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Why is the oxime tautomer more stable than its corresponding nitroso isomer?
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Ken Hill
Why is the oxime tautomer more stable than its corresponding nitroso isomer?
In keto-enol tautomerism generally the keto tautomer is more stable than its enol counterpart because in the former a significant ionic character exists which stabilises it. However, there are certain special cases. For instance if the enol form is aromatic(phenol), or very bulky mesityl groups are attached, etc.
In oxime-nitroso tautomerism however, the electronegativity difference comes into play.
In oxime, nitrogen is attached to carbon by a double bond;
and in nitroso, nitrogen is attached to oxygen by a double bond.
Now it is known that greater the difference in the electronegativity values, stronger is the bond. This property makes the nitrogen carbon double bondstronger hence making oximes more stable than nitroso.
In keto-enol tautomerism generally the keto tautomer is more stable than its enol counterpart because in the former a significant ionic character exists which stabilises it. However, there are certain special cases. For instance if the enol form is aromatic(phenol), or very bulky mesityl groups are attached, etc.
In oxime-nitroso tautomerism however, the electronegativity difference comes into play.
In oxime, nitrogen is attached to carbon by a double bond;
and in nitroso, nitrogen is attached to oxygen by a double bond.
Now it is known that greater the difference in the electronegativity values, stronger is the bond. This property makes the nitrogen carbon double bondstronger hence making oximes more stable than nitroso.
"it is known that greater the difference in the electronegativity values..." -- a reference would be good here, even a titorial type reference that has primary sources documented.More
sorry but I can not at all agree with the above answer! The greater the difference in electronegativity between 2 atoms, the weaker is the bond and not the reverse, when we compare atoms of the same period (C, N, O, F). For example H-F is the weakest (most acidic) linkage i.e., F-H More
@lemos The farther away the electronegativity values of 2 atoms, the stronger the bond generally is. Cesium has the lowest, and Fluorine has the highest and the make the strongest ionic bond. Be nice to people.More
I wonder if the $\alpha$ effect is in play here. Two hetero atoms with lone pairs bonded to each other have a weaker bond because of lone pair repulsion. This probably destabilizes the corresponding $\pi$ bond as well. That would favor the oxime.
I wonder if the $\alpha$ effect is in play here. Two hetero atoms with lone pairs bonded to each other have a weaker bond because of lone pair repulsion. This probably destabilizes the corresponding $\pi$ bond as well. That would favor the oxime.
In keto-enol tautomerism generally the keto tautomer is more stable than its enol counterpart because in the former a significant ionic character exists which stabilises it. However, there are certain special cases. For instance if the enol form is aromatic(phenol), or very bulky mesityl groups are attached, etc.
In oxime-nitroso tautomerism however, the electronegativity difference comes into play.
In oxime, nitrogen is attached to carbon by a double bond;
and in nitroso, nitrogen is attached to oxygen by a double bond.
Now it is known that greater the difference in the electronegativity values, stronger is the bond. This property makes the nitrogen carbon double bond stronger hence making oximes more stable than nitroso.
(electronegativity values: N=3.04, O=3.44, C=2.55)
In keto-enol tautomerism generally the keto tautomer is more stable than its enol counterpart because in the former a significant ionic character exists which stabilises it. However, there are certain special cases. For instance if the enol form is aromatic(phenol), or very bulky mesityl groups are attached, etc.
In oxime-nitroso tautomerism however, the electronegativity difference comes into play.
In oxime, nitrogen is attached to carbon by a double bond;
and in nitroso, nitrogen is attached to oxygen by a double bond.
Now it is known that greater the difference in the electronegativity values, stronger is the bond. This property makes the nitrogen carbon double bond stronger hence making oximes more stable than nitroso.
(electronegativity values: N=3.04, O=3.44, C=2.55)
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I wonder if the $\alpha$ effect is in play here. Two hetero atoms with lone pairs bonded to each other have a weaker bond because of lone pair repulsion. This probably destabilizes the corresponding $\pi$ bond as well. That would favor the oxime.
I wonder if the $\alpha$ effect is in play here. Two hetero atoms with lone pairs bonded to each other have a weaker bond because of lone pair repulsion. This probably destabilizes the corresponding $\pi$ bond as well. That would favor the oxime.
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