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.
![### Major Organic Products of Reactions
#### Reaction (a):
Chemical equation:
- Reactant: Two carbonyl compounds in a ring structure, specifically a β-keto ester.
- Reagents:
1. 1,3-Propanediol (HO-CH2-CH2-CH2-OH)
2. Grignard reagent (CH3MgBr)
3. Acidic workup (H3O+) with heat (Δ)
**Explanation:**
1. The diol acts as a protecting group or reducing agent.
2. The Grignard reagent attacks the carbonyl carbon, forming a new carbon-carbon bond.
3. Acidic hydrolysis removes protecting groups, forming alcohols or additional carbonyl compounds.
**Expected Product:**
The primary reaction product will likely be a tertiary alcohol, resulting from the addition of a methyl group (from CH3MgBr) to one of the carbonyl structures.
---
#### Reaction (f):
Chemical equation:
- Reactant: Cyclohexanone.
- Reagent: Ethylamine (NH-CH2-CH3).
**Explanation:**
1. The nitrogen of the ethylamine attacks the carbonyl carbon of cyclohexanone.
2. An imine is formed through condensation (removal of water).
**Expected Product:**
The primary product will be an imine, resulting from the nucleophilic addition of the amine to the ketone.
---
#### Reaction (x):
Chemical equation:
- Reactant: A dimethyl-substituted benzene (specifically, meta-xylene).
- Reagents:
1. Bromination in presence of FeBr3 (Br2, FeBr3)
2. Grignard formation (Mg, Et2O)
3. Reaction with an epoxide
4. Acidic workup (H3O+)
**Explanation:**
1. Bromination adds a bromine atom to the benzene ring.
2. Magnesium forms a Grignard reagent with the brominated compound.
3. The Grignard reagent opens the epoxide ring, forming a new alcohol with two additional carbon atoms.
4. Acidic hydrolysis ensures the stability of the alcohol.
**Expected Product:**
The primary product will be a secondary or tertiary alcohol derived from the addition of the Grignard reagent to the epoxide, expanding the carbon chain attached to the benz](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fd32995d5-5fea-4926-a0bc-dd690042cbac%2F4afc3daa-62b8-4fe0-bc5f-6e38ecec9f6a%2Fo3bd17j_processed.png&w=3840&q=75)
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