I Have a Research Support System

Chen Wanqing started experimenting with Xu Qiu and Han Jiaying standing on the left and right sides like two guards.

In the fume hood, there is a solvent reevaporation device on the left side. Now that the reevaporation has been completed, a lot of solvent remains in the distillation head.

This is tetrahydrofuran THF, the solvent to be used for the reaction later. The senior sister took the initiative to explain:

N-butyllithium is a very strong base, and many solvents with hydrogen atoms can react with it, such as water, ethanol, methylene chloride, etc., and a lot of heat will be released during the reaction, which is why it Causes of spontaneous combustion in moist air.

Under normal temperature and low temperature conditions, THF will not react with n-butyllithium, so it is selected as the reaction solvent.

There is an iron stand in the center of the fume hood. On the iron stand is a Dewar bottle. Next to it is a 500ml bottle of Sinopharm anhydrous ethanol reagent bottle and an 8-pound bottle of liquid nitrogen.

Liquid nitrogen and absolute ethanol, after being mixed in a Dewar bottle, can maintain a temperature of around minus 78 degrees Celsius.

While introducing, Chen Wanqing poured absolute ethanol into the Dewar bottle, the volume of which was roughly less than half of the hemispherical liner.

‘Ethanol, that is, alcohol, is a colorless and transparent liquid. Its freezing point is more than minus 110 degrees Celsius. Even if it falls below this temperature, it will freeze like water. '

‘The temperature of liquid nitrogen is about minus 200 degrees Celsius, so how to use liquid nitrogen and absolute ethanol to control the temperature at about minus 78 degrees Celsius? '

Xu Qiu was puzzled, because his synthesis did not involve low-temperature reactions, so he did not do related research before.

Both he and the junior sister watched the senior sister operate curiously.

I'm going to pour liquid nitrogen. Chen Wanqing was concentrating on the experiment at this time, and did not look at the two people around her.

She took off the cork of the 8-pound bottle and put it aside. White mist escaped from the bottle, because the liquid nitrogen bottle had been in the laboratory for a while, and part of the liquid nitrogen had evaporated, so it doesn't look like it now. Not very full.

The senior sister directly tilted the bottle body and poured liquid nitrogen into the Dewar bottle.

A bit like pouring boiling water, the liquid nitrogen hit the surface of the ethanol liquid, making a beeping sound, and some tiny droplets splashed out, and then disappeared in mid-air.

Then it's stirring. The senior sister put down the 8-pound bottle, capped the bottle, took a glass rod, and stirred the mixture of ethanol and liquid nitrogen in the Dewar bottle.

Xu Qiu stared at the Dewar bottle for a while, the ethanol inside was still a colorless and transparent liquid, and he didn't make a sound to disturb the senior, but thought to himself: 'It seems that there is no change. '

I need to add some more liquid nitrogen. Chen Wanqing explained to himself, then added some liquid nitrogen to the Dewar bottle, and continued to stir with the glass rod.

After that, adding liquid nitrogen and stirring repeatedly lasted for more than a minute, and the ethanol in the Dewar bottle finally changed.

You're done, it's in this viscous state. Chen Wanqing turned her head and said, Would you like to try it?

I'll do it. Xu Qiu directly took the glass rod. He had been on the sidelines just now, and felt that the liquid nitrogen cryogenic experiment was not as dangerous as imagined.

Xu Qiu tried to stir it with a glass rod, like stirring glue. ‘Perhaps a borderline state between solid and liquid? '

Han Jiaying also experimented with it and exclaimed, It's amazing.

Chen Wanqing smiled: In this state, it can be considered that the temperature is around minus 78 degrees Celsius. After that, we only need to keep replenishing liquid nitrogen to maintain the temperature.

...

With the help of Xu Qiu and Han Jiaying, Chen Wanqing built a complete reaction device.

There are Dewar bottles on the iron stand.

On the top of the Dewar bottle is an iron clip, which holds a reaction bottle.

The THF solution of the starting material of unit D and a magnetic stirring bar are contained in the reaction bottle.

A nitrogen balloon is inserted on it, and it has been pumped and discharged three times, and the entire reaction system is under nitrogen protection.

The last step, n-butyllithium. Chen Wanqing went to the refrigerator and took out the reagent bottle containing n-butyllithium tetrahydrofuran solution.

When she returned to the fume hood, she suddenly saw the hands of Xu Qiu and Han Jiaying, one holding a fire blanket and the other holding a nitrogen balloon.

What are you doing... Do you want to do this? It's scary.

Lab Safety...

Let us guard!

The two of you, husband and wife, are just n-butyllithium, not tert-butyllithium. Chen Wan gave them an innocent look and continued to operate.

In theory, dangerous reagents like n-butyllithium should be used in a nitrogen glove box, but Zhang Jiang's laboratory does not have this condition, so it can only be used by force.

She took a newly opened syringe and a needle tied with a nitrogen balloon, and inserted the needle of the syringe and the needle of the nitrogen balloon into the rubber stopper of the reagent bottle containing n-butyllithium solution.

Then, pull the plunger of the syringe to absorb the n-butyllithium solution. After a sufficient amount, lift the needle out of the liquid surface, inhale nitrogen for a while, then slowly push it out, inhale again, and push it out to ensure that the liquid in the needle mouth is drained.

Next, take out the syringe needle, keep the needle down and the syringe up, the needle and the upper part of the syringe are filled with nitrogen gas, move to the rubber stopper at the mouth of the reaction bottle, and inject the n-butyllithium solution into the reaction bottle.

Finally, unplug the nitrogen balloon needle on the n-butyllithium reagent bottle, seal the rubber stopper of the reagent bottle with adhesive tape, and put it back into the refrigerator.

Completed! Chen Wanqing let out a long breath.

Congratulations, senior. Xu Qiu and Han Jiaying congratulated each other.

Chen Wanqing's entire operation process was smooth and smooth.

Sure enough, he never had to worry about his senior sister running into danger when doing experiments, Xu Qiu murmured to himself:

The senior sister handled it very delicately. She used two needles to suck up the n-butyllithium solution to ensure that the n-butyllithium would not come into direct contact with the air.

Otherwise, if the solution is sucked directly, even if spontaneous combustion does not occur, it is possible for the needle tip to spark.

If she can maintain this state when she is doing experiments, it is estimated that her scientific research achievements will be much stronger than now.

Could it be that senior sister is destined to do some high-risk experiments?

...

After the onlookers cast their responses, Xu Qiu and Han Jiaying also started to work on their business, purifying today's four reaction products.

How do we divide the work? The junior girl ran to the liquid chromatograph and turned on the machine.

I've been to the pillars first, you can spin and steam, and then rotate. Xu Qiu thought for a while.

Yeah. Han Jiaying nodded.

This time I used a disposable blank silica gel column, with fewer samples, and the size of the column was much smaller than last time.

Because he knew in advance that this separation would be difficult, Xu Qiu put up his best efforts, which was why he chose to take the lead.

However, being cautious, he is still very confident in his experimental ability, so he did not adjust the flow rate of the solution, which is still 30 mg per milliliter.

Xu Qiu controlled the computer program and slowly increased the B component content in the A/B solvent, while keeping an eye on the state of the blank silica gel column next to it.

When the B% reached 26%, a touch of red appeared on the upper end of the blank silica gel column, and he hurriedly fixed the B component content at the ratio a minute ago, which was 24%.

That touch of red slowly moved down, but it was not as exaggerated as yesterday, forming a red band, this time there was only a small group.

After a while, the red group moved to the bottom of the silica gel column, and the ultraviolet detector produced a sample signal at the same time, and Xu Qiu immediately switched the mode to the working mode.

The needle above began to continuously spray a stream of light red liquid, and soon the first test tube was filled.

Point board, climb board, test.

There is only one sample spot, which is one of the darker product spots in the previous plate results.

Seeing this result, Xu Qiu breathed a sigh of relief.

Continue to collect, spot a plate every 3 test tubes, the results are consistent with the results of the first spot plate.

Of course, this consistency refers to the same height of the climbing board.

In fact, the concentration of the solution in each test tube is different, and the spots on the plate are also different in depth. Usually, the concentration of the solution will rise first and then decrease, so the sample spots will be dark first and then shallow when spotting the plate.

The collection of products this time is not as time-consuming and laborious as yesterday, because the flow rate is small, and there is no need to use PE cups to pick it up directly.

After all, there are only 0.5 grams of raw materials, which is one-tenth of yesterday's.

The first wave of products ended quickly, and only more than 20 test tubes were used.

After the end, Xu Qiu gave the collected solution to the junior girl to spin steam.

Then switch the mode to waste liquid mode, continue to slowly increase the volume fraction of B solvent, and increase the polarity of the mobile phase.

The second wave of samples is the shallower raw material point.

In fact, it’s okay not to collect it, but it must be cleaned, otherwise it will contaminate the next third product.

Soon the second wave of samples was collected, and he continued to increase the polarity of the solvent to collect the third wave of samples.

In the end, the third wave of samples also collected the solutions of more than 20 test tubes and handed them over to the school girls for rotary evaporation.

And the second wave of samples in the middle, that is, the raw material only collected the solution of 5 test tubes.

After thinking about it for a while, Xu Qiu directly treated them as waste liquid. If it is recycled, the maximum 50 mg of raw materials does not make much sense.

After separation and purification, he flushed the column with pure dichloromethane, emptied it for a while, and then replaced the sample column for the second sample.

This time I have experience, so I am not as cautious as last time, and the rate of increasing B% has increased a bit.

It went very smoothly and there were no issues.

After passing through the two pillars, Xu Qiu also understood the difficulty of purification, Sister, will you come instead?

Okay, Han Jiaying said confidently, Brother, just wait and see me show my power.

Come on, Xu Qiu said with a smile without saying a word, Today's progress is so fast, and we have already passed three pillars.

Yeah, I'm sure I can get two more before I leave at night. If I do the math, I can pass five a day, Han Jiaying said suddenly:

It's just a little tired, blah blah.

Then let's take a day off tomorrow.

Okay~

Thanks to nvlz for rewarding 5000 starting coins.