Lan Jie finished the trumpet, Li Zihan just finished the tuba and came out of the pit, the two washed their hands in front of the pool, Lan Jie asked: "Zihan, you stay in the classroom every day after school to study, so you didn't sign up for any extracurricular cram classes from Monday to Friday?

"Lan Jie, why do you always like to mess with my privacy?

"Just ask, do you care about you, Zihan, why is your psychological defense so high?"

"I don't have time to defend you all day long, Langer, don't think too highly of yourself. ”

"According to my observation, Zihan, you eat three meals a day in the school cafeteria, and you almost never eat outside the school, is your salary very low? By the way, I don't know where your family lives...... Okay, okay, don't mess with your privacy, let's go to eat outside the school for lunch today, I'll please. ”

"No, I just like to eat in the school cafeteria. ”

The class bell rang, and Lan Jie and Li Zihan returned to the second and third class classrooms.

"Class!"

"Stand up!"

"Hello students!"

"Hello Mr. Liu!"

"Industrious, humble!"

"Be brave and forge ahead!"

"Good, sit down. ”

Mr. Liu Hualong first talked about his teaching plan: "I will finish the chemistry elective course this semester, and after the next semester starts, interested students can sign up for the chemistry competition." In addition to the international class and the liberal arts class, about 10% of the students in our science class in Yangzhong get guaranteed offers from top universities through the four major competitions every year, so why not buy an insurance before the college entrance examination?"

"Of course, it is still the college entrance examination that determines the fate of 90% of students, and the chemistry class I am teaching now may be a bit difficult, which goes beyond the college entrance examination syllabus to a certain extent. But from another dimension, I strictly require you with the admission standards of Shuimu, Yan University, and China University of Science and Technology junior classes, even if you can't be admitted to Shuimu, Yan University, and China University of Science and Technology, you can easily be admitted to various Jiaotong University, Science and Technology University, and Industrial University, and you understand the truth?"

"Understood!"

"Good, sermon first. I will only talk about one question in this class, and if I understand this question, my classmates will be able to understand it. ”

Liu Hualong pulled out an ancestral chemistry question.

Tandem reactions, also known as domino reactions, are multi-step synthesis reactions that are completed in one synthesis operation without additional reagents or changes in reaction conditions, without the need for separation of intermediates, and subsequently converted into lower energy species. Compound I is a component of many drugs and a biologically active natural product, with hypoglycemic, anti-cancer, antiviral, anti-tumor, antimalarial, inhibition of HIV-1 activity and other functions, its preparation method is as follows:

D→F→G→H（C22H17NO）→I（C28H21NO）

In this tandem reaction, the raw material D is known, D is o-trimethylsilylphenol trifluoromethanesulfonate, and the structure brief formula has been given.

The molecular formulas of the final product I and the intermediate product H have also been given, but it is not clear what the structural formulas of I and H are due to the presence of isomers.

During the reaction from D to I, some compounds are added to facilitate the tandem reaction, including KF, 18-crown-6, CH3CN, organic E, and so on.

If E is replaced with isonitrile J, the product K is obtained. The simple formulas of the structures of the organic compounds E and J have been given, and the molecular formula of K is C18H18NO.

To sum up, students are asked to write a brief structure of F, G, H, I, and K, and describe the specific reaction types of D→F, F→G, G→H, H→I.

Hiss~

Mr. Liu's ancestral chemistry question is so complicated, so difficult, and so greasy!

The students frowned, unable to sort out for a while.

“Good。 Liu Hualong smiled slightly, he was very satisfied with the stupid expressions of his classmates.

Good？

The students are not good, I don't know where to start with this question, what is there to be good about?

Bad！

Terry Thin!

Sister Knight!

"This is a college entrance examination question, I came out. Liu Hualong inadvertently revealed a shocking secret.

The students were in awe.

Teacher Liu, the boss of the college entrance examination question committee!

Teacher Liu, a peerless master hidden in the sheep!

Teacher Liu is not a thing in the pool, and he will turn into a dragon when the wind and clouds meet!

Hiss!

"To be exact, this is the alternate finale question of chemistry in the college entrance examination in a certain year, although this question has never appeared in the previous college entrance examination papers, but it cannot be ruled out that it may appear in the future. ”

Liu Hualong was both regretful and full of expectations, he continued: "Students must not be confused by the complex question, the central idea of this question is only one sentence: under the action of fluoride ions, the elimination reaction of o-trimethylsilylphenol trifluoromethanesulfonate is a typical method for the synthesis of benzyne. ”

"Familiar, unfamiliar? Of course familiar, of course, familiar, phenylyne, nucleophilic addition, nucleophilic substitution, pericyclic reaction, and other basic knowledge, I just told you last week, fresh and delicious, you can eat it as soon as it is hot. ”

"18-Crown-6 acts as a coordination agent for potassium ions and enhances the nucleophilicity of fluoride ions. As an electron-deficient system, phenyne is susceptible to nucleophilic attack by alcohols, amines or their corresponding negative ions. In nucleophile E, the amino group is the most reactive nucleophilic site, and it is not difficult to infer that the nucleophilic addition reaction between the two is used to obtain G. ”

"So the question is, is the intermediate here the zwitterion G', or the product G after the proton transfer has occurred?"

Liu Hualong paused for a moment when he said this.

Ranger blurted out, "It's G!"

Liu Hualong asked: "Lan Jie, please give me a reasonable explanation." ”

Lan Jie deduced while listening to the lecture, he had not yet deduced the simple structure of I, but he felt that G had already been manipulated by him: "According to the basic knowledge of atomic and molecular structure, it can be known that the rate of proton transfer is much greater than the nucleophilic substitution reaction on acyl carbon, so G undergoes nucleophilic substitution reaction on acyl carbon to obtain H, which is also the aromatic electrophilic substitution reaction of benzene ring." ”

Liu Hualong nodded and said: "Good, Lan Jie has always been clear-minded, logical and responsive, and there is no problem with his positive explanation, it is indeed G." I would like to add that the reverse deduction method, the molecular formula of H is a known condition, and for experienced students, the simple formula of the structure of H is also a known condition, and H not only contains electron-rich group tertiary amines, but also contains ......"

Hisss hiss!

Many students looked at Lan Jie in the corner of the last row.

Applejack is in a stable state, steady and progressive, and his dominance in chemistry is not inferior to that of physics and mathematics!

At this time, Lan Jie was immersed in the study of LUMO and HOMO, his understanding of chemistry was getting deeper and deeper, and chemistry brought more and more fun, and chemistry was qualified to be promoted to the top tool.

“...... So I is an allyl derivative, and it can be seen that the reaction to get I is an alkene reaction. Liu Hualong patiently explained step by step, in-depth layer by layer analysis, he said: "There is a π bond in the carbon-carbon triple bond of benzyne formed by the sp2 orbital through the weak overlap of the side, which is much weaker than the π bond of ordinary olefins and alkynes. You now understand that compared to olefins and alkynes, benzyne has a lower LUMO energy and is more susceptible to nucleophilic attack. ”

"The truth is revealed, let's make a summary, although the knowledge points involved in this question, such as phenylyne, nucleophilic addition, nucleophilic substitution, and pericyclic reaction, are basic knowledge, but when examined together, the difficulty of the test center increases exponentially. This type of question, which I call the 'basic comprehensive problem', is a simple basic knowledge that is difficult to synthesize.

"When dealing with the 'basic comprehensive problem', students can adopt a roundabout tactic, first use the method of pushing arrows to make a reasonable guess about the structure of the product, and then rationalize the chemical mechanism written, and then go back to check whether there are loopholes in the simple idea at the beginning, which chemical process is more reasonable, so as to make corrections and get the correct answer. ”

"What? I didn't understand the basics? Are you kidding me? Are you kidding? You took my Liu Hualong's chemistry class on the first day?"

"It's the second semester of high school, and you still expect me to repeat the basics with you? Why are you so naïve?

"Lan Jie, you are a member of the study committee, this classmate has been handed over to you, you communicate with him. Class. ”

The bell rang for the end of class, and Teacher Liu left the classroom.

Lan Jie hooked his fingers: "Huang Yuhang, please come over for a moment." ”

Huang Yuhang's classmate reluctantly sat in Lan Jie's deputy seat, and he said embarrassedly: "Brother Jie, you also know that I have a weak foundation and a weak foundation, and compared with you righteous sheep students, I have more difficulty learning. ”

Lan Jie asked with concern: "Yuhang, you mentioned to me last time, your school status is in the sweet potato area, right?"

"Well, in the sweet potato area, I'm a native sweet potato boy. ”

"It's quite far from the sweet potato area to Yangzhong, you don't live in the school, right? You squeeze the subway to and from Yangzhong and the sweet potato area every day, will it be very hard?"

"My family has a house near Yangzhong, and I ride my bike to and from school, and it is not hard. ”

"Yuhang, which neighborhood is your house in?"

"Over the mountain coast. ”

"Oh, it's not far, seven or eight minutes by bike, and your community is safe and well-managed, then I'm relieved. Astronautics, are you studying and living here, are you used to it, are you adaptable?"

"Thank you Brother Jie for your concern, I am quite accustomed to life, and I am indeed a little uncomfortable in learning. ”

"Okay, I know, I'll communicate here today, and I'll go to your house in a few days to find out the actual situation. ”

"Welcome, Welcome, Brother Jie, you must come!"

Huang Yuhang felt the warmth of the organization, and he regained his confidence and left the classroom to have lunch.

At this time, Li Zihan turned his head and said, "Why is it difficult for H and F to have a Diels-Alder reaction?"

Lan Jie was quite surprised: "Yo, Brother Hanzi is talking to me?"

"Don't talk nonsense, hurry up and tell me why. ”

"I'm not surprised, I'm not surprised, Brother Hanzi actually took the initiative to ask me chemistry questions!"

"There's a lot of trash talk. Li Zihan stood up and left.

Lan Jie smiled and patted the sub-desk desk: "Sit down." ”

Li Zihan moved two steps sideways to the aisle, without the slightest intention of being obedient.

"Li Zihan, I'll let you sit down!"

"What a fierce one!" Li Zihan sat aggrievedly in Lan Jie's second seat.

Lan Jie said softly: "Eat lunch together, go to eat outside the school, I invite." ”

Li Zihan shook his head decisively: "I said that I like to eat in the dining hall." ”

"Don't give it a chance?"

"This ......"

"Am I not decent enough?"

"Heh......"

"Embarrass me, Applejack?"

"Hey......"

"Lunch together outside the school?"

"Oh......"

Ranger spread out his draft book and gave what he thought was a reasonable explanation: "MeOH would not have been possible if the Diels-Alder reaction had been routed. In addition, α, β-unsaturated ketone is also an electron-deficient system, so the Diels-Alder reaction with benzyne is difficult to occur. This is my unilateral remark, and the final conclusion is subject to Mr. Liu's interpretation. ”

"Oh, that's right, your one-sided remarks seem to be reliable. Li Zihan suddenly realized, his eyes flashed with electricity and light, and his chest spewed the power of knowledge.

Lan Jie said sincerely: "Our class finally gave birth to a brother who can communicate with me on an equal footing, Zihan, I cherish our brotherhood, I hope you can cherish it too." ”

Li Zihan beeped quietly: "It's not that I don't understand Diels-Alder's reaction to this knowledge point, it's just that I didn't turn a corner all of a sudden, don't talk about any brothers, who is a brother with you?"

"Hey, hey, hey. Lan Jie laughed heartily, and then went to the porridge noodle shop outside the school with Li Zihan.

The two ate thirty yuan, and Li Zihan insisted on AA.

"Lan Jie, one yard to one yard, this meal can't be asked for you, AA, I'll pay for my own bowl of wonton noodles. ”

"Li Zihan, are you going to make trouble?"

"Lan ......"

"Sit down, put away your phone, put your hands behind your back, and be honest!"

The upright Lan Jie said that he would definitely invite someone to dinner, he tied Li Zihan to a chair, and then went to the counter to pay the full amount.