Basicity of Functional Groups

[aeraqua]

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Could someone help me understand why amines are more basic than esters? Esters are resonance stabilized therefore I would expect the carbonyl O to be a better e donor, especially because it has a partial negative charge unlike the N in amine.

In addition, Chad (from Chad's Videos) talks about using CARDIO (Charge, Atom, Resonance, Dipole Induction, Orbital in this order) in this order to determine basicity, but has anyone found a better set of rules for this? For instance it doesn't work in this scenario where charge is presumably not the most important factor.

Thanks in advance!

 

[Czarcasm]

Could someone help me understand why amines are more basic than esters? Esters are resonance stabilized therefore I would expect the carbonyl O to be a better e donor, especially because it has a partial negative charge unlike the N in amine.

In addition, Chad (from Chad's Videos) talks about using CARDIO (Charge, Atom, Resonance, Dipole Induction, Orbital in this order) in this order to determine basicity, but has anyone found a better set of rules for this? For instance it doesn't work in this scenario where charge is presumably not the most important factor.

Thanks in advance!

Keep in mind basicity strength is directly related to stability. The more stable it is, the less 'basic' or reactive it will be. Resonance highly stabilizes the negative charge on the ester. The charge delocalizes between both oxygen atoms and is shared between the two. Think about all the strong acids in General Chemistry that are involved in resoance: Sulfuric Acid and Nitric Acid. The reason why they are strong acid is because their conjugate bases are very stable (due to resonance). Now, if you consider an amine, it has a free lone pair of it's own that's not involved in sharing and therefore is more reactive (basic). I guess you can think of it as being more available to react since it doesn't have to share.

 

[Czarcasm]

Could someone help me understand why amines are more basic than esters? Esters are resonance stabilized therefore I would expect the carbonyl O to be a better e donor, especially because it has a partial negative charge unlike the N in amine.

In addition, Chad (from Chad's Videos) talks about using CARDIO (Charge, Atom, Resonance, Dipole Induction, Orbital in this order) in this order to determine basicity, but has anyone found a better set of rules for this? For instance it doesn't work in this scenario where charge is presumably not the most important factor.

Thanks in advance!

By the way, as far as the 'CARDIO' rules, I'm not entirely familiar, but from what it seems, it's ranking base strength. For instance, an atom with a full negative charge is more basic than an atom with no charge: (ie. NH2- vs. NH3). An atom that's more leftward on the periodic table is more basic than those towards the right, due to electronegativity strength: (ie. NH3 vs. H2O). An electronegative atom hogs electrons to itself, and so a less electronegative atom is more willing to react.

An atom with resonance is less basic than one without, due to delocalization of electron density.
Inductive effect (specifically by nearby electronegative atoms) is also highly stabilizing (although resonance is considerably more significant); Together, both would make a base extremely stable.

Orbital I believe refers to the hybridization of the base: a negative charge on an sp carbon is more stable than sp2, which is more stable than sp3 (electron density is farther away from the nucleus on average and least stable).

 

[aeraqua]

Thanks for the help! It makes sense now, much appreciated 🙂