Consider the following reaction: AICH Toluene MECOCI Me- COME UCI How are these products being formed? Show all appropriate steps (mechanism) in this reaction. Show all appropriate arrows!!!
Basics in Organic Reactions Mechanisms
In organic chemistry, the mechanism of an organic reaction is defined as a complete step-by-step explanation of how a reaction of organic compounds happens. A completely detailed mechanism would relate the first structure of the reactants with the last structure of the products and would represent changes in structure and energy all through the reaction step.
Heterolytic Bond Breaking
Heterolytic bond breaking is also known as heterolysis or heterolytic fission or ionic fission. It is defined as breaking of a covalent bond between two different atoms in which one atom gains both of the shared pair of electrons. The atom that gains both electrons is more electronegative than the other atom in covalent bond. The energy needed for heterolytic fission is called as heterolytic bond dissociation energy.
Polar Aprotic Solvent
Solvents that are chemically polar in nature and are not capable of hydrogen bonding (implying that a hydrogen atom directly linked with an electronegative atom is not found) are referred to as polar aprotic solvents. Some commonly used polar aprotic solvents are acetone, DMF, acetonitrile, DMSO, etc.
Oxygen Nucleophiles
Oxygen being an electron rich species with a lone pair electron, can act as a good nucleophile. Typically, oxygen nucleophiles can be found in these compounds- water, hydroxides and alcohols.
Carbon Nucleophiles
We are aware that carbon belongs to group IV and hence does not possess any lone pair of electrons. Implying that neutral carbon is not a nucleophile then how is carbon going to be nucleophilic? The answer to this is that when a carbon atom is attached to a metal (can be seen in the case of organometallic compounds), the metal atom develops a partial positive charge and carbon develops a partial negative charge, hence making carbon nucleophilic.
![### Detailed Mechanism of Friedel-Crafts Acylation Reaction
**Consider the following reaction:**
\[ \text{Toluene} + \text{MeCOCl} \xrightarrow{AlCl_3} \text{Me} - \underset{\text{Acyl group}}{\overset{\text{Acylated toluene}}{\text{COMe}}} + \text{HCl} \]
**Question:**
How are these products being formed? Show all appropriate steps (mechanism) in this reaction. **Show all appropriate arrows!!!**
### Explanation:
This reaction is a Friedel-Crafts acylation, an important method in organic chemistry for introducing an acyl group into an aromatic ring. The following steps outline the detailed mechanism:
1. **Formation of the Acylium Ion:**
- The acyl chloride (MeCOCl, where Me = CH₃) reacts with aluminum chloride (AlCl₃), a Lewis acid. This interaction polarizes the carbonyl group (C=O), leading to the formation of the acylium ion (MeCO⁺) and an AlCl₄⁻ ion.
\[
\text{MeCOCl} + \text{AlCl}_3 \rightarrow \text{MeC}^+O + \text{AlCl}_4^-
\]
2. **Generation of the Electrophile:**
- The acylium ion (MeCO⁺), generated in the previous step, serves as the electrophile that will attack the aromatic ring in toluene.
3. **Electrophilic Attack on Toluene:**
- Toluene, an aromatic compound, acts as a nucleophile due to the delocalized π-electrons in the benzene ring. The acylium ion attacks the aromatic ring, creating a sigma complex (arenium ion).
\[
\chemfig{*6(=-(*5(=-([-H]-Me)-=))-=)}
\rightarrow \chemfig{*6(-*5(-=(-(CO-Me)-\chemfig{AlCl_3})))}
\]
4. **Restoration of Aromaticity:**
- In the final step, the proton (H⁺) that was initially attached to the carbon atom at the site of electrophilic attack is removed. This](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F650638ef-17d9-4755-bd2c-89f9558934a8%2Fdffdf354-4f78-43f4-84b9-ded4def46a46%2Fd7c3bzn_processed.jpeg&w=3840&q=75)
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