Chapter 83: Synthesis experiment (below)

　　 "The toluene has turned blue."
　　 "Then toluene can be collected in the solvent distillation head."
　　 Chen Wanqing walked to the fume hood and adjusted the three-way valve of the solvent distillation head to a three-way state.
　　The condensed toluene will accumulate in the solvent distillation head instead of returning to the round bottom flask below.
After 　　 collected for about one minute, Chen Wanqing turned off the magnetic thermostat heating stirrer.
　　 "There are already about 50 milliliters of re-vaporized toluene, enough for us to use this time, we can use it after it cools." Chen Wanqing said:
　　"Next, the monomer is weighed.
　　 Before weighing, we need to calibrate the balance.
　　Because the polymerization reaction requires very strict material ratio, it must be very accurate when weighing the monomer mass. "
　　 She walked to the experiment platform and turned on a balance.
　　 During the start of the balance, she took out a standard 100 gram weight from the cabinet.
　　 Then, she peeled the balance and put the weight on.
　　 indicates that the number is 99.9815 grams.
　　 "The error is not small, I guess Duan Yun has never been calibrated when using it."
　　 After finishing speaking, Chen Wanqing took off the weight and adjusted the balance to the calibration mode.
　　 Then put a standard weight on the balance and pull up the glass door of the balance.
　　 After a few seconds, the balance prompts that the calibration is complete.
　　At the same time, the balance display shows 100.0000 grams, and the fluctuation range of the reading is only 0.0002 grams.
　　 "The indication is so stable." Xu Qiu said.
　　 "Yes, if there is no outside disturbance, the metal block is so stable." Chen Wanqing said:
　　 "Our raw materials are different. The monomer is powdery, charged, and the mass is small, the reading will be relatively floating, so be patient when weighing."
There are two balances of the same model. Xu Qiu calibrated the other balance.
　　 After calibrating the balance, the two took out the dried two-necked flask from the oven, put it in a magnetic stirrer, and plugged the two bottle mouths with rubber stoppers, and set aside.
　　 Then, each monomer was weighed, and the monomer raw materials were poured into a two-necked flask through weighing paper.
　　 Next, assemble the balloon, three-way valve, and rubber band to make a nitrogen ball.
　　The preparation work is basically completed.
　　……
　　 Chen Wanqing reached out and touched the outer wall of the solvent distillation head, and said:
　　 "The toluene has almost cooled to 50-70 degrees Celsius and is ready for use."
　　 She opened the three-way valve of the solvent distillation head to connect it to the outside world, and took the toluene solvent with a disposable PE cup.
　　 Then, use a disposable dropper to transfer the toluene in the PE cup to a two-necked flask, about 15 ml.
　　 "The next step is to build a condensing reflux device for the synthesis reaction. The principle is the same as that of re-vaporized toluene." Chen Wanqing finished speaking, and gave a look.
　　 Xu Qiu understood, nodded and said, "I will do the next steps myself."
　　 So, he turned on the fume hood next to the senior sister, and simultaneously set up the experimental device with her.
The principle of the 　　 reaction device is to evaporate toluene and then reflux. The only difference is that no solvent distillation head is needed to collect the toluene.
　　 So only two-necked flask, spherical condenser, three-way valve, nitrogen ball are installed from bottom to top, and then condensed water is connected.
After the installation of 　　 was set up, Xu Qiu glanced at the senior sister next to her, and she only completed 70% of the progress.
　　Because of the subsequent operations, he had already learned through system imaging in advance, so he simply continued the experiment.
　　 First, use a vacuum pump to vacuum and then add nitrogen as before, repeat three times.
　　 However, the volume of the closed system is relatively small this time, and a three-way valve needs to be used to carefully control the suction of the vacuum pump.
　　 There is an anti-suction device in the pipeline of the vacuum pump, so you don’t have to worry about it.
　　 But if the suction is not well controlled, the toluene solution in the bottle will be sucked away by the vacuum pump, and the experiment will fail.
　　 Xu Qiu turned on the vacuum pump and slowly turned the three-way valve.
　　 After the toluene in the bottle boils due to the decrease in air pressure, and white mist appears inside the bottle wall, immediately turn the three-way valve to make up the nitrogen.
　　 was repeated three times without any accidents.
　　 Chen Wanqing had just set up the equipment and was about to teach Xu Qiu the next operation, but found that he was already vacuuming.
　　 She hurriedly said: "Scholar, be careful to smoke, be careful to pump the toluene away."
　　 "I have drawn three times and I am ready to add catalyst." Xu Qiu said.
　　 "Well, then you wait for me a little bit."
　　 Chen Wanqing discovered that she was a little accustomed to Xu Qiu's experimental ability.
　　 Maybe he will surpass me in a while.
　　 Chen Wanqing shook her head, stopped thinking about it, and concentrated on experimenting.
　　 Carefully, she unscrewed the three-way valve a little bit and pumped for more than twenty seconds before the toluene in the two-necked flask showed signs of boiling.
　　 waited a while, white mist appeared in the bottle wall, she quickly turned the three-way valve to replenish nitrogen.
　　 was repeated three times without any accidents, but the speed was much slower.
　　 Chen Wanqing said after finishing:
　　 "Weigh the catalyst. The zero-valent palladium catalyst will quickly deactivate under oxygen and high temperature environments, so it needs to be weighed quickly and added to the reaction vessel."
　　 She picked up the reagent bottle containing the tetrakis (triphenylphosphine) palladium catalyst, cut the package, and opened the yellow packaging tape on the cap~EbookFREE.me~ glanced at the inside of the bottle and said:
　　 "Yellow powder is a normal state. If the catalyst turns black, it is probably deactivated."
　　 After weighing the catalyst with the weighing paper, she ran to the fume hood while holding the weighing paper.
　　 Xu Qiu also followed her, with the weighed catalyst, walked quickly to the fume hood.
　　 Then the two-necked flask and the spherical condenser were pulled apart, a gap was leaked, and the catalyst was poured into it. At this time, the nitrogen balloon was spraying nitrogen continuously along the lower end of the spherical condenser.
　　 After pouring all the catalyst into the reaction vessel, insert the spherical condenser tube back into the two-necked flask, connect the three-way valve to the vacuum pump, and repeat the operation of vacuuming and releasing nitrogen five times to ensure that the entire system is basically nitrogen atmosphere.
　　 After the operation, the nitrogen ball that was the size of a human head is now only the size of a solid ball.
　　 "Senior sister, I'm fine, do you want to heat up immediately?" Xu Qiu asked.
　　 "Heat up, 120 degrees Celsius, two or three hundred is enough for the speed."
　　 Xu Qiu sets the parameters, confirms that the magnetic stirrer can rotate normally, and turns on the condensate switch.
　　 waited a while, the senior sister got it right, she said:
　　 "Our synthesis reaction must be protected from light, so we must cover the aluminum foil around the reaction vessel."
　　 After covering the aluminum foil, she continued:
　　 "After the temperature reaches 120 degrees Celsius, we should also observe whether it can return normally, that is, to see if there is any toluene liquid flowing back on the spherical condenser."
　　……
　　 Ten minutes later, Chen Wanqing opened the corner of the aluminum foil of the reaction vessel and said:
　　 "We both have toluene reflux, there should be no problem, right?"
　　 "Should?"
　　 "Senior sister, I am a little panicked if you ask me like this."