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Question
What are electrophiles and nucleophiles? Explain with examples.
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Solution
An electrophile is a reagent that takes away an electron pair. In other words, an electron-seeking reagent is called an electrophile (E+). Electrophiles are electron-deficient and can receive an electron pair.
Carbocations (`"CH"_3"CH"_2^+`) and neutral molecules having functional groups such as carbonyl group \[\begin{array}{cc}
\backslash\phantom{......}\\
(\ce{C = O})\\/\phantom{......}\\\end{array}\] are examples of electrophiles.
A nulceophile is a reagent that brings an electron pair. In other words, a nucleus-seeking reagent is called a nulceophile (Nu:).
For example: OH–, NC–, carbanions (R3C–), etc.
Neutral molecules such as H2Ö and ammonia also act as nulceophiles because of the presence of a lone pair.
RELATED QUESTIONS
Identify the reagents shown in bold in the following equation as nucleophiles or electrophiles:
\[\ce{C6H6 + \underline{\text{CH}_3\overset{+}{\ce{C}}{\ce{O}}} -> C6H5COCH3}\]
The reaction: \[\ce{CH_3CH_2I + KOH_{(aq)} -> CH_3CH_2OH + KI}\] is classified as ______.
Identify the reagents shown in bold in the following equation as nucleophiles or electrophiles:
\[\ce{CH3COOH + \underline{\ce{H}\overset{-}{\ce{O}}} -> CH3COO^- + H2O }\]
Identify the reagents shown in bold in the following equation as nucleophiles or electrophiles:
\[\ce{CH3COCH3 + \underline{\overset{-}{\ce{C}}\ce{N}} -> (CH3)2C(CN)(OH)}\]
Electrophiles are electron seeking species. Which of the following groups contain only electrophiles?
(i) \[\ce{BF3, NH3, H2O}\]
(ii) \[\ce{AlCl3, SO3, NO^{+}2}\]
(iii) \[\ce{NO^{+}2, CH^{+}3, CH3 - \overset{+}{C} = O}\]
(iv) \[\ce{C2H^{-}5, \overset{\bullet}{C2}H5, C2H^{+}5}\]
Nucleophile is a species that should have:
(i) A pair of electrons to donate
(ii) Positive charge
(iii) Negative charge
(iv) Electron-deficient species
Why does SO3 act as an electrophile?
Match the terms mentioned in Column I with the terms in Column II.
| Column I | Column II |
| (i) Carbocation | (a) Cyclohexane and 1-hexene |
| (ii) Nucleophile of | (b) Conjugation of electrons of C – H σ bond with empty p-orbital present at adjacent positively charged carbon. |
| (iii) Hyperconjugation | (c) sp2 hybridised carbon with empty p-orbital |
| (iv) Isomers | (d) Ethyne |
| (v) sp hybridisation | (e) Species that can receive a pair of electrons |
| (vi) Electrophile | (f) Species that can supply a pair of electrons |
