4. Nitromethane (CH3NO₂) has a pką value of 10. Does this mean that the nitro group (NO₂) is an electron withdrawing group or an electron donating group? Explain. :O: "Le N H H pka 10 H
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.
![### Question 4: Understanding the Electronic Effects of the Nitro Group in Nitromethane
**Problem Statement:**
Nitromethane (CH₃NO₂) has a \( pK_a \) value of 10. Does this mean that the nitro group (NO₂) is an electron withdrawing group or an electron donating group? Explain.
**Diagram:**
The provided diagram illustrates the molecular structure of nitromethane (CH₃NO₂). The nitro group (NO₂) is attached to the central carbon atom, which is further bonded to three hydrogen atoms (H). The nitro group consists of nitrogen (N) double-bonded to one oxygen atom (O) and single-bonded to another oxygen atom that carries a negative charge. The nitrogen itself has a positive charge.
The molecular structure is depicted as follows:
```
:O:
..
\..
\..
⊖
O
||
||
N
//
//
⊕
N
/
/
C
(-H -H -H)
```
Additionally, the \( pK_a \) value of nitromethane is indicated as 10.
**Explanation:**
The \( pK_a \) value is a measure of the acidity of a compound. A \( pK_a \) value of 10 indicates that nitromethane is relatively acidic. The acidity of a compound is influenced by the electronic effects of its substituent groups.
- **Electron Withdrawing Group (EWG):** These groups attract electrons towards themselves through inductive or resonance effects, making the compound more acidic. This is because the withdrawal of electrons stabilizes the negative charge on the conjugate base after deprotonation.
- **Electron Donating Group (EDG):** These groups donate electrons away from themselves, making the compound less acidic by destabilizing the conjugate base after deprotonation.
Given that nitromethane (CH₃NO₂) has a relatively low \( pK_a \) (meaning it is quite acidic), the nitro group (NO₂) must be functioning as an electron withdrawing group. The electron withdrawal by the NO₂ group stabilizes the negative charge on the conjugate base of nitromethane, thereby enhancing its acidity.
In conclusion, the \( pK_a \) value of 10 for nitrom](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F5e0b02f6-f1e5-40a9-9b9d-2488529fd6df%2F3fe681f5-e9f8-47fc-a40c-9ee9a27fcfe1%2Fuxvjish_processed.png&w=3840&q=75)
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