Why are tertiary carbocations more stable than secondary and primary carbocations? ?
An understanding of Carbocation formation is vital for determining if the reaction is by an SN1 or SN2 pathway. SN1 Reactions have a carbocation intermediary, and by knowing if a carbocation is formed, you know the reaction pathway and mechanism. Also, by understanding which cations are favoured, you are better able to predict the pathway a reaction will follow. Tertiary carbocations are more stable than both primary and secondary carbocations, as the delocalised charge (+ve on the Carbon) is stabilised by the heavier groups. It's kind of hard to demonstrate without a diagram handy, but basically as a primary carbocation is a positive carbon centre with three H groups, (or two H's one R group) the H groups do not stabilise the charge very much, making the molecule much more unstable. Whereas the tertiary has three methyl groups stabilising the charge which makes the cation more solid. The process here is known as hyperconjugation, the process in which the pi orbitals interact to give added stability to the complex. I don't know how much detail you need to go into, but if you need to know more, google hyperconjugation.
In carbocation, which is more stable, primary, secondary, or tertiary?
Tertiary carbocation is more stable.Carbocation is electron deficient. And alkyl groups are electron donating. More the number of alkyl groups attached to carbocation, higher is the stability.The stability of tertiary carbocation can be explained with the help of inductive effect and hyperconjugation.
Why are tertiary carbocations more stable than other carbocations?
Tertiary carbocations are more stable than primary or secondary carbocations because they have three methyl groups to distribute it's positive charge rather than only one or two methyl groups. Each methyl group has three hydrogens to help spread out the positive charge, which is more effective than just having a hydrogen in its place. Of course, the more the positive charge is spread out, the more stable your carbocation will be! Also, since hydrogen is less electronegative than carbon, the methyl groups will have 3 permanent dipoles from its three hydrogens that cause a stronger dipole to point towards the centre carbon than simply one hydrogen in its place.Credits to my first year Chem Prof for this answer.
If tertiary carbocations are very stable then why are they more reactive than secondary or primary carbocations?
3 degree carbocations are more stable than 1&2 degrees. We all know why, in short it's bcz of electron releasing of attached alkyl groups… Well, there is no reason to think the 3 degree carbonation is more reactive or not… you should know all carbocations/ carbenium ions are rxn. intermediates. Ok, let me explain by taking an example, say in SN1 rxn.,the 1st step which is the rds ,is the formation of carbocation….now greater the stability of carbenium ion(lower will be Ea value), greater will be the rate of that corresponding SN1 rxn [why Ea of the RDS become lower, can be made out using Hammond Postulate — if u know this postulate, u can certainly understand, in SN1 rxn, the structure of T.S. is closer to carbocation which produced as intermediate, than the starting material bcz the energy gap between substrate and T.S.Is a much more higher than that between intermediate and T.S in SN1 rxn — one can easily makeout from energy profile ].So not the reactivity that matters, but the stability of carbenium ion . And yes, rate will be as follows 1<2<3 carbocation (increasing manner)—simply it doesn't indicate their reactivity… Don't mess it up .
Why are primary and secondary carbons less stable than tertiary carbons?
Regarding the stabilities of free radicals, the "energy required to break the C-H bond is at the greatest for a methyl carbon, and it decreases for a secondary carbon, and tertiary carbon. The more highly substituted the carbon atom, the less energy is required to form the free control. It is conclude that free radicals are more stable if they are more highly substituted." This makes forming a secondary or tertiary carbon easier than a methyl corbon. It is true that the energy of a C-H primary bond has the highest value, but this tells you only that, if compared to other carbons, it's much more difficult to transform a primary C into a radical, while the process is easier for secondary and tertiary carbons. A high bond energy means a low potential energy and this tells us that a free CH³ radical will quickly take an hydrogen atom from another compound to reach its favored energetic state. The same thing happens with secondary and tertiary carbons, but these, if compared with primary carbons, are less likely to return to their original states (to reach a greater stability) as they don't have the same stability as CH⁴(and their bonds aren't that strong).If you want to take a deeper peek into this topic try to google "Hyperconjugation.”Thank you.
Which carbocation is more stable : Benzyl or Tertiary?
Great this is one question where you have two different answers. Let me explain both of them.Most of us believe benzyl carbocation is more stable than tertiary because benzyl carbocation involves in resonance.Some of the authors believe that Tertiary carbocation is more stable as it involves maximum +I effect and maximum hyperconjuation +H (9 alpha hydrogens). Maximum +I and +H is more dominant than +M effect. Thus tertiary carbocation is more stable than benzyl carbocation.So i suggest you to go for the answer according to the options provided , if one of the option you find benzyl is more than tertiary you can go for it else if it is given benzyl is more stable than tertiary then you go for it.If both the options are there then the best one will be tertiary carbocation is more stable than benzyl.
Is the tertiary carbocation with 3 ethyl groups more stable than tertiary butyl carbocation?
A tertiary carbocation is stabilized by the inductive effect of the bond formed with the neighboring carbons, and because an ethyl group and a methyl group are both extremely similar, it is unlikely that the slightly longer ethyl group would improve the inductive effect by any significant amount. However, I have limited knowledge on what might happen if this chain length was extended considerably, perhaps there is some orientation in 3-D space that would have some effect that provides additional stability.