What is a Nucleophile?
A nucleophile is an affluent electron species that gives electron pairs to an electron-deficient species to form a new covalent bond.
Examples: Halides ( Fluoride, Chloride, Bromide, Iodide), Hydroxide, Cyanide, Ammonia, and Water are examples of Nucleophiles.
What is a Base?
A base is an affluent electron species that gives electron pairs to a hydrogen atom to form a new covalent bond.
Examples: Halides ( Fluoride, Chloride, Bromide, Iodide), Hydroxide, Cyanide, Ammonia, and Water are examples of the base.
- All nucleophiles are bases, or all bases are nucleophiles. Depending on the specie, an electron-rich species is donating its electrons.
Table of Content
Good Nucleophiles
A nucleophile is an affluent electron species that gives electron pairs to an electron-deficient species to form a new covalent bond.
Examples: Halides ( Fluoride, Chloride, Bromide, Iodide), Hydroxide, Cyanide, Ammonia, and Water are examples of Nucleophiles.
- All nucleophiles are bases. Depending on the species, the nucleophile is donating its electrons.
- A good nucleophile donates its electrons quickly to an electron-deficient species to form a covalent bond. In contrast, a poor nucleophile donates its electrons slowly to an electron-deficient species.
We can distinguish between good and poor nucleophiles by measuring the reaction rate.
Good Bases
A base is an affluent electron species that gives electron pairs to a hydrogen atom to form a new covalent bond.
Examples: Halides ( Fluoride, Chloride, Bromide, Iodide), Hydroxide, Cyanide, Ammonia, and Water are examples of bases.
- All bases are nucleophiles. Depending on specie, the base is donating its electrons.
- A good base donates its electrons quickly to a hydrogen atom to form a covalent bond. In contrast, a poor base donates its electrons slowly to a hydrogen atom.
We can distinguish between good and poor bases by measuring the pKb value.
Good Nucleophiles vs Good Bases
Good Nucleophiles / Good Bases
A good nucleophile is generally a good base. Examples: Alkoxide ion (OR– ), Hydroxide ion (OH– ) and Azanide ion (NH2– ).
Good Nucleophiles / Poor Bases
A good nucleophile can be a poor base. Example: Iodide (I– ) is a good nucleophile but a poor base. The large electron cloud of Iodide (I– ) is highly polarisable, making it a poor base.
Poor Nucleophiles / Good Bases
A poor nucleophile can be a good base. Examples: LiN[CH(CH₃)₂], t-BuO⁻, and t-BuLi are good bases but poor nucleophiles because of steric hindrance.
Poor Nucleophiles / Poor Bases
A poor nucleophile can be a poor base. Examples: Water ( H2O), Alcohol (ROH), and Carboxylic Acid (RCOOH).
Difference between Nucleophile and Base
| S No. | Nucleophile | Base |
|---|---|---|
| 1. | A nucleophile is an affluent electron species that gives electron pairs to an electron-deficient species to form a new covalent bond. | A base is an affluent electron species that gives electron pairs to a hydrogen atom to form a new covalent bond. |
| 2. | Nucleophiles are influenced by reaction rate and electronic wavelengths. | Bases are influenced by heat and thermodynamics. |
| 3. | Nucleophiles are attracted to electron-deficient carbon atoms. | Bases are attracted to hydrogen atoms. |
| 4. | Nucleophiles favour electrophilic reactions based on electron transfer. | Bases favour neutralisation reaction. |
| 5. | Nucleophiles favour substitution reaction. | Bases favour elimination reaction. |
| 6. | Nucleophiles are an excellent chemical mediator. | Bases are an inferior chemical mediator. |
Frequently Asked Questions on Good Nucleophiles vs Good Bases
What is a nucleophile?
A nucleophile is an affluent electron species that gives electron pairs to an electron-deficient species to form a new covalent bond.
Examples: Halides ( Fluoride, Chloride, Bromide, Iodide), Hydroxide, Cyanide, Ammonia, and Water are examples of Nucleophiles.
What is a base?
A base is an affluent electron species that gives electron pairs to a hydrogen atom to form a new covalent bond.
Examples: Halides ( Fluoride, Chloride, Bromide, Iodide), Hydroxide, Cyanide, Ammonia, and Water are examples of bases.
Give examples of a good nucleophile specie that is a good base?
Alkoxide ion (OR– ), Hydroxide ion (OH– ) or Azanide ion (NH2– ) are both good nucleophiles and good bases.
Give examples of poor nucleophile species that is a good base?
LiN[CH(CH₃)₂], t-BuO⁻, and t-BuLi are good bases but poor nucleophiles because of steric hindrance.
How will you distinguish between a good nucleophile and a poor nucleophile and a good base and a poor base?
We can distinguish between good and poor nucleophiles by measuring the reaction rate. In contrast, we can distinguish between good and poor bases by measuring the pKb value.
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