If HCl is a weaker acid than HBr, why is ClCH₂COOH ...

Question

If HCl is a weaker acid than HBr, why is ClCH₂COOH a stronger acid than BrCH₂COOH?

Accepted Answer

Hey, everyone and welcome back in today's video. We're going to explain why floral acetic acid is more acidic than idle acetic acid. If Hydrofluoric acid is less acidic than hydro biotic asset. And first of all, let's draw the two structures that we are comparing floor acetic assets. So that will be our car broke silic acid group C 00 H. Then we have siege to you which responded to flooring. Now, the other one contains a car bookseller Cassis group CES two and iodine. Whenever we want to compare acidity, ease of two structures, we can think of their conjugate bases. So let's suppose that you add water to each of your structures and you will get corresponding conjugate bases, right? We are going to deal with a proton transfer. So we're going to use that acidic hydrogen bonded oxygen and we're going to draw those car box lit and ions. So we got our first one plus H 30 plus, right? Because the proton has been transferred to water. And for the 2nd 1, we get our car box late plus hydro nian. Once again. Now, in this case, we have to remember the inductive effect, the two structures are relatively similar. But whenever you have an exactly same position in each structure occupied by different atoms. In this case, Florinda and iodine, we are always considering the inductive effect. Notice that flooring is more electro negative, right. So we can say that flooring is more electro negative, then I died, right? Because flooring is pretty much the most electro negative atom that we observe in the periodic table. And when you go down the group, the electro negativity decreases. You may remember that both of them were intelligence, but iodine is below flooring and the pr disabled and therefore iodine must be less electro negative because flooring is more electro negative. That means it's more electron withdrawing, right. So we can clearly show these arrows with the electron flow from oxygen towards flooring. In addition, we may also indicate the arrow from the carbon ils oxygen because electrons are which one towards flooring. But in terms of the other car box light and iron, the electron flow towards iodine will not be so high because first of all, oxygen is more electro negative than iodine, right. So electrons will not flow that much towards iodine since it's not so electro negative to withdraw these electrons. So even though we have some of that right, because iodine is more electro negative than carbon, there will be some electron withdrawing effect by iodine but it will not be as strong as that. For flooring, we can state that if we think about the car box lit and are informed where we have our floral substitution, it's basically withdrawing electrons from oxygen and stabilized. The reason why it stabilizes basically because the electron density on negatively charged oxygen decreases. And if the electron density and oxygen decreases, that becomes a weaker conjugated base. Since whenever you decrease the electron density on your atom, it its lone pair becomes less efficient and less dense, meaning its capability of accepting a proton decreases. Right? We always want to make sure that the loan Paris concentrated and dance for a base to be strong. But if Florida's electron withdrawing is decreasing the electron density and oxygen and therefore the conjugate base of floor acetic asset will be stabilized and weaker G two inductive effect. While the conjugate base of I adore acetic asset will be stronger since iodine is not. So electron withdrawing, it has a much lower electro negativity and therefore, the negative charge and auction will be more concentrated and more dense, making that base a stronger base. So we understand that due to the fact that there's an inductive effect for both of these structures actually, but it's stronger for floor acetic acid because flooring is more electro negative than iodine. Therefore, floor ascetic will be more floor acetic acid will be more acidic due to the fact that it produces a more stable conjugate base than idle acetic acid. On the other hand, when we think about H F and H I were actually comparing that hydrogen Lorraine and hydrogen iodine bond and our hygiene is just bonded to these atoms directly. So we're not really considering an inductive effect. It's actually the atomic size that increases because iodine is bigger in size than Florence is. The greater size implies that that it is easier for us to remove that hydrogen in the form of an acidic proton. While Haijun Florin bond is stronger because flooring is a smaller atom, right? So it's harder for us to remove that hydrogen in the form of an acidic proton. Because the attraction force between hygiene and Florence is greater since Florin is smaller. And that's the main reason when we are considering H F and H I, it's actually the atomic size that we are considering. And when we compare floor acetic acid and I adore acetic acid, it's actually the inductive effect we are considering and we can state that the conjugate base of floor acetic acid is more stable because flooring is withdrawing the electron density from oxygen. And therefore, we may conclude that the correct answer to the multiple choice question is a Lorraine stabilizes the conjugate base of floor acidic asset by a stronger electron withdrawing effect. And that will be it. Thank you for watching. And I will see you in the next video

If HCl is a weaker acid than HBr, why is ClCH₂COOH a stronger acid than BrCH₂COOH?

Key Concepts

Acid Strength and Electronegativity

Inductive Effect

Comparative Acid-Base Strength

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Key Concepts

Acid Strength and Electronegativity

Inductive Effect

Comparative Acid-Base Strength

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If HCl is a weaker acid than HBr, why is ClCH₂COOH a stronger acid than BrCH₂COOH?