Reactive Intermediates
In chemistry, reactive intermediates are termed as short-lived, highly reactive atoms with high energy. They rapidly transform into stable particles during a chemical reaction. In specific cases, by means of matrix isolation and at low-temperature reactive intermediates can be isolated.
Hydride Shift
A hydride shift is a rearrangement of a hydrogen atom in a carbocation that occurs to make the molecule more stable. In organic chemistry, rearrangement of the carbocation is very easily seen. This rearrangement can be because of the movement of a carbocation to attain stability in the compound. Such structural reorganization movement is called a shift within molecules. After the shifting of carbocation over the different carbon then they form structural isomers of the previous existing molecule.
Vinylic Carbocation
A carbocation where the positive charge is on the alkene carbon is known as the vinyl carbocation or vinyl cation. The empirical formula for vinyl cation is C2H3+. In the vinyl carbocation, the positive charge is on the carbon atom with the double bond therefore it is sp hybridized. It is known to be a part of various reactions, for example, electrophilic addition of alkynes and solvolysis as well. It plays the role of a reactive intermediate in these reactions.
Cycloheptatrienyl Cation
It is an aromatic carbocation having a general formula, [C7 H7]+. It is also known as the aromatic tropylium ion. Its name is derived from the molecule tropine, which is a seven membered carbon atom ring. Cycloheptatriene or tropylidene was first synthesized from tropine.
Stability of Vinyl Carbocation
Carbocations are positively charged carbon atoms. It is also known as a carbonium ion.
![Draw curved arrows to show the movement of electrons in this step of the mechanism.
Arrow-pushing Instructions
:O:
:
H3C
CH3
H3C
CH3
Submit Answer
Retry Entire Group
9 more group attempts remaining](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F6e53cf2c-4bf5-4ccd-bd0e-fb990a97eda5%2Fc7d9e0ad-7f29-4b1c-b580-8f4fd7aec5b7%2F1qd0q4r_processed.jpeg&w=3840&q=75)
![OH
NaOH
H3C
CH3
H3C
CH3
Alkyl halides undergo nucleophilic substitution and elimination reactions. When the kinetics of the reaction are
measured, if the rate of the reaction is found to be dependent only upon the concentration of the alkyl halide the
reaction is first order. The substitution reaction is thus termed Sy1, and the elimination reaction is termed E1. These
reactions are unimolecular and occur in two steps. The first step is rate-limiting and involves the loss of the leaving
group to form a carbocation. In the second, fast, step the nucleophile adds to the carbocation in the SN1 reaction or
elimination occurs to give an alkene in the E1 reaction. Because the carbocation is planar, the nucleophile can add to
either face and therefore racemization is usually observed although solvent effects can influence this somewhat. E1
elimination follows Zaitsev's rule and typically yields the most substituted alkene as the major product.
Conditions which favor the Sy1/E1 pathway include the use of a weak nucleophile and a polar protic solvent. The same
reaction conditions apply for both S1 and E1, therefore these reactions will compete. It is usually difficult to predict
which pathway, substitution or elimination, will predominate and so a mixture of products is frequently observed.
In contrast to the El reaction which involves a carbocation intermediate, the E1CB reaction takes place through a
carbanion intermediate. Base-induced abstraction of a proton in a slow, rate-limiting step gives an anion which then
expels the leaving group from the adjacent carbon. The reaction is particularly suited to the elimination of substrates
which contain poor leaving groups two całbons removed from a carbonyl group. The poor leaving group disfavors the
alternative E1 and E2 reactions, and the carbonyl group helps to stabilize the anion via resonance.
Draw curved arrows to show the movement of electrons in this step of the mechanism.
Arrow-pushing Instructions
:ÖH :0:
:ö:
:0:
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