What are the difference between Tautomerism & Resonance ?

(1) In tautomerism, an atom changes place but resonance involves a change of position of pi-electrons or unshared electrons.

(2) Tautomers are different compounds and they can be separated by suitable methods but resonating structures cannot be separated as they are imaginary structures of the same compound.

(3) Two tautomers have different functional groups but there is same functional group in all canonical structures of a resonance hybrid.

(4) Two tautomers are in dynamic equilibrium but in resonance only one compound exists.

(5) Resonance in a molecule lowers the energy and thus stabilises a compound and decreases its reactivity. But no such effects occur in tautomerism.

(6) In resonance, bond length of single bond decreases and that of double bond increases e.g. all six C—C bonds in benzene are equal and length is in between the length of a single and a double bond.

(7) Resonance occurs in planar molecule but atoms of tautomers may remain in different planes as well.

(8) Tautomers are indicated by double arrow in between the two isomers but double headed single arrow is put between the canonical (resonating) structures of a resonating molecule.

Related Questions:

(2) How is base strength related to the availability of the electron-pair

(3) Amines are more basic than ammonia why?

(4) What is relative basic strength order 1° amines , 2°amines and 3° amines ? Explain:

(5) Give an explanation for the fact that Guanidine NH=C(CH3)2 is a stronger base than most of amines?

(6) Arrange in correct order of basic Character of aniline, pyrrol, pyridine and piperidine?

(7) What is correct basicity order of pyridine, pyridazine, pyrimidine and pyrazine ?

(8) Give an explanation for the fact that Guanidine NH=C(CH3)2 is a stronger base than most of amines?

(9) Arrange in correct order of basic Character of aniline, pyrrol, pyridine and piperidine?

(10 What is correct basicity order of pyridine, pyridazine, pyrimidine and pyrazine ?

(11) Why pyridine is more basic than Pyrrole?

(12) Why pyrimidine is less basic than pyridine?

(13) Imidazole is more basic than pyridine? Why?

(14) Biological Important of Imidazole and structure:

(15) Pyridine is almost 1 million times less basic than piperidine? Why?

(15) Cyclohexylamine amine is the stronger base than Aniline? Why?

(16) Tetrahydroquinoline amine is the stronger base than Tetrahydroisoquinoline? Why?

(17) Arrange the following in the order of increasing basicity : p-Toluidine, N, N-Dimethyl-p-toluidine, p-Nitroaniline, Aniline. (I.I.T.1986)

(18) Arrange the following in the increasing order of their acid strength : Methyl amine, Dimethyl amine, Aniline, N-methyl aniline (I.I.T, 1988).