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"The toluene has turned blue."

"That could collect the toluene 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.

This way condensed toluene collects in the solvent distillation head rather than returning to the round bottom flask below.

After collecting for about a minute, Chen Wanqing turned off the magnetic constant temperature heating stirrer.

"Now there are about 50 milliliters of double-distilled toluene, which is enough for our reaction this time. It can be used after it cools down." Chen Wanqing said:

"Next, the monomers are weighed.

Before weighing, we need to calibrate the balance first.

Because the polymerization reaction has strict requirements on the material ratio, it must be very accurate when weighing the monomer mass. "

She went to the bench and turned on a balance.

While the balance was running, she pulled a standard 100-gram weight from the cabinet.

Then she tares the scale and puts on the weights.

The reading shows 99.9815 grams.

"The error is not small. I guess Duan Yun has never calibrated it when he used it."

After finishing speaking, Chen Wanqing took off the weight and adjusted the balance to the calibration mode.

Put the standard weight on the balance again, and pull the glass door of the balance.

After waiting a few seconds, the balance will indicate that the calibration is complete.

At the same time, the balance display shows 100.0000 grams, and the fluctuation range of the display is only 0.0002 grams.

"The reading is so stable." Xu Qiu said.

"That's right, if there is no external disturbance, the metal block will be so stable." Chen Wanqing said:

"Weighing our raw materials is different. The monomer is powdery, charged, and the mass is still small, so the reading will be more floating. You need to be patient when weighing."

There are two balances in total, both of the same model, and Xu Qiu calibrated the other balance.

After calibrating the balance, the two took out the two-necked flasks that had been dried from the oven, put them in a magnetic stirrer, and plugged the two bottle mouths with rubber stoppers for later use.

Subsequently, the monomers were weighed separately, and the monomer raw materials were poured into two-necked flasks through weighing paper.

Next, assemble the balloon, three-way valve, and rubber band to make a nitrogen balloon.

The preparatory 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 down to 50-70 degrees Celsius and is ready to use."

She opened the three-way valve of the solvent distillation head to connect it with the outside world, and used a disposable PE cup to receive the toluene solvent.

Then, transfer the toluene in the PE cup to a two-neck flask with a disposable dropper, about 15 ml.

"The next step is to build a condensing reflux device for the synthesis reaction. The principle is the same as redistilling toluene." After Chen Wanqing finished speaking, she gave her a look.

Xu Qiu understood, nodded and said, "I'll do the next steps myself."

So, he opened the fume hood next to the senior sister, and set up the experimental device with her simultaneously.

The principle of the reaction device is to let the toluene evaporate and then reflux. The only difference is that there is no need for a solvent distillation head to collect the toluene.

So you only need to install the two-necked flask, spherical condenser, three-way valve, and nitrogen balloon from bottom to top, and then connect the condensed water.

After the device was set up, Xu Qiu glanced at the senior sister next to her. She had only completed 70% of the progress.

Because he had already learned the following operations through the system video in advance, so he simply continued the experiment.

First, as before, use a vacuum pump to evacuate and then replenish nitrogen, repeating three times.

However, the space volume of the closed system is relatively small this time, and the suction of the vacuum pump needs to be carefully controlled with a three-way valve.

There is an anti-suckback device in the pipeline of the vacuum pump, so there is no need to worry about the situation of sucking back.

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 in that case.

Xu Qiu turned on the vacuum pump and slowly turned the three-way valve.

After the toluene in the bottle boils due to the drop in air pressure and white mist appears inside the bottle wall, immediately turn the three-way valve to make up nitrogen.

Repeated three times with no surprises.

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: "Student, be careful pumping, be careful to pump the toluene away."

"I've smoked it three times, and I'm going to add a catalyst," Xu Qiu said.

"Okay, then wait for me for a while."

Chen Wanqing found that she was getting used to Xu Qiu's experimental ability.

Perhaps after a while, he will completely surpass me.

Chen Wanqing shook her head, stopped thinking about it, and concentrated on the experiment.

Carefully, she unscrewed the three-way valve little by little, and pumped for more than 20 seconds before the toluene in the two-necked flask showed signs of boiling.

After waiting for a while, white mist appeared in the bottle wall, and she quickly turned the three-way valve to replenish nitrogen.

Repeated three times, there was no accident, but the speed slowed down a lot.

After Chen Wanqing finished, she said:

"Let's weigh the catalyst. The zero-valent palladium catalyst will quickly deactivate in 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 open the package, opened the yellow sealing tape on the bottle cap, glanced at the inside of the bottle, and said:

"Yellow powder is a normal state. If the catalyst turns black, it is likely to be deactivated."

After weighing the catalyst with weighing paper, she trotted all the way to the fume hood holding the weighing paper.

Xu Qiu also followed her example and walked quickly to the fume hood with a weighed catalyst.

Then the two-necked flask and the spherical condensing tube were pulled out, a gap was leaked, and the catalyst was poured in. At this time, the nitrogen balloon was also constantly spraying nitrogen along the lower end of the spherical condensing tube.

After pouring all the catalyst into the reaction container, reinsert 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 a nitrogen atmosphere.

After the operation, the nitrogen balloon that was originally the size of a human head is now only the size of a solid ball.

"Sister, I'm fine, do you want to warm up immediately?" Xu Qiu asked.

"Let's heat up, 120 degrees Celsius, two to three hundred speeds are enough."

Xu Qiu set the parameters, confirmed that the magnetic stirrer could rotate normally, and turned on the condensate switch.

After waiting for a while, the senior sister also finished it, and she said:

"Our synthesis is done in the dark, so cover the reaction vessel with aluminum foil."

With the foil covered, she continued:

"After the temperature reaches 120 degrees Celsius, we need to observe whether it can return normally, that is, to see whether the toluene liquid flows back from the spherical condenser tube."

...

Ten minutes later, Chen Wanqing lifted a corner of the aluminum foil of the reaction container and said:

"We both have toluene reflux, so there should be no problem?"

"should?"

"Sister, I'm a little flustered when you ask me like this."

Thank you Liu Qigongzi V for the 100 point reward.