29@Asish can u plz explain this So it pulls the electrons towards itself... hence it shortens the C-O bond..
however the reason wat i feel for this effect is......since the number of protons in the Oxygen nucleus are more than the number of protons in carbon nucleus...so they will attract the shared pair of electrons more strongly ..hence decreasing the C=O bond length...
49yea the stabler one dominates in the equilibrium mixture!![1][1]
39The tautomerization is too small to be noticed, Soumik...0.01% enol and rest keto. It is a case of dynamic equilibrium, and on addition of reagent tautomerization to enol occurs but almost immediately it shifts back to enol, unless there is an extra reagent which causes the equilbrium to shift largely(I think). The equilibrium lies largely to the keto side in normal cases.
@govind, about that MO explanation of C=O's greater stability..I think I read it in Peter Skyes...can't remember!
11Now let me add my qsn - if keto is more stable than enol, then why does it at all tautomerise in acid/basic medium?
49ya thanks...
actually the q was y generally keto is stabler than enol...the reason is as C=O is stronger than C=C...[1][1][1]
29I meant how pulling of electrons towards one side decreases the bond length?...
though i feel that the reason behind this is electrostatic attraction b/w the nucleus and electrons due to which the nucleus tries to pull the shared pair...hence the ovelap of electrons become more strong..tgus reducing the bond length..
1that is what asish wants to say,
Oxygen being more electronegative pulls the bond pair of electrons towards itself as in case of dipole, hence pulling the electrons shortens the bond length hence attraction of nucleus and electrons increases so more stable and more energy is required to break the bond...
39govind it means
generally a atom of highger electro negativity tends to keep the shared pair of electrons towards its side..
so the O here tries to keep them towards it and hence pulls the pair of electrons towards itself :)
106@subhomoy.... =C=C= or -C=C- ?
cumulated trienes =C=C= are quite unstable
49well i tht electronegativity only caused shifft in e- pair...
OMG hw confusing chem is!!!
106electronegativity affects a lot of things...
for the same reason,
C-H bond length in CH3-NO2 is less than that in CH4..
Due to higher electronegativity of NO2- grp... (or due to -I effect)
49OMG hw come electronegativity start affecting bond length???
106O has very high electronegativity.. So it pulls the electrons towards itself... hence it shortens the C-O bond..
Now as shorter bonds => stronger bonds ..hence the order
i really dunno much more than this
49ok....but rather than bond energy is there any other explanation???coz hw the hell are we supposed to remember in examination hall whch has hw much bond energy??
106Bond energy of C=O is more than C=C..
So, C=O is more stable than C=C
49well actually the question was C=O or C=C bond whch is more stable??