When tricyclic cyclooctyne derivative A reacts with benzyl azide (CeHsCH2N3), a [3+2] cycloaddition occurs between the alkyne and the azide (called a click reaction) to install a new five-membered heterocycle. N=N=N Ph Ph- „N +C A B (a) Propose a plausible mechanism for the formation of B. (b) Compounds B and C are constitutional isomers that are formed in roughly equal amounts. Draw the structure of compound C.
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.
having issues with the mechanisms (org chem)
![**Title: Cycloaddition Reaction and Isomer Formation**
---
### Cycloaddition Reaction
When tricyclic cyclooctyne derivative A reacts with benzyl azide (C₆H₅CH₂N₃), a [3+2] cycloaddition occurs between the alkyne and the azide (called a click reaction) to install a new five-membered heterocycle.
**Chemical Reaction Overview:**
**Reactant A:**
```
/\/\
|O O|
/ \ N C₆H₅-CH₂-N₃
|| ||
\ /
|N N|
\/\/
/\/\
/ \
```
**Reactant Benzyl Azide:**
```
Ph
|
N³⁻
```
**Products:**
```
Product B:
/\/\
|O |
/ \ + Compound C
|N N|
\/\/ (not displayed)
/\/\
|
BENZYL
```
### Mechanism Proposal for Formation of B
(a) Propose a plausible mechanism for the formation of B.
Note: Students are encouraged to draw out the step-by-step reaction mechanism, focusing on the movement of electron pairs and inter-conversion between intermediates leading up to the final product B.
### Isomer Formation
(b) Compounds B and C are constitutional isomers that are formed in roughly equal amounts. Draw the structure of compound C.
---
### Descriptive Diagram Explanation
**Diagram Content:**
1. **Reactant A (Tricyclic cyclooctyne derivative):**
- Structured with a three-ring system with a nitrogen and oxygen atoms, indicating an intricate cyclic structure.
2. **Benzyl Azide (C₆H₅CH₂N₃):**
- Represented with a phenyl group attached to a chain containing an azide group (N₃).
3. **Product B:**
- Resultant compound featuring a five-membered heterocyclic ring containing two nitrogen atoms, indicating the occurrence of the click reaction.
4. **Product C:**
- Not displayed in the diagram but implied to be a structural isomer of B.
### Instructions for Students
- **Mechanism:**
Students are prompted to draft a](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F206206aa-1104-4dbc-9e08-21639f631eee%2Fbeb24430-1b94-463d-ac9c-fce92dd6f2b1%2F0xnnejr_processed.png&w=3840&q=75)
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