College chemistry questions, hoping to give the correct answer and give a way to judge the stability

Look at the carbocation on the connected group.

1.If an alkyl group, H, etc. is linked, since the carbocation is sp2 hybridized, there is a vacant P orbital, which will form a superconjugation with the c-hsigma of the alkyl group, and then disperse the charge of the carbocation and make it stable. Therefore, the more alkyl groups are linked, the more stable they are, i.e., tertiary carbocation, secondary carboxacation, primary carbocation, and methyl group.

2.If the attached halogen, taking Cl as an example, the electronegativity of Cl is greater than C, there is an induction of electron sucking, and at the same time it is 2S2 2Px2 Spy2 2Pz, that is, there are unpaired electrons, there are carbocations that are sp2 hybridized, there are empty P orbitals, and Cl unpaired electrons can go to empty orbitals, and the positive charge can be dispersed, and the total effect is to make carbocations more unstable.

3. If it is an allyl type and benzyl carbocation, due to the p-pai conjugation, the charge can be dispersed, and the carbocation is more stable.

This question is the first case, so d is the most stable, and the carbocation in d is directly linked to the alkyl group.

Stability of metal carbonates, the higher the charge of metal ions, the smaller the radius, and the more unstable.

For example, calcium carbonate.

The decomposition temperature is 900 mg, magnesium carbonate.

The temperature of decomposition is 402. Calcium ions.

The radius of the magnesium ion is 100pm, the radius of the magnesium ion is 72pm, because the radius of the magnesium ion is small, the polarization of the denier bridge root of the carbonate is much stronger than the calcium ion, so the decomposition chain of magnesium carbonate is much lower than that of calcium carbonate. Similarly, the higher the charge, the stronger the polarization ability of the carbonate and the lower the decomposition temperature.

The more groups around the carbocation, the more stable the carbocation. The more dispersed the charge, the smaller the positive charge on the positive carbon ion, and the more stable the ion is.

The carbon of the carbocation is sp2 hybridized, and its p orbital is empty, and it is relatively electron-deficient and unstable, so it is more stable when attached to the electron-donor group.

The structure and stability of carbocations are directly affected by the groups to which they are attached. The general law of their stability is as follows:

1) Benzyl type or allyl type is generally more stable;

2) Other carbocations are: 3°>2°>1°;

The stability of different carbocations can be explained by superconjugation).

The more stable the carbocation, the lower the energy and the easier it is to form. Carbocations can be divided into classical carbocations and non-classical carbocations according to their different structural characteristics.

If there are more electron groups around, it will be stable, and if there are more electron-withdrawing groups, the carbon will be unstable.

The easier the charge is dispersed, the more stable it is:

The more resonances are drawn after the carbocation is present, and the more stable the resonance is the more stable.

The more substituents (with hydrogen) of carbon are, the more stable it is, and the more stable it is when there are electron-donor groups around it.

Depending on the characteristics of your problem, the analysis is as follows:

The stability of carbocation is generally allyl and benzyl.

Class > tertiary carbon》 secondary carbon > primary carbon.

When there is a common effect, it can strengthen its stability!

Electron-withdrawing groups.

Make the electronic cloud.

Deviating from the positive carbon ion is not conducive to dispersing the positive charge!

1 A > b > c The stability of carbocations is generally allyl and benzyl > tertiary carbon and secondary carbon > primary carbon.

2 a>b > c can strengthen its stability when it is used as a common solution! Ethyl has a stronger ability to donate electrons than methyl groups and has a greater ability to disperse positive charges.

3 b >a > c are allyl " tertiary carbon " sleek primary carbon .

4 a > b > c tertiary carbon》 Secondary carbon > primary carbon, and the weaker the attached electron-withdrawing group, the more stable the orange simple wax.

Depending on the characteristics of your problem, the analysis is as follows:

The stability of carbocation is generally allyl, benzyl >tertiary carbon, secondary carbon > primary carbon, which can strengthen its stability!

The electron-withdrawing group causes the electron cloud to deviate from the positive carbon ions, which is not conducive to the dispersion of the positive charge!

1 A > b > c The stability of carbocations is generally allyl and benzyl > tertiary carbon and secondary carbon > primary carbon.

2 a>b > c can strengthen its stability when they work together! Ethyl has a stronger ability to donate electrons than methyl groups and has a greater ability to disperse positive charges.

3 b >a > c are allyl group》 tertiary carbon》 primary carbon4 a > b > c tertiary carbon》 secondary carbon > primary carbon, and the weaker the attached electron withdrawing group, the more stable it is.

1) The more substitutions, the more stable they are, so a>b>c

2) B has two identical resonance formulas, and A's resonance formula is C, both of which are not as stable as B, so B > A>C

3) The allyl group should be larger than the general group, so b>a>c

4) There is an electron-withdrawing group, and the stronger the electron-withdrawing ability, the more unstable it is, so a>b>c

Isn't b in 2 allyl how can it be more stable than a.

b>a≈d>c

b is the benzyl position, and there is an electron-donating effect of another isopropyl group, which is the most stable.

c is a cyclic ion and is the most unstable.

The stability of the allyl and benzyl sites is about the same.