Cisisomer: Two identical atoms or groups on the same side of a double bond or ring are cis isomers, also known as cis.
Trans isomer: Two identical atoms or groups on both sides of a double bond or ring are trans isomers, also known as trans.
Production conditions:
At least one bond in the (1) molecule cannot rotate freely (otherwise it will become another molecule);
⑵ Double bonds cannot have the same group on the same carbon.
speciality
Isomerization refers to the same molecular formula but different structural formulas, and cis-trans isomerization refers to different spatial conformations. So cis-trans isomerization belongs to isomerization.
If two carbon atoms on a double bond are connected to four completely different atoms or groups, then the two atoms or groups connected to each carbon atom are compared according to the "order rule". If the two better groups are on the same side of the π bond plane, they are Z isomers, and those on the other side are E isomers.
Order rule
(1) is determined by the atomic numbers of two atoms directly connected to the carbon of the double bond, and the larger the atomic number, the better. If the atomic numbers are the same, compare the relative atomic masses.
(2) If the first atom directly connected to the double bond carbon atom is the same, the second or even the third atom should be compared in turn, and so on until the priority order is compared.
Note: Shun, reverse, Z and E are two different labeling methods. Shun is not necessarily Z-shaped, but reverse is not necessarily E-shaped.
Reflective composition 300 words
In the just-concluded mid-term exam, I made many mistakes that I shouldn't have made.
My Chinese has always been good, but this time, due to some strange coincidences, I made many mistakes in Chinese.
After careful reflection, I think this has a lot to do with my carelessness in reading the topic.
This also extends to math and English.
Many small mistakes in calculation and grammar cost me a lot of points.
I know the teacher expected a lot of me, but I still didn't do well in the exam.
I'm very sorry about that.
But since you made a mistake, you have to correct it. So, I also thought a lot about what I must learn after the exam.
First of all, I want to get rid of the bad habit of not looking at the questions carefully in the exam.
Sometimes I often look at the front of the topic and write the following questions conveniently, but there are many mistakes.
This may also have something to do with answering skills.
In a word, through the later practice, I must carefully examine the questions in the exam, look at the questions by myself, and see the questions clearly and optimistically.
Check it several times when time permits, and never allow yourself to make unnecessary mistakes like this again.
Secondly, I will strengthen the practice of Chinese, math and English, as well as politics, history, geography, biology and physics.
After the exam, I finally understand that there are mountains outside the mountains and people outside.
On weekdays, everyone gets together to do the same topic, and there is no obvious difference.
But as soon as I took the exam, I found that there were so many questions that I had never seen before.
Only blame yourself for not exercising enough.
I can't allow myself to continue like this, so I must redouble my efforts, learn from this exam, increase my strength, prepare for the next exam and lay a good foundation.
00 exam skills are being practiced.
In life, I should practice and review more, and make a comprehensive review plan before the exam, so I don't have to be impatient and have no direction.
Learn to accumulate good words and sentences in daily life and study, and accumulate difficult topics in mathematics. English is a grammar project.
Doing cloze and other exercises is also a good way to improve English.
After all, the mid-term exam is not the final exam, but I still have a chance.
In the next exam, I will work harder and try not to disappoint my teachers, parents and classmates.
Don't disappoint yourself.
Ahem, you can change it yourself below. After the exam, students are most concerned about the results of various courses.
In fact, the score is only an evaluation of your efforts at this stage. Don't stare after the exam. The key is to find out the reasons for losing points and make up for the shortcomings at this stage in time.
The process of learning is the process of constantly discovering and solving problems.
Behind the unsatisfactory results is the exposure of problems. We must immediately sum up our reflections and take measures to remedy them, so as to create more glories in the future final exams, senior high school entrance exams and college entrance exams.
As an examination reflection, the first reflection is the usual learning attitude.
If you lose too many points on memorable topics in the exam, especially on memorable subjects (such as biology, geography, basic Chinese and English), it is obviously a problem of insufficient investment and learning attitude.
If there are many mistakes in many simple knowledge applications and lack of calculation ability, it means that there is not enough training at ordinary times, which is also a problem of learning attitude.
Reflect on whether you have consciously studied and reviewed at ordinary times; Are you lucky enough to think that procrastination is nothing, as long as you are careful a few days before the exam.
Reflect on whether you study blindly. Some students just knock around for a day. Some students have many plans and goals every day, but none of them can be achieved at the end of the day.
Reflect on whether your study is solid, whether new knowledge only stays at the level of understanding and memory, and whether you have mastered and applied it.
Most students have a little knowledge and don't know how to write when solving problems.
In fact, learning attitude is the premise that determines your grades. If you want to get good grades, you must have good study habits and correct learning attitude.
Secondly, students should reflect on the mastery of examination skills.
Every exam can always find that some students lack certain exam skills, such as: I feel that the exam time is not enough, my handwriting is scrawled, and I can't even see myself clearly; The answer is written in the sealed line, which can't be seen by binding; Some students even found their own way, starting with the last question and so on.
As the basic common sense of examination, habits such as easy before difficult, standardized writing and reasonable allocation of time should be exercised in the usual unit examination.
Third, students should also reflect on their examination mentality.
At the end of every exam, there are always classmates who say that they are too nervous to play well.
This is the problem of examination mentality.
Some of them are so eager to express and show themselves that they are too arrogant; Have you studied hard according to the teacher's request and are afraid of the exam?
Without a good attitude, you can't play a normal level.
When taking an exam, paying too much attention to scores and rankings will undoubtedly increase the sense of tension and affect the effect of the exam.
If you take the exam as a way to find problems and facilitate future study, you will not be nervous. On the contrary, you will like exams and use them as a means to test your learning effect.
In fact, the process is the most important, as long as you do your best in the process, you are not afraid of no results.
There is a road to success, and there is a reason for failure.
A fall into the pit, a gain in your wit.
It is important to summarize and reflect after the exam, but it is more important to find a new starting point. Some students will collapse if they fail the exam once. I don't think it is necessary to do so. We should be a strong learner, find our starting point again, and firmly believe that we can see the rainbow without wind and rain.
With a good mood, with a normal heart into the next round of learning, I believe that as long as you pay, there will be a return.
With a new starting point, we must go forward bravely and strive for new goals.
Some students are very motivated after taking the exam, making a lot of review plans and making a lot of resolutions, but in a few days they will be the same as before, so perseverance is very important in the process of learning. If you don't make changes like before, you will be afraid of falling out of Sun Shan in the next exam, just like 0, when you don't draw a 1 in front, 0 is still 0.
Reflective composition of 300 words in junior Chinese.
The reflection on the tense Chinese exam is over, and the success or failure of the exam is still an unsolved mystery. However, when we finished the last class, the teacher's brief words turned into a bolt from the blue, which made us feel as relaxed as frosted eggplant! However, the teacher gave us a judgment paper and told us that I dropped a lot of points in the second, sixth and seventh questions in the reading of the paper, which made me feel uncertain, because I kept writing typos, and one question added the word "Gao" to the radical to form new words, so I didn't pay attention to such questions at ordinary times, which led to the irretrievable exam! Alas! The exam has passed, and the mistakes in the exam are irreparable. We can only pay attention to it later and correct it.
I will do the questions carefully in the future and check them carefully after I finish.
I want to accumulate more wrong questions, analyze the causes of wrong questions, compare the correct answers, and better master the rich basic knowledge of Chinese and use it flexibly.
The exam questions are changeable, so we should not only accumulate them, but also use them flexibly in order to cope with them freely.
A few days ago, our class took a Chinese exam.
It was noon at that time, and the teacher came unexpectedly, taking advantage of people's danger.
But soon, the paper was sent out.
I can't believe there isn't even a person with a 95 in our class.
We are all surprised at this.
I have been reflecting on why I didn't do well in this exam, and finally I came to the following conclusion: 1: We always forget to do the questions carelessly during the exam.
The most important thing is that we do it slowly, although some people do it quickly.
However, people who do it slowly still do it slowly. Many people were rushed to hand in their compositions before they finished writing them.
(I sympathize with this) 3: We are always careless in doing problems and always make mistakes. It can be said that it is the countdown of the class.
This is definitely more wrong than right.
Think about it, we always leave the questions behind and generally don't look them up.
How many people can check? Even if you can check it, you won't check it carefully.
5: There is also that when we write, we always write incompletely, and we will write badly.
It's not like I thought about it before I wrote it.
These are just a few. I think people in our class should know better than me why they didn't do well in the exam.
Class cadres reflect on 300-word composition
I made a mistake this time. I thought a lot and reflected on many things. I'm sorry, and I'm very angry with myself, because I broke the iron law of the school. I am also deeply aware of the seriousness of my mistakes and feel ashamed of them.
At the beginning of school, I repeatedly emphasized the school rules and discipline to remind students not to violate the school rules, but I didn't pay attention to what the school and teachers said, what the teachers said, and what the school promulgated. None of this should be.
It is also disrespectful to the teacher.
You should remember what the teacher said and the school rules and regulations promulgated by the school.
Thoughts and suggestions on 300-word composition
In the afternoon, in the third period, everyone plays in the class. They didn't seem to hear the class at all, but they were still running and slapping. The noise in the classroom can be imagined.
I'm not immature and tasteless like them. As usual, I sat in my seat reading and didn't pay attention to the things around me.
After a while, teacher Zhang came in angrily and passed me. I'll put the book away at once.
I saw teacher Zhang put the book down and said, "You can't have Chinese class yet!" " "Everyone immediately quiet down.
Of course, it was followed by severe criticism.
Listening to the teacher's reprimand and feeling the teacher's painstaking efforts, I can't help feeling a little cold.
The teacher is also very hard, so don't treat her like this! Once, when I was handing in my homework to my teacher, I saw that one of the watches in my class and Class Two was midnight.
There are hundreds in all.
So many, when will the teacher change! The hard work of homework can be imagined.
But we, on the other hand, added fuel to the fire. Some students don't obey the discipline and don't finish their homework, which is very hateful. This is disrespectful to teachers and immoral!
Reflection on 300 words
The reasons why I didn't do well in this exam are summarized as follows: 1 I didn't develop the habit of being meticulous at ordinary times, and I was careless in answering questions during the exam, which led to many questions being deducted or even not done correctly.
2 inadequate preparation.
Chairman Mao said, don't fight unprepared battles.
The implication is that it is difficult to win an unprepared battle, but I didn't act according to this wise saying, which led to my failure in this exam.
3 did not solve the contradiction between interest and course study.
I have many interests. As a person, a complete person, an understanding person, of course, I should not let my interests be erased for no reason, just like a machine, not only sad, but also ignorant. But if you seriously delay your study because of your interest, it will be bad, not only bad, but sometimes it is really not worth the candle.
What if I fail? Serious reflection is the first: first, what is the reason for this failure? We should seriously think about it and dig up the root causes; Second, what are you going to do next? Determine your own goals, don't be unwilling to go on because of failure, and measure yourself correctly.
See what you want, where are your strengths and what are your weaknesses; Third, determine the goal.
Know what you want, make a plan, step by step.
Failure is not terrible, what is terrible is collapse and blind pursuit.
Mathematics is one of the compulsory subjects, so we should study it seriously from the first day of junior high school.
So, how can we learn math well? This paper introduces several methods for reference: First, pay attention to the lecture in class and review in time after class.
The acceptance of new knowledge and the cultivation of mathematical ability are mainly carried out in the classroom, so we should pay attention to the learning efficiency in the classroom and seek correct learning methods.
In class, you should keep up with the teacher's ideas, actively explore thinking, predict the next steps, and compare your own problem-solving ideas with what the teacher said.
In particular, we should do a good job in learning basic knowledge and skills, and review them in time after class, leaving no doubt.
First of all, we should recall the knowledge points the teacher said before doing various exercises, and correctly master the reasoning process of various formulas. If we are not clear, we should try our best to recall them instead of turning to the book immediately.
In a sense, you should not create a learning way of asking questions if you don't understand. For some problems, because of their unclear thinking, it is difficult to solve them at the moment. Let yourself calm down and analyze the problems carefully and try to solve them by yourself.
At every learning stage, we should sort out and summarize, and combine the points, lines and surfaces of knowledge into a knowledge network and bring it into our own knowledge system.
Second, do more questions appropriately and develop good problem-solving habits.
If you want to learn math well, it is inevitable to do more problems, and you should be familiar with the problem-solving ideas of various questions.
At the beginning, we should start with the basic problems, take the exercises in the textbook as the standard, lay a good foundation repeatedly, and then find some extracurricular exercises to help broaden our thinking, improve our ability to analyze and solve problems, and master the general rules of solving problems.
For some error-prone topics, you can prepare a set of wrong questions, write your own problem-solving ideas and correct problem-solving processes, and compare them to find out your own mistakes so as to correct them in time.
We should develop good problem-solving habits at ordinary times.
Let your energy be highly concentrated, make your brain excited, think quickly, enter the best state, and use it freely in the exam.
Practice has proved that at the critical moment, your problem-solving habit is no different from your usual practice.
If you are careless and careless when solving problems, it is often exposed in the big exam, so it is very important to develop good problem-solving habits at ordinary times.
Third, adjust the mentality and treat the exam correctly.
First of all, we should focus on basic knowledge, basic skills and basic methods, because most of the exams are basic topics. For those difficult and comprehensive topics, we should seriously think about them, try our best to sort them out, and then summarize them after finishing the questions.
Adjust your mentality, let yourself calm down at any time, think in an orderly way, and overcome impetuous emotions.
In particular, we should have confidence in ourselves and always encourage ourselves. No one can beat me except yourself. If you don't beat yourself, no one can beat my pride.
Be prepared before the exam, practice routine questions, spread your own ideas, and avoid improving the speed of solving problems on the premise of ensuring the correct rate before the exam.
For some easy basic questions, you should have a 12 grasp and get full marks; For some difficult questions, you should also try to score, learn to score hard in the exam, and make your level normal or even extraordinary.
It can be seen that if you want to learn mathematics well, you must find a suitable learning method, understand the characteristics of mathematics and let yourself enter the vast world of mathematics.
I finished the Chinese exam, but the exam results made me sad, worried my teachers, chilled my parents, worried everyone who thought I was good, and worried them, which made me sad and sorry for my conscience.
Last semester, my teacher paid a lot for me, especially Mr. Zhang, so I think I must study hard this semester, even for others, so I did well at the beginning of the semester, but I can't change my previous bad habits. I still have some shortcomings, such as empty talk in class, nonsense after class, careless homework and inattention in study.
In terms of Chinese, I didn't make much effort, just asking myself to recite ancient Chinese. My attitude in class is no different from before, so all the blanks in my test paper are correct, but there are many mistakes in the meaning of words, which is probably the reason.
How time flies! In a blink of an eye, the exam is over and the papers have been handed out. Looking at the score on the test paper, I was surprised, because it was not what I really wanted. Why can't I get a higher score? So I began to check myself. I didn't listen carefully at ordinary times, and I didn't pass geography. To this end, I have come up with several ways. 1) Before doing the problem, always remember that there is another ""; 2) When solving a problem, don't rush to write, first list the main steps of this problem on the draft paper, and then step by step, don't ignore every detail, and try to answer every question completely and beautifully; 3) Do more different types of questions at ordinary times, so that when you get the test paper, you will be familiar with most of the questions and be more sure; 4) Do some calculation exercises properly to avoid losing points in calculation. I think if I can do what I mentioned above, I can. ...
The composition of Reflection on Fighting is about 300 words.
After deep self-reflection, I decided to take the following personal rectification measures: 1. Submit profound self-criticism as required, dig deep into the root of your own ideological mistakes, and realize the possible serious consequences.
2. The ideological consciousness is not high, and the importance of important things is seriously insufficient.
Even if there is understanding, it has not really been put into action.
3. Strengthen communication with classmates, monitor and student union cadres.
Promise not to violate school rules and regulations in the future.
4. Respect the teacher, and don't talk back to the teacher at any time and anywhere.
5. Raise awareness, pay close attention to implementation and vigorously carry out criticism and self-criticism.
At present, the whole school is at the peak of making every effort to build an excellent class spirit, but I have a very disharmonious tone-fighting.
This incident has had a bad influence on our class.
On the one hand, it shows that I don't study hard enough, on the other hand, it shows that I don't know enough about this job.
I feel deeply guilty and sad for delaying the construction of excellent class spirit in our class this time.
I admit that I should bear the unshirkable responsibility for this fight.
At the same time, it also reveals that the understanding of observing the school spirit and discipline is not paid enough attention.
6. If you are ashamed, change it, mend it, and pay close attention to implementation.
I want to take this fight as a mirror, check myself from time to time, criticize and educate myself, and consciously accept supervision.
At present, the whole class is carrying out activities to create class atmosphere. As a member of the class, I should be alert to shame, forge ahead with shame, mend after it is too late, pay close attention to implementation, turn shame into motivation and study hard.
Make due contributions to our class with practical actions, and make up for the shortcomings and shortcomings in my past study with my own efforts.
I want to improve my ideological understanding and strengthen my responsibility measures through this incident.
I have the determination and confidence to learn better! Now that I have realized my mistake, I plan to correct my bad habits in the future, insist on not fighting, adjust my mentality and make progress every day! Thank you very much for correcting my mistakes in time. I promise that similar behavior will not happen to me in the future, and I am determined to do my bit for the safety work and evaluation work of our school.
Please care about our teachers and classmates, continue to supervise and help me correct my shortcomings, and let me make greater progress! I hope teachers and classmates will help me in my future work, life and work, help me overcome my shortcomings and correct my mistakes.
In order to dig out the root of my ideological mistakes, I have made a very profound reflection and review here.
I sincerely hope that I can have a chance to correct it.
Ask teachers and students to supervise more.
I believe that the teacher can see my attitude and know that I have a deep repentance attitude towards this matter. I believe in my confession. My behavior is not a challenge to the teacher's discipline, but my own momentary negligence. I hope the teacher can forgive my mistake, and I assure you that it won't happen again.
Reflection on growing up and writing 300 words
Most people want to change the world, but few people want to change themselves.
In fact, it is better to calm down and reflect on yourself and make your life more perfect.
Many times, we expect to get more returns from the outside world.
Expect things around you to be more satisfactory; Expect friends around you to be more friendly to themselves; I hope my study can always be among the best; I hope my future will be better … but when we face the reality, we often become lost and negative because of various disappointments.
But through introspection, it is not difficult for us to find that all the reasons are actually caused by our own failure in a certain aspect.
Sometimes, at the end of the exam, I always complain when I look at my grades.
In fact, after careful reflection, I found that it was actually because I didn't master the knowledge points.
If you master these knowledge points before the exam, you will not be so impetuous after the exam.
Sometimes when I am writing my homework, I hope to finish it quickly and ignore the quality.
Occasionally decided to slow down the writing speed and ensure the quality.
Finally, I found that there was little difference between the methods of doing homework before and now.
Although it's only ten minutes, by comparing the quality of homework, I find that there is a world of difference between the two.
Some people want to change the world, but find it difficult; So I decided to start changing my country, but it is still difficult; It is too small to change only the people around you, but it is still difficult; Finally, when he calmed down and reflected, he found that when he changed himself, the people around him would also be affected and changed, thus affecting the country and the world.
In fact, all this is achieved through self-reflection, self-examination and correction of shortcomings.
In life, we should always reflect on ourselves to make our life more perfect and full.
The seventh grade final exam math reflection composition 300 words.
I know the teacher expected a lot of me, but I still didn't do well in the exam.
I'm very sorry about that.
But since you made a mistake, you have to correct it. So, I also thought a lot about what I must learn after the exam.
First of all, I want to get rid of the bad habit of not looking at the questions carefully in the exam.
Sometimes I often look at the front of the topic and write the following questions conveniently, but there are many mistakes.
This may also have something to do with answering skills.
In short, through later practice, I must carefully examine the questions during the exam, carefully read the questions and fill in the contents accurately.
If time permits, check it several times more and don't allow yourself to make similar mistakes again.
Secondly, I also want to strengthen the practice of Chinese, math, English and physics.
Through the exam, I learned about everyone's strength and the truth that there are mountains outside the mountains and there are people outside.
On weekdays, everyone gets together to discuss research problems, and there is no obvious difference.
But after the exam, it is not difficult to find that there are so many questions that I have never seen before.
Alas, I only blame myself for doing too little exercise.
I can't allow myself to go on like this, I must redouble my efforts.
I will learn from the lessons of this exam as a foreshadowing, lay a good foundation for the next exam and get ready.
Practice is the key to exam skills.
In life, I should practice and review more, and make a comprehensive review plan before the exam, so I don't have to be in a hurry and have no learning goals.
Learn to accumulate and use on weekdays, and Chinese should accumulate some beautiful words and beautiful fragments; Mathematics should practice more difficult problems and recite more key points; Physics should do more experiments, recite theorems and practice language organization ability; English is the focus and difficulty of grammar, and practice is also a good way to improve English.
I want to say to the teachers: "I hope the teachers will not lose confidence in me." Although I didn't do well in this exam, I believe in myself and can break through myself. "
I'll try my best in the next exam! Please believe me. "
Running practice and reflection on 300-word composition
This afternoon, after the second class, we are going to run aerobics, but it's too hot for me to go. I have no choice but to go.
If we don't go, the teacher should punish us.
I have to go running.
Start running. I don't feel tired when I start running. After a while, I became more and more tired, and my tired hand kept flowing downwards. It's too hot! Finally stopped.
I ran to the hose and washed my hands and face.
After that, it was not so hot. I went to the classroom to sit for a while.
I am not hot at all.
It's too hot today! However, insisting on running and exercising all the time is equivalent to exercising.
Our bodies will be very healthy! We must persist, and persistence is victory! Come on!
Practice and reflect on 300-word composition on duty
In the morning, the students on duty are very busy outside our school. It is not primary school students who enter the school gate, but students who arrive early to avoid the students on duty.
School regulations: you are not allowed to go to school before 7: 30 in the morning, but many students leave home early (including me, of course) and get to school early if there is no place.
At the crossroads, we met the first "checkpoint". Naturally, there is a student on duty "guarding" here, and we can't pass until 7: 25.
Many students couldn't wait that long, so they went in droves, and I followed, thinking: this student on duty can't remember so many names.
As we passed the crossroads, some bold students began to try to move forward.
I didn't go with them this time. Let them become "pioneers". It's not too late for me to leave until I'm sure there are no problems.
I was thinking about it when I saw some students on duty arrested.
Look at the students behind, they have fled everywhere, and I quickly "escaped" to the north.
Finally, at 7: 25, we passed the first "checkpoint", and the next "checkpoint" was Xinhua Bookstore. Several students on duty were "guarding" and the students were afraid to cross it easily.
There are always some bold students who walk forward cautiously.
This walk was discovered by the sharp-eyed students on duty.
The students on duty came towards us and we scattered, but the students on duty followed us.
As a result, a fierce "dare you to arrest me" officially kicked off.
We are a group of timid mice, but the students on duty are cunning cats.
After several rounds of "hunting", we all hid in the past, and the "cat-and-mouse war" was going on fiercely ... At this moment, the school song sounded, and the students in the "cat-and-mouse war" seemed to hear the instruction of "truce" and stopped fighting.
The students rushed into the campus and the quiet campus immediately became lively.
Please indicate the source for reprinting. What do you mean by "shun" and "reverse"?