Reactions proceed according to Scheme 1.
Scheme 1Reagents and Materials:
Synthesis
Scheme 1
- 10 g of pure P2P (steam distillation purified)
- 45-55 g of silica gel d=2.5-4 mm (NOT powder)
- 3 g of sodium borohydride (equivalent in moles)
- 65 ml of absolute isopropyl alcohol
- 18.1 – 20 ml of 35-40% aqueous methylamine
- 50-100 g of anhydrous sodium sulfate Na2SO4
- 200-250 ml of dichloromethane
- 50-100 g of ammonium chloride NH4Cl
- 50 ml of concentrated sulfuric acid (88%)
- 10-15 ml of diethyl ether
- 200-300 ml of distilled water
- 5-10 g of sodium hydroxide
- 500-1000 g of ice
- cool packs
- 1 L three-neck flask
- Distillation setup
- Vacuum filtration setup
- Chemical beakers
- Glass adapters
- 2 L separating funnel
- Heater
Synthesis
Stage 1
Prepare the mixture in the container one day before the synthesis by combining 20 ml of methylamine, 65 ml of absolute isopropyl alcohol, and 15 g of anhydrous sodium sulfate. Add 2-5 g of silica gel to the mixture and periodically stir the mixture with vigorous shaking. Fig 1
Prepare the mixture in the container one day before the synthesis by combining 20 ml of methylamine, 65 ml of absolute isopropyl alcohol, and 15 g of anhydrous sodium sulfate. Add 2-5 g of silica gel to the mixture and periodically stir the mixture with vigorous shaking. Fig 1
Fig 1
Add 40 g of silica gel into a three-necked flask, connect the absorbers (a calcium chloride tube with silica gel and hygroscopic cotton), and let it stand for 0.5-1 hour for drying. Fig 2
Add 40 g of silica gel into a three-necked flask, connect the absorbers (a calcium chloride tube with silica gel and hygroscopic cotton), and let it stand for 0.5-1 hour for drying. Fig 2
Fig 2
Pour the pre-prepared and dried methylamine solution in alcohol into the reactor, additionally rinsing the sodium sulfate with portions of isopropyl alcohol. In the case where P2P was not pre-dried, set up a separating funnel with a layer of silica gel and introduce P2P into the reactor in portions. After adding all of P2P, rinse the remaining residue with several portions of isopropyl alcohol. Stir the resulting reaction mass for 2 hours, during which the temperature increases from 22 to 30°C, which should be considered for larger synthesis volumes. Fig 3
Pour the pre-prepared and dried methylamine solution in alcohol into the reactor, additionally rinsing the sodium sulfate with portions of isopropyl alcohol. In the case where P2P was not pre-dried, set up a separating funnel with a layer of silica gel and introduce P2P into the reactor in portions. After adding all of P2P, rinse the remaining residue with several portions of isopropyl alcohol. Stir the resulting reaction mass for 2 hours, during which the temperature increases from 22 to 30°C, which should be considered for larger synthesis volumes. Fig 3
Fig 3
The next step is to cool the reaction mixture (RM) to 0-5°C. Fig 4
The next step is to cool the reaction mixture (RM) to 0-5°C. Fig 4
Fig 4
Sodium borohydride is added to the reaction mixture (RM) in small portions to prevent the temperature from rising above +15°C (for about 3 hours). After adding all the sodium borohydride, the RM is stirred for 1-1.5 days at a temperature not exceeding +20°C. The temperature is maintained using cold accumulators. Fig 5
Sodium borohydride is added to the reaction mixture (RM) in small portions to prevent the temperature from rising above +15°C (for about 3 hours). After adding all the sodium borohydride, the RM is stirred for 1-1.5 days at a temperature not exceeding +20°C. The temperature is maintained using cold accumulators. Fig 5
Fig 5
Reaction mass after the reaction. Fig 6
Reaction mass after the reaction. Fig 6
Fig 6
Stage 2
The reaction mass (RM) in a three-necked flask is filled with water to dissolve the precipitate, then transferred to a separating funnel, and a sodium hydroxide solution is added. The reaction mass should have an appropriate pleasant odor, sometimes with a trace of unreacted methylamine.
Water added to RM. Fig 7
Water added to RM. Fig 7
Fig 7
The silica gel is washed with additional portions of water to extract all of the RM. Then, extraction is performed by adding dichloromethane (DCM). The process is repeated by adding DCM and water for better separation. Fig 8
The silica gel is washed with additional portions of water to extract all of the RM. Then, extraction is performed by adding dichloromethane (DCM). The process is repeated by adding DCM and water for better separation. Fig 8
Fig 8
The DCM layer is drained into a 1-liter beaker, and anhydrous sodium sulfate is added. Fig 9
The DCM layer is drained into a 1-liter beaker, and anhydrous sodium sulfate is added. Fig 9
Fig 9
Dried extract of methamphetamine in DCM. Fig 10
Dried extract of methamphetamine in DCM. Fig 10
Fig 10
Stage 3
The dried extract in DCM is introduced into a 500 ml flask (the drying agent is washed with additional portions of DCM!). Fig 11
Fig 11
The distillation setup is assembled. DCM is distilled off at the temperature 90-100°C. Complete distillation of DCM is not important. Fig 12
The distillation setup is assembled. DCM is distilled off at the temperature 90-100°C. Complete distillation of DCM is not important. Fig 12
Fig 12
The oil after DCM distilled off, should have a pleasant amine-like odor, significantly different from the smell of methylamine. Fig 13
The oil after DCM distilled off, should have a pleasant amine-like odor, significantly different from the smell of methylamine. Fig 13
Fig 13
Stage 4
The oil obtained in Stage 3 is transferred to a beaker, and an additional 10-20 ml of ethanol is rinsed from the distillation flask. Fig 14
Fig 14
A hydrogen chloride generator is assembled. Fig 15
A hydrogen chloride generator is assembled. Fig 15
Fig 15
The methamphetamine free base should have an alkaline reaction until it is saturated with hydrogen chloride. Fig 16
The methamphetamine free base should have an alkaline reaction until it is saturated with hydrogen chloride. Fig 16
Fig 16
After the beginning of hydrogen chloride evolution from the tube, you can gradually immerse it in the solution to prevent it from getting sucked in! After full saturation, the solution should have a pink, raspberry, or dark red color depending on the purity of the reagents used during the synthesis. Fig 17
After the beginning of hydrogen chloride evolution from the tube, you can gradually immerse it in the solution to prevent it from getting sucked in! After full saturation, the solution should have a pink, raspberry, or dark red color depending on the purity of the reagents used during the synthesis. Fig 17
Fig 17
Next, the obtained solution is evaporated until crystallization occurs. Fig 18
Next, the obtained solution is evaporated until crystallization occurs. Fig 18
Fig 18
Fully crystallized reaction mass. Fig 19
Fully crystallized reaction mass. Fig 19
Fig 19
The crystallized methamphetamine hydrochloride is mixed with diethyl ether and thoroughly stirred into a paste-like mass. The resulting paste is transferred onto a vacuum filter. Fig 20
The crystallized methamphetamine hydrochloride is mixed with diethyl ether and thoroughly stirred into a paste-like mass. The resulting paste is transferred onto a vacuum filter. Fig 20
Fig 20
The methamphetamine hydrochloride is filtered, if necessary, washed with additional portions of ether (ethylacetate or Et2O) (in case of heavy contamination, acetone is also added). Fig 21
The methamphetamine hydrochloride is filtered, if necessary, washed with additional portions of ether (ethylacetate or Et2O) (in case of heavy contamination, acetone is also added). Fig 21
Fig 21
The obtained methamphetamine hydrochloride. Fig 22
The obtained methamphetamine hydrochloride. Fig 22
Fig 22
The product yield is 60 - 79 %
Recommendations:
The product yield is 60 - 79 %
Recommendations:
- All reagents and glassware must be dry.
- A small portion of silica gel can be added to sodium borohydride.
- The size of the silica gel is 2.5-4 mm.
- Do not use silica gel in powder form.
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