Why quinuclidine is a stronger base than aniline and N,N dimethyl aniline ?
Why quinuclidine is a stronger base than N,N dimethyl aniline ?
In N,N dimethyl aniline the electron pair on N-atom can undergo resonance with the ring through pi bond. So electron on N-atom in N,N dimethylaniline is not available for protonation
But in case of quinuclidine having a bridge bond which is perpendicular to the other ring and a flat N-atom is not possible and so resonance is inhibited.
That is, due to steric inhibition of resonance the electron pair on N-atom is more available for protonation and consequently,quinuclidine is a strong base than N,N dimethyl aniline.
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| Quinuclidine |
Why quinuclidine is a stronger base than aniline ?
In aniline the electron pair on N-atom can undergo resonance with the ring through pi bond.So electron on N-atom in aniline is not available for protonation.
But in case of quinuclidine the bridge is perpendicular to the other ring and a flat N-atom is not possible and so resonance is inhibited.
That is, due to steric inhibition of resonance the electron pair on N-atom is more available for protonation and consequently,quinuclidine is a strong base than aniline.
Why 1-phenylpiperidine is less basic than 3,4 dihydro-2H-1,4 ethanoquinoline?
The lone pair on N-atom in 1-phenylpiperidine undergoes resonance with the pi electrons of benzene ring , so it is unavailable for donation to Lewis acid.
But in 3,4 dihydro-2H-1,4 ethanoquinoline compound, due to presence a long bridge bond resonance is not possible .
Because the bridge bond is perpendicular to the other ring.Hence,lone pair of electron on N-atom is available for protonation.
Consequently the compound is more stronger base than 1-phenylpiperidine.
Summary :
Why quinuclidine is a stronger base than aniline and N,N dimethyl aniline ?
Why 1-phenylpiperidine is less basic than 3,4 dihydro-2H-1,4 ethanoquinoline ?
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