. Fill in the mechanism below with curved-arrow electron pushing as well as necessary lone pairs of electrons and all formal charges. Note: Some atoms are only shown when relevant. b. Circle the rate determining step of the reaction.
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.
a. Fill in the mechanism below with curved-arrow electron pushing as well as necessary lone pairs of electrons and all formal charges. Note: Some atoms are only shown when relevant.
b. Circle the rate determining step of the reaction.
![### Mechanism of Alcohol Conversion to Alkyl Chloride using Hydrochloric Acid
The image outlines the detailed step-by-step mechanism of converting an alcohol group to an alkyl chloride using hydrochloric acid (HCl). The chemical reaction progresses through several stages, incorporating the protonation of the alcohol group and subsequent substitution of the water molecule with a chloride ion (Cl-).
#### Step-by-Step Mechanism:
1. **Protonation of Alcohol:**
- Initially, the alcohol (ROH) is protonated by hydrochloric acid (HCl), resulting in the formation of an oxonium ion (ROH2+).
\[
\text{Alcohol (\(ROH\))} + HCl \rightarrow \text{Protonated Alcohol (\(ROH_2^+\))}
\]
2. **Formation of Carbocation Intermediate:**
- The protonated alcohol (ROH2+) loses a water molecule (H2O) to form a carbocation (R+). This is indicated by the departure of the water molecule.
\[
\text{Protonated Alcohol (\(ROH_2^+\))} \rightarrow \text{Carbocation (\(R^+\))} + H_2O
\]
3. **Nucleophilic Attack by Chloride Ion:**
- The chloride ion (Cl-) then attacks the carbocation, leading to the formation of alkyl chloride (RCl).
\[
\text{Carbocation (\(R^+\))} + Cl^- \rightarrow \text{Alkyl Chloride (\(RCl\))}
\]
### Detailed Example:
The diagram illustrates specific molecular structures undergoing the described transformation. The initial reactant, an alcohol, is progressively converted into an alkyl chloride.
1. **Starting Alcohol:**
The reactant is a simple alcohol, depicted with its hydroxyl group (OH).
2. **Protonation:**
Upon treatment with hydrochloric acid, the hydroxyl group is protonated, forming an oxonium ion (indicated by a positively charged oxygen attached to two hydrogens).
3. **Formation of Carbocation:**
The intermediate oxonium ion releases a water molecule, resulting in a positively charged carbon structure or carbocation.
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