C+, N+, O+ - which is most acidic and why?

[HealthE]

I am working on some MCAT problems but I can't seem to remember how to determine the acidity for these carbon, nitrogen, and oxygen cations. Please help. Thanks.

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[Testosterone]

Since these are electron deficient, they are all relatively strong lewis acids. I would postulate that the more electronegative elements would have the higher affinity for accepting electrons. Then the order in terms of acidity would be O+ > N+ > C+.

 

[imbackasd]

Acidity increases with electronegativity across a table

 

[sciencebooks]

I am working on some MCAT problems but I can't seem to remember how to determine the acidity for these carbon, nitrogen, and oxygen cations. Please help. Thanks.

Just a little trick for the trends, I draw a square with the corners labeled B, E, A, R (counter clockwise).

B---------E
|-----------|
|-----------|
R--------A

As you point to the B (up and left), basicity increases.

As you point to the E (up and right), everything starting with E increases (electronegativity, electron affinity, etc.).

As you point to the A, acidity increases.

As you point to the R, radius increases.

Obviously, it's best to understand WHY, but I use this trick at least once per FL or set of practice passages.

 

[hmania]

Just a little trick for the trends, I draw a square with the corners labeled B, E, A, R (counter clockwise).

B---------E
|-----------|
|-----------|
R--------A

As you point to the B (up and left), basicity increases.

As you point to the E (up and right), everything starting with E increases (electronegativity, electron affinity, etc.).

As you point to the A, acidity increases.

As you point to the R, radius increases.

Obviously, it's best to understand WHY, but I use this trick at least once per FL or set of practice passages.

Nice shortcut!

 

[LoLCareerGoals]

Nice but trivialized short-cut. Acidity increases going down toward A only for binary acids, that trend is not correct for oxyanions: HClO4 is a stronger acid than HBrO4 etc.

 

[HealthE]

I read the reverse somewhere else...hmm that a carbon cation in really unstable so wants to get rid of the positive charge which makes it more acidic compared to the oxygen. Which is right?

 

[Charles Darwin]

I read the reverse somewhere else...hmm that a carbon cation in really unstable so wants to get rid of the positive charge which makes it more acidic compared to the oxygen. Which is right?

That's wrong. Generally speaking, the more electronegative an atom is, the more unstable it will be with a positive charge.