Inductive and mesomeric effects Flashcards
nucleophile
-ve ion, electron rich species, attracted to positively charged atoms
electrophile
+ve ion, electron deficient species, attracted to negatively charged atoms
Inductive effect
- withdrawal or donation of electron density along a sigma bond.
- The effect diminishes rapidly as chain length increases
How did inductive effect occur?
- the electrons are attracted towards the most electronegative atom.
- the polarization of the electron density of a sigma bond caused by the electronegativity of a nearby atom
+I effect
- electron donating inductive effect (EDG)
- when atttached to carbon, less electronegative, electrons attracted to carbon
-I effect
- electron withdrawing inductive effect (EWG)
- when attached to carbon, more electronegative, electrons is pulled from carbon
-I effect groups example
ie.Br, Cl, OH, NO2, NH2, CN, CHO, COOH
+I effect groups example
ie Alkyl groups, CH3… Mg, Li
Mesomeric effect
- also known as resonance
- withdrawal or donation of electron density, operates via pi and lone pair electrons
- Effect does not decrease with increasing distance (in conjugated systems)
How did mesomeric effect occur?
-the re-distribution of electrons which takes place in unsaturated molecules and especially in conjugated systems via their pi bonds.
+M effect groups example
+ M groups generally contain a lone pairs of electrons or a pi bond
ie Cl, OH, alkenes
-M effect
electron withdrawing mesomeric effect (EWG)
-pi system accepts electrons
+M effect
- electron donating mesomeric effect (EDG)
- pi system donates electrons or lone pair is donated
orto
2
para
4
