Transcription
Welcome, TDC viewers. In this video, I will be synthesizing methylamine hydrochloride. Methylamine hydrochloride is the simplest primary amine. It has a strong odor, similar to fish. It is an important starting chemical for the preparation of many other organic chemicals. In particular, methylamine hydrochloride is used for the preparation of methamphetamine hydrochloride, which I will be making in another video. So stay tuned for that.
To make methylamine hydrochloride, you only need two chemicals: 250 grams of ammonium chloride and 500 grams of formalin, which is a 35 to 40% formaldehyde solution. To start the experiment, place a one-liter, two-neck round-bottom flask on a heating mantle. Attach a cold-water condenser, then place a suitable container at the end. The orientation of the apparatus is needed for downward distillation. The pump I am using for the condenser is a cheap hardware-store diaphragm pump.
Next, get a thermometer and be sure the thermometer is fully inserted into the bottom of the flask. Okay, measure out 500 grams of formalin and 250 grams of ammonium chloride. Get the 250 grams of ammonium chloride and carefully add it into the flask. After that, carefully pour the 500 grams of formalin into the flask. After the addition of the ammonium chloride and formalin, attach the thermometer to the flask. Now turn the heat on. Heat the flask slowly until the temperature reaches 104 degrees Celsius and maintain the temperature at this point until no more distillate is collected. Note: this takes about four to five hours. Once the temperature reaches 104 degrees Celsius, we can see a clear distillate that is collecting in the beaker. The clear distillate contains methyl formate and dimethoxymethane.
Once there is no more distillate to be collected, remove the flask from the heating mantle and cool the contents of the flask rapidly to room temperature. The white precipitate forming is ammonium chloride. Get the distillate and pour it into a suitable container and store it in a dark, cool place. Note: I am not discarding the distillate as I might need the methyl formate or dimethoxymethane for a future experiment. To cool the flask more efficiently, place it in a room-temperature water bath.
After the flask has cooled down to room temperature, carry out filtration to remove the precipitated ammonium chloride crystals. After the ammonium chloride has been removed by filtration, a clear yellow liquid should be seen in the side-arm flask. Pour the filtrate into a suitable beaker and start to heat and concentrate the filtrate to one-half of the original volume. As we reach the halfway mark, we see white crystalline ammonium chloride crystallizing out. Cool the beaker to room temperature, and more ammonium chloride will precipitate out. Again, filter to remove the precipitated ammonium chloride crystals. After the filtration, again evaporate the filtrate until a crystalline scum forms on the surface of the solution. Due to me fooling around with the camera, I accidentally boiled off too much liquid, yielding a crystalline cake left in the beaker. This is not detrimental as it will only prolong the purification of methylamine hydrochloride from ammonium chloride and other impurities. Anyway, the beaker now contains crystalline methylamine hydrochloride, ammonium chloride, and dimethylamine hydrochloride.
In order to remove the dimethylamine hydrochloride, add chloroform directly into the beaker and stir. Once the chloroform is added and the mixture stirred, filter off the methylamine hydrochloride and ammonium chloride at the pump and wash it with a little amount of chloroform. You can safely filtrate consisting of dimethylamine hydrochloride if you wish. Again, concentrating the filtrate to about half the original bulk will yield dimethylamine hydrochloride crystals. As we can see on the filter, the crystals of crude methylamine hydrochloride, as well as some ammonium chloride.
In order to purify the crude methylamine hydrochloride and remove chloride, a 500 milliliter round-bottom flask was placed on a heating mantle fitted with a reflux condenser carrying a cotton wool guard tube. Add the crude methylamine hydrochloride and ammonium chloride crystalline mixture to the 500 mL round-bottom flask and add 250 mL of absolute ethanol. Heat the mixture to boiling for about half an hour and allow the undissolved material to settle. Obtain a clear solution. Cool the solution, then the methylamine hydrochloride will separate. Filter the pure methylamine hydrochloride crystals. White, flake-like crystals should be observed. Note: the filtrate can be used for another extraction. Four or five extractions are required to extract all of the methylamine hydrochloride. The yield of the recrystallized material is about 100 grams. Also note that this method of drying methylamine hydrochloride is by centrifuging; the compound is hygroscopic.
There we have it, TDC viewers. We have easily synthesized methylamine hydrochloride in high yield and purity.