CN106995370A - Preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science - Google Patents

Abstract

The invention discloses a preparation method of fluoroacetic acid for forensic science qualitative and quantitative, which comprises the following steps: preparing crude sodium fluoroacetate; (II) preparing the fluoroacetic acid. The preparation method of the fluoroacetic acid for qualitative and quantitative forensic science has high yield, and the prepared fluoroacetic acid has high purity, can be directly used as a standard substance or a reference substance, and meets the requirement of forensic science poison analysis in reality.

Description

Preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science

technical field

The invention relates to the field of forensic toxicology analysis. More specifically, it relates to a method for preparing fluoroacetic acid used in the field of forensic toxicology analysis.

Background technique

Due to the great toxicity of fluoroacetic acid, it was banned by the relevant departments in 2003; however, due to its obvious effect in killing rodents in agricultural production, it is still sold in the market, especially on the stalls in the rural market, resulting in homicides and suicides Cases remain. In order to accurately identify whether the poison exists in the body, it is necessary to use standard or reference substances for qualitative and quantitative detection; however, the standard substances of the above two substances cannot be purchased from the market. For inspection and identification, it is urgent to synthesize and prepare sodium fluoroacetate and fluoroacetic acid used in the field of forensic toxicology analysis in the laboratory.

Contents of the invention

An object of the present invention is to provide a preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science, which is prepared under laboratory conditions, so that the prepared fluoroacetic acid can be directly used as a standard or reference product, meeting the reality of forensic science toxicology analysis needs.

In order to achieve the above object, the present invention adopts the following technical scheme: the preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science, comprising the following steps: (I) preparing crude sodium fluoroacetate; (II) preparing fluoroacetic acid.

The above-mentioned preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science, step (I) comprises the following steps: (1-1) dissolving ethyl fluoroacetate or methyl fluoroacetate to make solute ethyl fluoroacetate or methyl fluoroacetate ethyl fluoroacetate solution or methyl fluoroacetate solution; (1-2) add alkali to ethyl fluoroacetate solution or methyl fluoroacetate solution, and stir; (1-3) filter, and the filter residue is crude sodium fluoroacetate .

The above method for preparing fluoroacetic acid for qualitative and quantitative use in forensic science, in step (1-1): dissolving ethyl fluoroacetate or methyl fluoroacetate in alcohol, the volume ratio of solute to solvent is (2-3): 40 .

In the above method for preparing fluoroacetic acid for qualitative and quantitative use in forensic science, in step (1-1): the alcohol is any one or more of methanol, ethanol, isopropanol and n-butanol.

The above method for the preparation of fluoroacetic acid for qualitative and quantitative use in forensic science, in step (1-2): adding alkali to ethyl fluoroacetate solution or methyl fluoroacetate solution, the amount of alkali added is ethyl fluoroacetate or methyl fluoroacetate 1.05-1.5 times the amount of ester substance.

The above-mentioned method for the preparation of fluoroacetic acid for qualitative and quantitative use in forensic science, in step (1-2): the base is sodium hydroxide or potassium hydroxide, stirred for 10-20 hours, a white precipitate is generated, and the solvent is removed by distillation under reduced pressure to dryness, Obtain crude sodium fluoroacetate; in step (1-3), the obtained crude sodium fluoroacetate solid is washed with methyl tert-butyl ether, organic impurities and unreacted raw materials are removed, and dried.

The above-mentioned preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science, step (II) comprises the following steps: (2-1) dissolving crude sodium fluoroacetate in acid solution; (2-2) extracting with organic solvent; (2-3 ) to remove magnesium sulfate by filtration, and distill the filtrate to obtain fluoroacetic acid.

The above-mentioned preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science, in step (2-1): the acid solution is hydrochloric acid or sulfuric acid, and is saturated with corresponding sodium salt or potassium salt; in step (2-2), the organic solvent is diethyl ether Or methyl tert-butyl ether, the organic layer was separated after extraction, and anhydrous magnesium sulfate was added to the organic layer to dry it overnight.

The above-mentioned preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science comprises the following steps: (1) preparing crude sodium fluoroacetate;

(1-1) Dissolve 141 mmol, 13.6 mL of ethyl fluoroacetate or methyl fluoroacetate in 240 mL of ethanol;

(1-2) Add 155mmol and 6.2g of NaOH, and stir at 50°C for 12 hours to form a white precipitate;

(1-3) The solvent was distilled off under reduced pressure to dryness to obtain crude sodium fluoroacetate solid, and the obtained crude sodium fluoroacetate solid was washed three times with 30 mL of methyl tert-butyl ether to remove organic impurities and unreacted raw materials, and dried;

(II) preparing fluoroacetic acid;

(2-1) adding crude sodium fluoroacetate to hydrochloric acid with an HCl concentration of 3 mol/L, adjusting the pH value of the solution to 4, and adding NaCl to saturation;

(2-2) Extract 4 times with 100mL methyl tert-butyl ether respectively, combine the organic phases, and dry the organic layer with anhydrous MgSO ₄ overnight;

(2-3) After filtration, the filtrate was distilled to obtain 137 mmol and 10.7 g of fluoroacetic acid.

The beneficial effects of the present invention are as follows:

1. The preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science of the present invention can be prepared under laboratory conditions, the yield is high, and the prepared fluoroacetic acid has high purity, which can be directly used as a standard product (purity above 99.5%) or a reference product , to meet the needs of forensic science toxicology analysis in reality.

2. A single alcohol is used as a solvent in the hydrolysis reaction, which is convenient for subsequent recycling.

3. The amount of alkali added is moderate, so as not to take too much excess into sodium fluoroacetate, and to neutralize the acid that consumes too much later.

4. Selecting 50°C as the reaction temperature for reacting with alkali to form sodium fluoroacetate can effectively shorten the reaction time.

5. The obtained crude sodium fluoroacetate is washed with an organic solvent to remove unreacted raw materials and other organic impurities to ensure the purity of the final sodium fluoroacetate, while the unreacted raw materials can also be recovered and recycled.

6. Adjust the pH to 4 with hydrochloric acid, which is convenient to control the amount of hydrochloric acid, and also ensures that fluoroacetic acid is completely precipitated as much as possible, while improving purity and yield.

7. Choose methyl tert-butyl ether as the extraction solvent, make full use of the advantages of high boiling point of methyl tert-butyl ether, and it is easier to operate in industry and has good safety.

detailed description

Example 1

A method for preparing fluoroacetic acid for qualitative and quantitative use in forensic science, comprising the steps of: (1) preparing crude sodium fluoroacetate;

(1-1) Dissolve 141 mmol, 13.6 mL of ethyl fluoroacetate or methyl fluoroacetate in 240 mL of ethanol;

(1-2) Add 155mmol and 6.2g of NaOH, and stir at 50°C for 12 hours to form a white precipitate;

(1-3) Remove the solvent under reduced pressure to dryness to obtain crude sodium fluoroacetate solid, wash the obtained crude sodium fluoroacetate solid with 30 mL of methyl tert-butyl ether three times, remove organic impurities and unreacted raw materials, and dry;

(II) preparing fluoroacetic acid;

(2-1) adding crude sodium fluoroacetate to hydrochloric acid with an HCl concentration of 3 mol/L, adjusting the pH value of the solution to 4, and adding NaCl to saturation;

(2-2) were extracted ₄ times with 100mL methyl tert-butyl ether respectively, and the organic layer was dried overnight with anhydrous MgSO ;

(2-3) After filtration, the filtrate was distilled to obtain 137 mmol and 10.7 g of fluoroacetic acid, with a yield of 97% and a purity of 99.6%.

Example 2

A method for preparing fluoroacetic acid for qualitative and quantitative use in forensic science, comprising the following steps:

(1) preparing crude sodium fluoroacetate;

(1-1) Dissolve 13.6mL (141mmol) of ethyl fluoroacetate or methyl fluoroacetate in 200mL of methanol;

(1-2) Add 6.72g (168mmol) of NaOH, stir at room temperature for 20 hours, and slowly form a white precipitate;

(1-3) Then the solvent was removed under reduced pressure to dryness to obtain crude sodium fluoroacetate, and the obtained crude sodium fluoroacetate solid was washed three times with 30 mL of methyl tert-butyl ether to remove organic impurities and unreacted raw materials, and dried.

(II) preparing fluoroacetic acid;

(2-1) Dissolving the crude sodium fluoroacetate in hydrochloric acid with an HCl concentration of 3mol/L, and adding NaCl to saturation;

(2-2) Then extract 4 times with 100mL methyl tert-butyl ether respectively, combine the organic layers, and dry the organic layers with anhydrous MgSO4 overnight;

(2-3) After filtration, the filtrate was distilled to obtain 10.4 g (133 mmol) of fluoroacetic acid with a yield of 95% and a purity of 99.0%.

Example 3

A method for preparing fluoroacetic acid for qualitative and quantitative use in forensic science, comprising the following steps:

(1) preparing crude sodium fluoroacetate;

(1-1) Dissolve 13.6 mL (141 mmol) of ethyl fluoroacetate or methyl fluoroacetate in 200 mL of a mixed solution of isopropanol and n-butanol, the volume ratio of isopropanol and n-butanol is 1:1;

(1-2) Add 6.72g (168mmol) of NaOH, stir at room temperature for 20 hours, and slowly form a white precipitate;

(1-3) Then the solvent was removed under reduced pressure to dryness to obtain crude sodium fluoroacetate, and the obtained crude sodium fluoroacetate solid was washed three times with 30 mL of methyl tert-butyl ether to remove organic impurities and unreacted raw materials, and dried.

(II) preparing fluoroacetic acid;

(2-1) Dissolving the crude sodium fluoroacetate in hydrochloric acid with an HCl concentration of 3mol/L, and adding NaCl to saturation;

(2-2) Then extract 4 times with 100mL methyl tert-butyl ether respectively, combine the organic layers, and dry the organic layers with anhydrous MgSO4 overnight;

(2-3) After filtration, the filtrate was distilled to obtain 10.5 g (135 mmol) of fluoroacetic acid with a yield of 96% and a purity of 99.0%.

Example 4

A method for preparing fluoroacetic acid for qualitative and quantitative use in forensic science, comprising the following steps:

(1) preparing crude sodium fluoroacetate;

(1-1) Dissolve 13.6mL (141mmol) of ethyl fluoroacetate or methyl fluoroacetate in a mixed solution of 200mL of methanol and ethanol, the volume ratio of methanol and ethanol is 1:1;

(1-2) Add 6.72g (168mmol) of NaOH, stir at room temperature for 20 hours, and slowly form a white precipitate;

(1-3) Then the solvent was removed under reduced pressure to dryness to obtain crude sodium fluoroacetate, and the obtained crude sodium fluoroacetate solid was washed three times with 30 mL of methyl tert-butyl ether to remove organic impurities and unreacted raw materials, and dried.

(II) preparing fluoroacetic acid;

(2-1) Dissolving the crude sodium fluoroacetate in hydrochloric acid with an HCl concentration of 3mol/L, and adding NaCl to saturation;

(2-2) Then extract 4 times with 100mL methyl tert-butyl ether respectively, combine the organic layers, and dry the organic layers with anhydrous MgSO4 overnight;

(2-3) After filtration, the filtrate was distilled to obtain 10.5 g (134 mmol) of fluoroacetic acid with a yield of 95% and a purity of 99.0%.

Apparently, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those of ordinary skill in the art can also make It is impossible to exhaustively list all the implementation modes here, and any obvious changes or changes derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims (9)

1. A method for preparing fluoroacetic acid for qualitative and quantitative use in forensic science, characterized in that it comprises the following steps: (I) preparing crude sodium fluoroacetate; (II) preparing fluoroacetic acid. 2. the preparation method of fluoroacetic acid for qualitative and quantitative forensic science according to claim 1, is characterized in that, step (I) comprises the following steps: (1-1) dissolving ethyl fluoroacetate or methyl fluoroacetate, preparing The solute is ethyl fluoroacetate or ethyl fluoroacetate or methyl fluoroacetate solution; (1-2) adding alkali to the ethyl fluoroacetate solution or methyl fluoroacetate solution, stirring; (1 -3) Filtration, the filter residue is crude sodium fluoroacetate. 3. the preparation method of fluoroacetic acid for qualitative and quantitative forensic science according to claim 2, is characterized in that, in step (1-1): ethyl fluoroacetate or methyl fluoroacetate are dissolved in alcohol, solute and The volume ratio of the solvent is (2-3):40. 4. the preparation method of fluoroacetic acid for qualitative and quantitative forensic science according to claim 3 is characterized in that, in step (1-1): alcohol is any one in methanol, ethanol, isopropanol and n-butanol or more. 5. the preparation method of fluoroacetic acid for qualitative and quantitative forensic science according to claim 4, is characterized in that, in step (1-2): in ethyl fluoroacetate solution or methyl fluoroacetate solution, add alkali, alkali The amount of addition is 1.05-1.5 times of the amount of ethyl fluoroacetate or methyl fluoroacetate. 6. The preparation method of fluoroacetic acid for qualitative and quantitative forensic science according to claim 5 is characterized in that, in step (1-2): the alkali is sodium hydroxide or potassium hydroxide, stirred for 10-20 hours to generate The white precipitate was distilled under reduced pressure to remove the solvent to dryness to obtain crude sodium fluoroacetate; in step (1-3), the obtained crude sodium fluoroacetate solid was washed with methyl tert-butyl ether to remove organic impurities and unreacted Raw, dry. 7. according to the preparation method of the qualitative and quantitative forensic science of claim 1-6 arbitrary described fluoroacetic acid, it is characterized in that, step (II) comprises the following steps: (2-1) crude sodium fluoroacetate is dissolved in acid solution (2-2) extract with an organic solvent; (2-3) remove magnesium sulfate by filtration, and distill the filtrate to obtain fluoroacetic acid. 8. The preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science according to claim 7, characterized in that, in step (2-1): the acid solution is hydrochloric acid or sulfuric acid, and is saturated with the corresponding sodium salt or potassium salt; In step (2-2), the organic solvent is diethyl ether or methyl tert-butyl ether. After extraction, the organic layer is separated, and anhydrous magnesium sulfate is added to the organic layer to dry it overnight. 9. The preparation method of fluoroacetic acid for qualitative and quantitative use in forensic science according to claim 1, characterized in that it comprises the following steps: (1) preparing crude sodium fluoroacetate; (1-1) Dissolve 141 mmol, 13.6 mL of ethyl fluoroacetate or methyl fluoroacetate in 240 mL of ethanol; (1-2) Add 155mmol and 6.2g of NaOH, and stir at 50°C for 12 hours to form a white precipitate; (1-3) The solvent was distilled off under reduced pressure to dryness to obtain crude sodium fluoroacetate solid, and the obtained crude sodium fluoroacetate solid was washed three times with 30 mL of methyl tert-butyl ether to remove organic impurities and unreacted raw materials, and dried; (II) preparing fluoroacetic acid; (2-1) adding crude sodium fluoroacetate to hydrochloric acid with an HCl concentration of 3 mol/L, adjusting the pH value of the solution to 4, and adding NaCl to saturation; (2-2) Extract 4 times with 100mL methyl tert-butyl ether respectively, combine the organic phases, and dry the organic layer with anhydrous MgSO ₄ overnight; (2-3) After filtration, the filtrate was distilled to obtain 137 mmol and 10.7 g of fluoroacetic acid.