Tertiary carbocations are more stable than secondary ones due to an effect known as hyperconjugation. A neighboring C-H bond can donate some of its electron density into the vacant p-orbital of a carbocation thus making it more stable. Carbon isn't very electronegative and readily donates electron density.
If the internal energy of the radical is high, the radical is unstable. It will try to reach a lower energy level. If the internal energy of the radical is low, the radical is stable. It will have little tendency to react further.
Since, C˙H3 has no hyperconjugative structure, so it is least stable.
In CH3˙CHCH3,˙C6H5 the radical cannot undergo resonance . But in C6H5˙CHCH3, the radical can undergo resonance with the benzyl ring. So it will be the most stable free radical .
What can be said is that due to resonance, both the allylic and benzylic radicals are more stable than the t-butyl or ethyl radicals which are not resonance stabilized. For the benzyl radical you can draw even more resonance structures.
Carbocations Are Stabilized By Neighboring Carbon-Carbon Multiple Bonds. Carbocations adjacent to another carbon-carbon double or triple bond have special stability because overlap between the empty p orbital of the carbocation with the p orbitals of the π bond allows for charge to be shared between multiple atoms.
In case of alkanes, free radicals stabilised with increase in substitution of methyl groups, in other words, if we take an example of methyl, ethyl, and any other methyl substituted hydrocarbon like which is a secondary radical, then the secondary radical will be most stable, followed by the ethyl and then methyl will
Free radicals have only 7 electrons in their valence shell. Carbocations are also electron-deficient species. Since carbocations have only 6 valence electrons, they are higher in energy than free radicals. We know this, because many carbocations rearrange to become more stable.
First, it is true that tertiary carbocations are generally more stable than primary carbocations (and secondary carbocations) due to having more inductively donating alkyl groups. The hyperconjugative effect can also be invoked to explain the relative stabilities of primary, secondary, and tertiary carbocations.
Benzylic carbocations are so stable because they have not one, not two, but a total of 4 resonance structures. As you increase substitution, the benzylic carbocation becomes more and more stable. The most stable version is the tertiary benzylic carbocation.
Stability order of carbanions decreases as we move from primary to tertiary anion because due to +I effect of methyl groups there is an increased intensity of negative charge on central carbon of tertiary carbanion which further makes it unstable.
You will see that the electron pushing effect of the CH3 group is placing more and more negative charge on the positive carbon as you go from primary to secondary to tertiary carbocations. The more you can spread the charge around, the more stable the ion becomes.
Tertiary C-H bonds are weaker than primary or secondary, so they are easier to break.
Tertiary alcohols are more stable because of the three alkyl groups. First of all, the three alkyl groups prevent the tertiary alcohol from being oxidised because there's no hydrogen bonded to the carbon atom with hydroxyl group, which means that no hydrogen will be lost from the alcohol.
Tertiary haloakanes react via an sN1 mechanism that has a much lower activation energy than the sN2 mechanism with the high energy transition state. Hence tertiary haloalkanes react faster then secondary, which in turn react faster than primary.
As a result, benzylic and allylic carbocations (where the positively charged carbon is conjugated to one or more non-aromatic double bonds) are significantly more stable than even tertiary alkyl carbocations.
Answer. because -CH3 is electron providing group. and more the number of electron providing group more stable will be carbocation. Tertiary carbocation possess minimum positive charge due to - (1) hyper conjugation (2) electron releasing inductive effect of alkyl group .
The data is that benzyl cation [PhCH2]+ is indeed more stable than allyl cation [CH2CHCH2]+ when one measures the gas phase hydride ion affinities in kcal/mol. Benzyl cation is 234 kcal/mol and allyl cation is 256 kcal/mol, so benzyl cation is more “stable” by 22 kcal/mol - that's a lot of kcal/mol!
Yes carbocation is more stable. let's take for example the ter-butyl carbocation (Ch3)3-C+ this charged ion is highly stabilized due to the presence of the three donor methly groups that donate electrons, and hence largely stabilize the positive charge.
Option D trimethyl methane is least stable because the methyl groups which are attached are also very unstable making the carbanion least stable.
