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.
What, if anything, would be different about the product of the reaction if you started with Z-stilbene instead of E-stilbene?
![### Scheme 1: Overall Bromination Reaction
The first reaction starts with E-stilbene, which is converted into (1R,2S)-1,2-dibromo-1,2-diphenylethane using pyridinium tribromide in the presence of acetic acid at 50°C. The chemical reaction equation is:
- **Reactant:** E-stilbene
- **Reagent:** Pyridinium tribromide, Acetic acid, 50°C
- **Product:** (1R,2S)-1,2-dibromo-1,2-diphenylethane
### Scheme 2: Decomposition of Pyridinium Bromide
This scheme illustrates the decomposition process of pyridinium bromide upon heating. Pyridinium tribromide decomposes to produce pyridine, hydrogen bromide (HBr), and bromine (Br₂).
- **Reactant:** Pyridinium bromide
- **Products:** Pyridine, HBr, Br₂
### Scheme 3: Synthesis of Diphenylacetylene
The third scheme demonstrates the conversion of (1R,2S)-1,2-dibromo-1,2-diphenylethane into diphenylacetylene. This transformation uses potassium hydroxide (KOH) in ethanol under microwave conditions.
- **Reactant:** (1R,2S)-1,2-dibromo-1,2-diphenylethane
- **Reagents:** KOH (2 equivalents), EtOH, Microwave
- **Products:** Diphenylacetylene, H₂O, KBr
The reaction details depict a typical method of organic synthesis involving bromination and subsequent elimination to form an acetylene compound.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc47c8b08-049c-42f2-9d94-570c13eff388%2F174eace1-98d9-4b51-beb2-ac9a4bca5782%2Fkor07lw_processed.png&w=3840&q=75)
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