Because this conversion utilizes a very dangerous chemical, acetic anhydride, it is necessary to construct a safety box in which to perform this operation. This places a shield between the chemist and the apparatus, and has the operation taking place in a separate atmosphere. The fumes from heated acetic anhydride are very flammable and poisonous. Inhalation of the fumes is one of the most unpleasant and dangerous experiences we have had, and that is why we feel it is necessary to present this section on building a glove box. Acetic anhydride is so difficult to handle safely that it is a necessity to use standard laboratory equipment and procedure. The reaction is monitored and controlled from outside of the box by observing the equipment through a safety-glass window and manipulating the apparatus with long gloves scaled to the shield. The box should have an adequate exhaust fan with a sparkless electric motor to quickly evacuate any fumes that occur while transferring solutions or from a spill or other mishap. A fire extinguisher should be mounted inside of the box. In case of fire or explosion, the chemist is protected- by the thick front piece of the box and by its structural design. The box can also be used for any other chemical operation requiring an artificial atmosphere to avert fire or explosion.
An artificial atmosphere is created by replacing the air in the sealed box with anhydrous nitrogen gas. This makes flame or combustion (oxidation in general) impossible. The nitrogen is introduced into the chamber through an opening in one side, near the top of the box. The displaced air is removed through a valve near the bottom of the opposite end. Success here is determined by attempting to strike a match inside of the box. When oxygen has been removed, this becomes impossible. The exhaust fan is then used only when it becomes necessary to evacuate the atmosphere in the box.
Diagrams showing details of construction follow:
The three stations are utilized as follows: The equipment and bottled chemicals are put into the right-hand side of the box by lifting the hinged side piece. The apparatus is prepared at this station and operated in the middle at station two. The bottles are opened at station one, using the gloves, from the outside of the box after the side flap is closed and the atmosphere has been replaced with anhydrous nitrogen gas. The operator need never be exposed to the dangerous chemicals except within the controlled atmosphere of the box.
The side walls of the box are made of thin plywood and hinged at the top. This serves two purposes: access to the box is available from both ends and in case of explosion (which is unlikely if the chemist is alert and following directions), the force would be expended through the side panels while the thick reinforced front boards protect the chemist.
THC is converted to THC acetate by refluxing for two hours with acetic anhydride. Collect the following apparatus to be assembled as illustrated in the diagram:
1 500 ml Pyrex round-bottom boiling flask with a ground glass fitting.
2, Tubular type condenser with ground glass male fitting that matches the fili ng on the boiling flask.
8, S i.ti pot of at least 2000 ml as hot oil bath for heating boiling flask.
C T: .niometer for monitoring the oil bath temperature.
1. SpaiiUess electric hotplate.
6 Rheostat to control temperature of hotplate from outside the box.
7 Ring stand and proper clamps for securing flask and condenser.
8. Cottonseed oil.
9. Acetic anhydride.
10. immersible water pump, bucket, and hoses for filling condenser.
The principle of the refluxing operation is approximately the same as was used for isomerizing the cannabidiol to THC with the kitchen apparatus. The explosive and noxious nature of the acetic anhydride necessi tates the use of the safety box. Although it is not necessary to use a glove box for the operations of extraction and isomerization using the kitchen method previously described, these steps may also be done in the box if it is convenient, as an added measure of safety.
The solution of acetic anhydride and cannabis oil is boiled in the round-bottom flask. The fumes rise into the icewater-cooled condenser, where they are condensed back into liquid, thus relieving the pressure created by boiling. The drops then fall back into the solution.
Before assembling the apparatus, it is necessary to take these factors into account: The temperature of the hotplate must be controlled from the outside of the box. This necessitates a variac type rheostat in the power line to the hotplate. The pail containing the immersion pump which circulates the icewater coolant through the condenser should also be outside of the box. There should be two small holes in the safety box for the icewater input and return hoses. Although the sink at the left station of the box seems handy for the coolant pump, this would necessitate opening the side panel while the refluxing is in progress to add ice and remove water.
Assemble and operate the equipment in this manner: Open the right side panel and assemble at station one the boiling flask, condenser, oil bath, and hotplate, as illustrated in diagram 00. Each item is secured to the ring stand with adequate clamps. Position the flask at least one-half inch above the bottom of the oil bath. Do not make electrical connections or secure the coolant hoses to the condenser yet, as the entire apparatus will be moved over to the center station before beginning.
The boiling flask, prior to being put in the safety box, should contain a measured amount of cannabis extract. Also place in the safety box an unopened bottle of acetic anhydride, an empty graduated beaker, a beaker containing sufficient cottonseed oil to fill the oil bath to a level slightly above that of the cannabis oil-acetic anhydride solution that will be in the flask, and an empty, open-top container of the same height as the boiling flask and of a slightly larger diameter. This container is for holding the boiling flask safely when the apparatus is dismantled. Loosen the clamps holding the condenser and slide them up the ring stand so that the mouth of the boiling flask is accessible for addition of the acetic anhydride. Close the right side panel; fill the chamber with nitrogen, then, using the gloves through the front board at station one, open the bottle of acetic anhydride. Pour an amount into the graduated beaker equal to three times the volume of the cannabis oil in the boiling flask. Replace the cap on the acetic an hydride bottle and carefully pour the acetic anhydride from the graduated beaker into the boiling flask. Securely replace the condenser on the boiling flask and loosely fit a solid rubber stopper to the top of the condenser.
Open the side panel and carefully move the apparatus to the center station. Connect the input icewater hose to the lower fitting of the condenser. The return hose should run from the uppermost fitting (assuring that the condenser is always filled with circulating water) through a hole in the safety box to a pail containing the icewater and immersion pump. Secure the fittings on the condenser with twisted wire or automobile-type hose clamps. The power wire for the hotplate is also run through a hole in the safety box and connected to the rheostat. The oil bath temperature should be monitored with a thermometer which should be adjusted for observation through the safety glass window. Add the cottonseed oil to the bath. Remove the empty beaker and the closed bottle of acetic anhydride. Close and secure the side panel. Now, bleed more nitrogen into the box until vou are fairly sure that the air has been completely replaced by nitrogen. Striking a match is not a good idea for a test at this time, but if the test is tried a few times prior to beginning the operation, you should have a good idea af how long it takes to drive out the air completely. Fill the pail containing the immersion pump with water and ice, turn on the pump, and fill the condenser with circulating ieewater. Begin heating the oil in the oil bath by turning on the electric hotplate. Slowly raise the temperature indicated on the thermometer, giving the solution in the flask time to heat to the temperature of the bath. Notice when the solution of cannabis oil and acetic anhydride begins to fume and droplets of pure acetic anhydride form in the condenser and fall back into the solution. Continue slowly-raising the temperature until the solution in the flask begins to boil. Stabilize the Sath temperature at this point. Note the time and continue to boil ior three hours. Be sure to keep ice in the container with the immersion pump. Alter three hours of refluxing, turn off the electricity to the hotplate and allow the solution to cool to room temperature. Be certain to keep ieewater circulating through the condenser. After the solution has remained at room temperature for at least two hours, check the rubber stopper at the top of the condenser. It should form a perfect seal, but not be too tightly jammed into the condenser. Next turn off the immersion pump and let the apparatus sit at room temperature for another hour. At the end of this time loosen the clamps holding the condenser and slide it up the ring stand as before, giving access to the aperture of the boiling flask. Remove the rubber stopper from the top of the condenser and fit it tightly in the top of the boiling flask. Loosen the clamp holding the boiling flask and remove the flask from the oil bath. Wipe the flask clean of oil and set it into the empty open-top container which was set in the box earlier. Open the side panels and dismantle the equipment.
Removing the acetic anhydride by distillation is the next step; see diagram 10. The distillation requires the following equipment not used for refluxing:
1. A Pyrex distillation flask of the same capacity as the boiling flask, and two Erlenmeyer flasks, also of the same capacity.
2. An assortment of glass tubing, flexible tubing, and rubber stoppers.
3. A large pan to be used as an ieewater bath for the Erlenmeyer flasks.
As the solution in the distillation flask is heated, the acetic anhydride vaporizes: the fumes rise and travel down the side arm of the distillation flask into the condenser where they are cooled to liquid. The recondensed acetic anhydride is collected in the receiving flask at the end of the condenser. This flask and a back-up flask used for safety are immersed in an ieewater bath.
Assemble the equipment at stations one and two as illustrated in diagram 10. Be certain that the condenser is at a great enough angle that no acetic anhydride can lie between the condenser bottom and the exit tube. The glass tube for the introduction of the recondensed acetic anhydride-should extend deeper into the flask than the exit tube. The same holds true for the back-up flask, even though it is unlikely that any fumes or liquid will go beyond the first flask. The tube leading from the back-up flask should be open at the end.
Close the side panel, replace the atmosphere with nitrogen gas as before, and proceed as follows: Using the gloves, pour the cannabis oil-acetic anhydride solution from ihe boiling flask into the distillation flask. Use a funnel with a tube long enough to extend past the side arm of the distillation flask. This eliminates the chance of any solution running into the condenser. Secure the rubber stopper to seal the top of the distillation flask. Add the cottonseed oil to the oil bath and the ice and water to the ice bath. Tunl on the immersion pump and the hotplate. Slowly raise the temperature indicated by the thermometer in the oil bath to that used for the refluxing. Retain this temperature until no more acetic anhydride distills. Continue this process until certain that all acetic anhydride is evaporated and collected. Note that the volume of cannabis oil acetate now in the distillation flask will be up to twenty-five per cent more than the volume of the oil prior to acetylation. Retain the oil temperature for one-hour after the last traces of acetic anhydride have been removed. Turn off the hotplate, and, with the water still circulating through the condenser, allow the oil to cool to room temperature. Drain the water from the ice bath and wipe the basin completely dry. Using the gloves at station one, remove the two-holed stopper from the Krlenmeyer flask and replace it with a solid rubber stopper. Loosen the clamp and remove the flask from the ice bath. Very thoroughly dry the outside of the flask, removing any traces of water. Carefully pour the acetic anhydride from the flask into a safety container like that used for (he sulfuric acid, a glass bottle litted into a metal can.
Remove from the safety box the flask containing the cannabis oil acetate. Slowly, one drop at a time, add several volumes of pure alcohol to dis solve the oil. Pour this solution into five volumes of water and extract with petroleum ether as was done in the purification techniques following the isomerization. Evaporate the ether in the stew pot apparatus as was done before and collect the ether. Redissolve the resultant oil in alcohol and pour once again into water. Extract again with petroleum ether, which is evaporated and collected as before. The resultant oil contains THC acetate and may be consumed in any of the customary manners.
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