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.
![### Bromination of Ethylbenzene
**Reaction Overview:**
The following reaction proposes the bromination of ethylbenzene using bromine (Br₂) in the presence of ferric bromide (FeBr₃) as a catalyst.
**Reaction Equation:**
\[ \text{C}_6\text{H}_5\text{CH}_2\text{CH}_3 + \text{Br}_2 \xrightarrow{\text{FeBr}_3} \]
**Products:**
Three possible ortho, meta, and para brominated ethylbenzene products are depicted:
1. **Product I: Ortho-Bromotoluene**
- Structural Formula: A benzene ring with an ethyl group (–CH₂–CH₃) and a bromine (–Br) atom at adjacent positions (ortho).
2. **Product II: Meta-Bromotoluene**
- Structural Formula: A benzene ring with an ethyl group (–CH₂–CH₃) and a bromine (–Br) atom separated by one carbon atom (meta).
3. **Product III: Para-Bromotoluene**
- Structural Formula: A benzene ring with an ethyl group (–CH₂–CH₃) and a bromine (–Br) atom opposite each other (para).
**Diagram Description:**
The illustrated diagram begins with ethylbenzene reacting with bromine (Br₂) under the catalytic influence of FeBr₃. This results in three possible brominated products, each differing by the position of the bromine on the benzene ring:
- Ortho position: where bromine is adjacent to the ethyl group.
- Meta position: where bromine is one carbon away from the ethyl group.
- Para position: where bromine is opposite to the ethyl group.
**Mechanism Insight:**
The orientation of the substituents (ethyl group) on the benzene ring directly affects the site of bromination due to the electron-donating effect, directing the bromination to the ortho and para positions predominantly, though not exclusively.
**Educational Importance:**
Understanding the bromination of ethylbenzene is crucial for learning about electrophilic aromatic substitution reactions and the influence of substituents on the reactivity and orientation of the aromatic ring. This knowledge underpins more complex organic synthesis reactions and applications in materials and pharmaceuticals.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F6da61eaa-bdf5-4117-bcfb-23e14b5928a8%2F1bedfbe8-7876-40e5-ad3b-ed7bebec6057%2Fklj6j5j_processed.jpeg&w=3840&q=75)
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