Difference between the acid strength of inorganic and organic acids

[Rujano]

Homework Statement

Hi. I'm pretty much a beginner in organic chemistry and I'm just wondering something.

For example, I know that HCl is a stronger acid than HF.

But... then why the following happens if a have an organic acid (e.g a carboxylic acid)?

According to what I see, a carboxylic acid with a Cl substitutent is weaker than one with a F substituent.

Homework Equations

The Attempt at a Solution

I also know that because of electronegativity the difference between H and F is higher than that of H and Cl. So, that means that the bond between H and F is stronger, and therefore, the compoud is weaker ... am I right?

 

[AGNuke]

All Organic acids are weak acid (Generally). To determine the acidic strength, try forming their conjugate base on paper. Check their stability.

For F and Cl substituted Carboxylic acid, F exerts its inductive effect more than Cl, so it stabilizes the conjugate base by shifting the negative charge from -COO group to a wider area.

 

[JohnRC]

There is a huge difference in the trend in acid strength if we are looking at the atom directly bonded to the acidic hydrogen, or a more remote atom.
For directly bonded atoms:
HI > HBr > HCl > HF
H₂Se > H₂S > H₂O

For more remote atoms:
HONO₂ > HOPO₂
HOSO₂OH > HOSeO₂OH

Organic acids also follow this latter trend:

CH₂F.COOH > CH₂Cl.COOH > CH₃.COOH

 

[AGNuke]

The trend depends majorly on the stability of conjugate base. The better the CB is able to handle the negative charge on itself, the more acidic the acid. Simple Enough.

 

[DeeNos]

Hello,

The difference in acid strength between inorganic and organic acids can be attributed to several factors. Inorganic acids, such as HCl and HF, are typically stronger acids because they have a higher electronegativity difference between the hydrogen and the other atom, which results in a more polarized bond and easier dissociation of the hydrogen ion. Additionally, inorganic acids tend to have a smaller atomic radius, making it easier for the proton to be released.

In contrast, organic acids, such as carboxylic acids, have a lower electronegativity difference between the hydrogen and the other atom, resulting in a weaker bond and less dissociation of the hydrogen ion. They also tend to have larger atomic radii, making it harder for the proton to be released. Furthermore, the presence of additional groups on the organic acid molecule can also affect the acidity by either stabilizing or destabilizing the conjugate base.

In your example, the carboxylic acid with the F substituent is stronger because the fluorine atom is more electronegative than the chlorine atom, resulting in a stronger bond and easier dissociation of the hydrogen ion. However, there may be other factors at play as well, such as the presence of other groups on the molecule.

Overall, the difference in acid strength between inorganic and organic acids can be explained by a combination of factors, including electronegativity, atomic radius, and the presence of other groups on the molecule. I hope this helps clarify the concept for you. Keep up the good work in your studies!