The resonance effect in the sociology of the resonance effect

1. In physics.

It refers to the situation when a material system vibrates with a greater amplitude than other frequencies at a specific frequency; These specific frequencies are called resonant frequencies.

At the resonant frequency, a small periodic drive force can produce a large vibration, because the system stores the energy of the vibration as a damper. There is a very small chance that the resonant frequency will be approximately equal to the natural frequency or natural frequency of the system.

The latter is the frequency of free oscillation, and the difference between the two is only the difference in the recovery force, the recovery force of the resonance frequency includes gravity, electromagnetic force and other forces, while the recovery force of the natural frequency only comes from gravity.

2. In chemistry.

For molecules, ions, or free radicals whose structure cannot be expressed by one classical structural formula, their structure can be expressed by the resonance of several classical structural formulas.

The structure in resonance does not exist, and the real particle is not a mixture of these resonance structures or an equilibrium system, but the structure of matter cannot be accurately expressed by a single structural formula in the theory of valence bonds, and the idea of resonance must be used.

1. The identification is different.

The most important property of the pendulum in the resonance effect is that it oscillates at one frequency, commonly known as the natural frequency. When it is excited by external interference, its corresponding oscillation law depends on whether the interference frequency is consistent with its hope.

The conjugation effect is an electronic effect in which the distribution of electrons (or p electrons) in the conjugated system changes due to the interaction between atoms.

2. The process is different.

When some molecules, ions or free radicals cannot be explained by a single structure (energy value, bond length, chemical properties), we use two or more structural formulas instead of the usual single structural formula, this process is called resonance.

Where the substituents on the conjugated system can reduce the electron cloud density of the system, then these groups have an electron-withdrawing conjugation effect, which is denoted by -c, such as -cooh, -cho, -cor; Where the substituent groups on the conjugated system can increase the electron cloud density of the conjugated system, then these groups have an electron conjugation effect, which is denoted by +c, such as -NH2, -R, -OH.

The resonance effect is the continuation and development of the conjugation effect, which also includes the conjugation effect and the superconjugate effect. They are both reporting effects of a substituent through an electronic system, and in many cases, the induction effect and the resonance effect are often at work at the same time, so they are often combined and called electron effects, but they have different meanings.

All vibrations must be manifested in the form of displacement, and behind them must be the flow of energy. The fundamental reason why resonance is so powerful is that resonance causes external forces to act directly at the molecular or atomic level (or some other specific level), and continuously absorb energy, causing it to undergo a small range of violent displacements. If the external frequency is inconsistent with the natural frequency, then the object of the external force is the whole object, but if it is consistent with the natural frequency, then the object of action directly becomes a molecule and atom, and the resonance destroys the unity between the particles, making them fight with each other, and the result is that the whole system collapses instantly.

From the perspective of the pendulum, a macroscopic vibration system, if the pace of the external force is the same as the natural frequency of the pendulum (for example, when the pendulum always moves to the highest point, the pendulum is given an oblique downward force), then the pendulum will continue to absorb external energy. The external energy is completely absorbed every time, and the pendulum does not export any energy to the outside world, so the energy possessed by the pendulum itself increases dramatically. If the pace of the external force is inconsistent with the pendulum, then the energy absorbed last time may be offset by the external force next time, and the gravitational potential energy of the pendulum itself will also be offset by the external force from time to time, which makes the energy of the pendulum itself always remain at a fluctuating level, and the peak value will not be too high, and the energy is repeatedly absorbed, lost, absorbed, and lost.

In short, the power of resonance lies in the fact that the external force acts on the most microscopic level (or specific level) of the object in the most precise way (or rhythm), so that each basic unit of the object (such as pendulum, atoms, molecules) at that level continuously absorbs energy like cancer cells, and then undergoes violent displacement, and finally has a great destructive effect at this level.

The process of resonance is similar to a strong positive feedback process that can cause the system to expand violently in a short period of time.

The phenomenon of resonance refers to the tendency of a physical system to absorb more energy from its surroundings at its natural vibrational frequency (so-called resonant frequency). There are many places in nature where there is a phenomenon of resonance. Humans are also using or trying to avoid resonance phenomena in their technology.

Some examples of resonance are: the acoustic resonance of musical instruments, the orbital resonance between the moons of some Jupiter-like planets in the solar system, the resonance of the basement membrane in the animal ear, the resonance of electrical circuits, and so on. Generally speaking, a system (whether mechanical, acoustic or electronic) has multiple resonant frequencies at which it is easier to vibrate and more difficult to vibrate at other frequencies.

If the frequency that causes the vibration is complex (e.g. an shock or a wideband vibration), a system will generally "pick out" its resonant frequency to vibrate with that frequency, and in fact a system will filter out other frequencies.

The resonance theory was put forward by American chemists in the early thirties of the nineteenth century, a theory of molecular structure, he believed that the real structure of the molecule is formed by the resonance of two or more classical valence bond structures, and the resonance theory includes the concepts of delocalized bonds, bond lengths, bond energies, etc., representing the electron delocalization of electrons by resonance.

The advantage of the resonance type is that the electronic formula can be used to characterize the distribution position of the charge in the electron delocalization system, which is convenient and practical to describe. When a molecule or ion can write more than two Lewis structural formulas according to the valence bond rule (their difference is only the distribution of bonds or electrons, while the position of the nucleus does not change), then the real molecular structure is the resonant hybrid of these structures, that is, the real structure of the molecule is the resonant hybrid, and the resonant hybrid has the characteristics of the sum of the above structures, but no resonant structure can represent the molecule alone; Nor can the individual resonance structures exist on their own.

Where a molecule or ion has a resonance, it is more stable than that without a resonance, and the more structures participating in the resonance, the more stable the hybrid is; In particular, if the formula with the same structure participates in the resonance, the hybrid is the most stable.

Among the various resonance formulas, the formula with the lowest energy and similar structure accounts for the most probability, taking allyl cation as an example

The concept of resonance energy is a procedure that indicates that a resonant hybrid is more stable than any single resonance structure.

3.To write the resonance structure correctly, the following rules should be followed:

Only the movement of bonds and electrons is allowed between the resonance structures, but not the change in the position of the nucleus.

All resonance structures must conform to the Lewis formula.

All resonance structures must have the same number of unpaired electrons. Take allyl free radicals as an example:

ch2=ch-ch2→ch2-ch=ch2。

Electron delocalization tends to make the molecule more stable and has a lower internal energy, and in order to measure this stability, the so-called resonance energy can be used The so-called resonance energy is the difference between the energy of the actual molecule and the energy of the most stable resonant structure possible, taking the benzene molecule as an example. In the resonance structure, the lower the energy of the covalent bond and the more stable it is, and it has a greater chance of being in the hybrid. The real structure of benzene is a resonant hybrid composed of eight structural resonances, it should be pointed out that in the above example, all the formulas should be square side-shaped carbon rings in a plane, and there can be no variation, these resonance structures are actually hypothetical structures, and the difference between them is only in the structure where the electron distribution is not assumed, and the difference between them is only in the difference in the electron distribution, therefore, the energy of each resonance formula is not all the same.

The structure of the I and II types is similar, the energy is the lowest, the energy of the other resonant types is relatively high, and the resonance formula with the lowest energy and similar structure participates the most in the real structure, or contributes the most, so it can be said that the real structure of benzene is mainly the resonance hybrid of the I and II types.

All the atoms in the structural formula have a complete valence electron shell and are relatively stable.

The stability of charge separation is low.

The negative charge is more stable on atoms that are more electronegative.

The resonance effect is the continuation and development of the conjugation effect, and the resonance effect also includes the conjugation effect and the superconjugate effect. They are both substituents through the electronic system of the reporting effect, in many cases, the induction effect and the frank resonance effect often work at the same time, so they are often combined and called the electron effect, but they are not the same thing.