To preview image click here Br A B C Br Br NaOH HMPA NaOH HMPA NaOH HMPA 1. Decide which of these three SN2 reactions would be fastest [ Select] 2. Decide which of these three SN2 reactions would be slowest [Select] 3. Is the solvent polar protic or polar aprotic [Select] [Select] polar protic polar aprotic 4. Which reaction will have a smaller activati [Select] OH OH II. LOH
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.
![**SN2 Reaction Analysis**
In this educational module, we explore three SN2 reactions involving the substitution of a bromine (Br) atom with a hydroxide (OH) group using sodium hydroxide (NaOH) in the presence of hexamethylphosphoramide (HMPA).
**Reactions:**
- **Reaction A:**
- Starting Material: A chiral compound with Br.
- Product: The chiral compound with OH.
- **Reaction B:**
- Starting Material: A linear cyclic compound with Br.
- Product: The corresponding cyclic compound with OH.
- **Reaction C:**
- Starting Material: A linear chain compound with Br.
- Product: The linear chain compound with OH.
**Key Questions:**
1. **Decide which of these three SN2 reactions would be fastest:**
- [Select]
2. **Decide which of these three SN2 reactions would be slowest:**
- [Select]
3. **Is the solvent polar protic or polar aprotic?**
- Options:
- Polar protic
- Polar aprotic
4. **Which reaction will have a smaller activation energy?**
- [Select]
**Notes:**
- **HMPA** is a polar aprotic solvent, which facilitates SN2 reactions by stabilizing the transition state without solvating the nucleophile too strongly, thus enhancing reaction rates.
- **Reaction Rates** are influenced by the structure of the starting material. SN2 reactions are generally faster with less steric hindrance.
Explore the concepts and mechanisms to determine the answers based on the provided data.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4fc28238-d87d-4137-810c-cbaeffa57236%2F2dc0f037-ee6e-4472-85cf-bbfe04c8e76d%2Fu5vaxn_processed.jpeg&w=3840&q=75)
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