and methyl ethyl ketone, and aromatic hydrocarbons such as toluene and xylene are used.

The reaction temperature is not particularly limited, but is usually in the range of 0 to 80 ° C, preferably 30 to 50 ° C, and the reaction time is usually within 24 hours, preferably 12 hours. It is about 18 hours.

According to the method of the present invention, a tertiary amine and 1,1
Reacting 3-dihalogenated propane, removing excess 1,3-dihalogenated propane and the reaction solvent from the obtained reaction mixture under reduced pressure, and removing the generated quaternary ammonium compound from the reaction system. Instead, the resulting concentrated residue is dissolved in a reaction solvent, and the above-mentioned sulfur oxyacid salt is added thereto together with water to cause a reaction, whereby the desired 3-sulfopropylbetaines can be obtained.

However, if necessary, tertiary amine and 1,1
Reacting with 3-dihalogenated propane, separating a quaternary ammonium compound from the resulting reaction mixture, purifying, if necessary, dissolving it in a reaction solvent,
Further, the desired 3-sulfopropylbetaines can also be obtained by adding water and the above-mentioned sulfur oxyacid salt and reacting them.

In order to remove the quaternary ammonium compound from the reaction mixture, the reaction mixture is concentrated, and the obtained concentrated residue is dissolved in an appropriate organic solvent by heating, if necessary, to form an insoluble solid (particularly, After removal of the inorganic sodium salts), if concentrated or cooled, a purified quaternary ammonium compound can be obtained. As the organic solvent, for example, a ketone such as acetone or an alcohol such as isopropanol is preferably used. If necessary, further recrystallization from such a solvent can provide a more purified product.

The reaction between the quaternary ammonium compound thus produced and the oxyacid salt of sulfur is usually carried out in a reaction solvent. The reaction solvent may be the same as in the reaction between the tertiary amine and the 1,3-dihalogenated propane, and usually an alcohol / water mixture is preferably used.

In the present invention, as the oxyacid salt of sulfur, sulfite, hydrogen sulfite or pyrosulfite is used, and particularly, sodium salt is preferably used. Less than,
These are sometimes simply called sulfites. These sulfites are used per equivalent of the quaternary ammonium compound.
Usually, it is used in the range of 1.1 to 6 equivalent parts, preferably 1.5 to 2 equivalent parts.

The reaction temperature of the quaternary ammonium compound with the sulfite is not particularly limited, but is usually
30 to 105 ° C., preferably 60 to 80 ° C.
° C, and the reaction time is usually in the range of 1 to 72 hours, preferably in the range of 6 to 12 hours.

After the reaction between the quaternary ammonium compound and the sulfite is completed, for example, the reaction mixture is washed with water to remove the inorganic salts from the aqueous layer, and to remove water from the organic layer by azeotropic distillation. The organic layer is concentrated to such an extent that the desired 3-sulfopropylbetaines are barely fluid, and then the concentrated 3-sulfopropylbetaine is added to the concentrated residue so as not to rapidly cool it. An organic solvent that dissolves propylbetaines is gradually added, and then heated and refluxed again to obtain a uniform solution. After cooling and recrystallization, a purified product of the target 3-sulfopropylbetaines is obtained. Can be obtained.

As another method, after the reaction between the quaternary ammonium compound and the sulfite is completed, for example, the reaction mixture is directly concentrated to remove the reaction solvent, and a viscous concentrated residue containing inorganic salts is obtained. In this state, an organic solvent for dissolving the target 3-sulfopropylbetaines was added,
If the 3-sulfopropylbetaines are extracted, cooled, and recrystallized, the desired purified product of the 3-sulfopropylbetaines can be obtained.

In any method, the desired 3-
Organic solvents that dissolve sulfopropylbetaines, that is,
The recrystallization solvent is not particularly limited, but usually, acetone or isopropanol is preferably used.

[0034]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

Example 1 (Production of N, N-dimethyl-N-stearyl-N- (3-sulfopropyl) ammonium betaine) In a three-necked flask equipped with a stirrer, a condenser and a thermometer, 100 g of n-butanol was added. 94.0 g (0.3 mol) of N, N-dimethyl-N-stearylamine and 94.5 g (0.6 mol) of 1-bromo-3-chloropropane were charged, and the temperature was raised to 40 to 50 ° C.
After the reaction was carried out for 24 hours while maintaining the above range, n-butanol and excess 1-bromo-3-chloropropane were distilled off under reduced pressure.

[0036] n-Butanol 10 was added to the obtained concentrated residue.
g, water 100 g and sodium pyrosulfite 45 g (0.2
25 mol) and reacted at 80-85 ° C. for 8 hours. After the reaction, n-butanol was added to the obtained reaction mixture, and after washing with water, the n-butanol layer was concentrated.
The obtained concentrate was cooled while gradually adding acetone to obtain crystals, which were dried to obtain 120.0 g of white crystals.
(95% yield).

Example 2 (Production of N, N-dimethyl-NNn-octyl-N- (3-sulfopropyl) ammonium betaine)
In a three-necked flask equipped with a condenser and a thermometer, 100 g of 2-ethylhexanol, 49.7 g (0.3 mol) of N, N-dimethyl-Nn-octylamine and 1-bromo-3
After charging 94.5 g (0.6 mol) of -chloropropane and reacting for 24 hours while maintaining the temperature in the range of 40 to 50 ° C, excess 1-bromo-3-chloropropane was distilled off under reduced pressure. Was recovered.

100 g of water and 57.5 g (0.45 mol) of sodium sulfite were added to the obtained reaction mixture, and
The reaction was performed at 5 ° C. for 8 hours. After the reaction, the obtained reaction mixture was washed with water, concentrated by distilling off 2-ethylhexanol,
The obtained concentrate was cooled while gradually adding acetone to obtain crystals, which were dried to obtain 78.3 g (yield: 93%) of white crystals.

Example 3 (N, N-dimethyl-N-cyclohexyl-N- (3-
Preparation of sulfopropyl) ammonium betaine) In a three-necked flask equipped with a stirrer, condenser and thermometer, 100 g of isopropanol, 38.6 g (0.3 mol) of N, N-dimethyl-N-cyclohexylamine and 1-chloro- 3
After charging 122.7 g (0.6 mol) of iodopropane and reacting for 24 hours while maintaining the temperature in the range of 30 to 40 ° C., isopropanol and excess 1-chloro-3-iodopropane were distilled off under reduced pressure. I left.

Acetone is added to the obtained concentrated residue, and the mixture is heated and dissolved to remove insoluble solids.
N, N-Dimethyl-N-cyclohexyl-N- (3-chloropropyl) ammonium betaine iodine was collected by filtration as white crystals. 10 g of n-butanol was obtained from the white crystals.
In 100 g of water and sodium sulfite 57.
5 g (0.45 mol) was added and reacted at 60 to 65 ° C for 12 hours. After the reaction, n-butanol was added to the reaction mixture, washed with water and separated, the n-butanol layer was concentrated, and the obtained concentrate was cooled while gradually adding acetone to obtain crystals, which were dried. To give 70.3 g of white crystals (yield 94
%).

Example 4 (Production of 1- (3-sulfopropyl) -pyridinium betaine) A three-necked flask equipped with a stirrer, a condenser and a thermometer was charged with 100 g of isopropanol and 24.0 g of pyridine.
(0.3 mol) and 1-bromo-3-chloropropane 11
After 9 g (0.75 mol) was charged and reacted for 24 hours while maintaining the temperature in the range of 40 to 50 ° C., isopropanol and excess 1-bromo-3-chloropropane were distilled off under reduced pressure.

100 g of water and 57.5 g (0.45 mol) of sodium sulfite were added to the obtained concentrated residue,
For 12 hours. After the reaction, the obtained reaction mixture was concentrated to obtain a viscous concentrated residue containing an inorganic sodium salt. Isopropanol was added to the concentrated residue, extracted under heating, and the extract was cooled to obtain crystals. The crystals were dried to obtain 48.3 g (80% yield) of white crystals.

Example 5 (Production of 4-methyl-1- (3-sulfopropyl) pyridinium betaine) In a three-necked flask equipped with a stirrer, a condenser and a thermometer, 100 g of isopropanol and 28.5 g of 4-picoline (0 0.3 mol) and 153.3 g (0.75 mol) of 1-iodo-3-chloropropane.
The reaction was performed for 24 hours while maintaining the temperature in the range of 0 to 40 ° C.
After completion of the reaction, isopropanol and excess 1-iodo-
3-Chloropropane was distilled off under reduced pressure.

100 g of water and 57.5 g (0.45 mol) of sodium sulfite were added to the obtained reaction mixture.
The reaction was carried out at 18 ° C. for 18 hours. After the reaction, the obtained reaction mixture was concentrated to obtain a viscous concentrated residue containing an inorganic sodium salt. Acetone was added to the concentrated residue, and extracted under heating.
The extract was cooled to obtain crystals, which were dried to obtain 53.2 g (yield: 82%) of white crystals.

Example 6 (Production of 4-benzyl-1- (3-sulfopropyl) pyridinium betaine) In a three-necked flask equipped with a stirrer, a condenser and a thermometer, 100 g of isopropanol and 51.0 g of 4-benzylpyridine ( 0.3 mol) and 1-bromo-
119.0 g (0.75 mol) of 3-chloropropane was charged and reacted for 24 hours while maintaining the temperature in the range of 30 to 40 ° C. After completion of the reaction, isopropanol and excess 1-bromo-3-chloropropane were distilled off under reduced pressure.

100 g of water and 57.5 g (0.45 mol) of sodium sulfite were added to the obtained reaction mixture.
The reaction was carried out at 18 ° C. for 18 hours. After the reaction, the obtained reaction mixture was concentrated to obtain a viscous concentrated residue containing an inorganic sodium salt. Isopropanol was added to the concentrated residue, and the mixture was extracted with heating. The extract was cooled to obtain crystals, which were dried to obtain 81.3 g (yield: 93%) of white crystals.

Example 7 (Production of N-ethyl-N-morpholino-N- (3-sulfopropyl) ammonium betaine) n-Butanol was placed in a three-necked flask equipped with a stirrer, a condenser and a thermometer.
0 g, 14.9 g (0.3 mol) of 1-ethylmorpholine and 94.5 g (0.6 mol) of 1-bromo-3-chloropropane
While maintaining the temperature in the range of 40 to 50 ° C.
The reaction was performed for 4 hours. After completion of the reaction, n-butanol and excess 1-bromo-3-chloropropane were distilled off under reduced pressure.

100 g of water and 57.5 g (0.45 mol) of sodium sulfite were added to the obtained reaction mixture,
The reaction was carried out at 6 ° C. for 6 hours. After the reaction, the obtained reaction mixture was concentrated to obtain a viscous concentrated residue containing an inorganic sodium salt. Isopropanol was added to the concentrated residue, and the mixture was extracted with heating. The extract was cooled to obtain crystals, which were dried to obtain 66.2 g (yield: 93%) of white crystals.

Melting point: 250 ° C. (decomposition) Elemental analysis (%): Theoretical C: 45.55; H: 8.08; N: 5.91; O: 26.98; S: 13.48 Experimental C: 45.57; H: 8.09; N: 5.94 O: 26.97; S: 13.45 Infrared absorption spectrum (cm ^-1 ): 1150 to 1250
(SO ³⁻ ) ¹³ C-nuclear magnetic resonance spectrum (chemical shift (ppm) using TMS as a standard substance):

[0050]

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Example 8 (Production of N-ethyl-N-piperidino-N- (3-sulfopropyl) ammonium betaine) n-Butanol 10 was placed in a three-necked flask equipped with a stirrer, a condenser and a thermometer.
0 g, 34.3 g (0.3 mol) of 1-ethylpiperidine and 94.5 g (0.6 mol) of 1-bromo-3-chloropropane
While maintaining the temperature in the range of 40 to 50 ° C.
The reaction was performed for 4 hours. After completion of the reaction, n-butanol and excess 1-bromo-3-chloropropane were distilled off under reduced pressure.

The obtained reaction mixture was mixed with isopropanol 1
5 g, water 100 g and sodium sulfite 59.6 g (0.4
5 mol) and reacted at 60-65 ° C. for 6 hours. After the reaction, the obtained reaction mixture was concentrated to obtain a viscous concentrated residue containing an inorganic sodium salt. Isopropanol was added to the concentrated residue, and the mixture was extracted with heating. The extract was cooled to obtain crystals, which were dried to obtain 63.4 g of white crystals (yield: 90%).

Melting point: 206.3 ° C. Elemental analysis (%): Theoretical C: 51.04; H: 9.00; N: 5.96; O: 20.41; S: 13.60 Experimental C: 51.08; H: 9.01; N: 5.98; O: 20.40; S: 13.58 Infrared absorption spectrum (cm ^-1 ): 1150 to 1200
(SO ³⁻ ) ¹³ C-nuclear magnetic resonance spectrum (chemical shift (ppm) using TMS as a standard substance):

[0054]

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[0055]

As described above, according to the method of the present invention,
Without using propane sultone as a raw material, 3-sulfopropyl betaines can be easily produced in high yield by reacting a tertiary amine with 1,3-dihalogenated propane. The method of the present invention is suitable for industrial production of 3-sulfopropylbetaines because of safety of raw materials used and simplicity of required equipment.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoshika Yamamoto 1-1-1 Shinmachi, Nishi-ku, Osaka-shi Nagase Kasei Kogyo Co., Ltd.

Claims (6)

[Claims] 1. A tertiary amine represented by the general formula (I) R≡N (I) (wherein R represents a tertiary amine residue) and X-CH _{2 of the} general formula (II) Reacting with a linear 1,3-dihalogenated propane represented by CH ₂ CH ₂ —Cl (II) (wherein X represents a bromine atom or an iodine atom), and then the obtained reaction product represented by (III) ^- sulfite, formula ^{_{R≡N + -CH 2 CH 2 CH 2}} -SO 3 , characterized in that is reacted with oxygen acid salts of sulfur selected from bisulfite and pyrosulfite A method for producing 3-sulfopropyl betaines. 2. A tertiary amine having the general formula (IV): ## STR1 ## (Wherein, R ¹ is an alkyl group having 6 to 28 carbon atoms,
A cycloalkyl group or a cycloalkylalkyl group of 28, a benzyl group or a hydroxyalkyl group having 2 or 3 carbon atoms, wherein R ² and R ³ each independently represent 1 to ³ carbon atoms;
3 represents an alkyl group or a hydroxyalkyl group having 2 or 3 carbon atoms. The method for producing 3-sulfopropylbetaines according to claim 1, which is a tertiary amine represented by the formula: 3. A tertiary amine having the general formula (V): ## STR2 ## (Wherein, R ⁴ represents hydrogen, an alkyl group having 1 or 2 carbon atoms, a hydroxyl group or a benzyl group).
The method for producing a 3-sulfopropyl betaine according to claim 1, which is a secondary amine. 4. A tertiary amine represented by the general formula (VI): (Wherein, R ⁵ represents hydrogen or an alkyl group having 1 to 3 carbon atoms, and Z represents an oxygen atom or a methylene group.) 3 -Sulfopropyl according to claim 1. Production method of betaines. 5. The method for producing 3-sulfopropylbetaines according to claim 1, wherein the 1,3-dihalogenated propane is 1-chloro-3-iodopropane or 1-bromo-3-chloropropane. 6. The method for producing 3-sulfopropylbetaines according to claim 1, wherein the oxyacid salt of sulfur is a sodium salt.