Carboxylic Acid Reactions - Online Tutor, Practice Problems & Exam Prep

Carboxylic acid reactions involve an acid-base interaction where a base removes a proton (H⁺) from a carboxylic acid, forming its conjugate base, the carboxylate anion. For instance, ethanoic acid reacts with a base to produce ethanoate. This transformation highlights the reactivity of carboxylic acids, such as ethanoic acid, which are classified as weak acids. The change in the name from 'oic acid' to 'oate' signifies the formation of the carboxylate anion, an essential concept in understanding organic acid-base chemistry and the behavior of carboxylic acids in various chemical environments.

Acid-Base Reaction

In this video we're going to take a look at carbacillic acid reactions. Now here we do this by examining acid base reactions. We're going to say under this type of reaction, a base reacts with a carbasilic acid which represents a weak acid.

If we take a look here, we have a carbacillic acid in the form of ethanoic acid. Here we're going to use some type of base which is going to remove an H⁺ from the carbosilic acid and in doing this creates its conjugate base form which is a carboxylate anion.

Now here the carboxylate anion, it's ending is different in its carbicolic acid form, it's OIC acid and it's carboxylate anion form. You change the OIC acid to O 8. So ethanoic acid becomes ethanoate, right.

So just remember when we're talking about a carboylic acid reaction, we're basically saying the carpacilic acid is an acid. We can tell from its name, and it's reacting with some type of base which removes an H⁺ from it, thereby creating a carboxylate anion product.

Carboxylic Acid Reactions Example

Predict the products form from the fall reaction between propanoic acid and ammonia, right? So here this is our acid ammonia, which is a neutral nitrogen compound we know is our weak base. Now since both of these species are weak, we know that we have reversible arrows to show that in equilibrium has been established.

If you don't remember this, make sure you go back and take a look at my videos when we talk about reactions and equilibrium between acids and bases. So we know, following the Bronsted-Lowry definition of acids and bases, that the carboxylic acid gives away an H+ to the ammonia. It becomes a carboxylate anion. In the process, the ammonia gains an H+ to become the ammonium ion, so it becomes NH4+.

So although we're talking about an organic molecule in terms of carboxylic acid, this is kind of familiar because it follows our Bronsted-Lowry definitions of acids and bases. The acid donates an H+, the base accepts the H+ and in that way we make our two ions as products.

Name the carboxylate anion formed in the following reaction.

• A. 2-methylpentanoate
• B. 4-methylhexanoate
• C. 4-methylpentanoate
• D. 2-methylhexanoate

Here’s what students ask on this topic:

Which of the following statements is not true about the reactions of carboxylic acid derivatives?

Carboxylic acid derivatives include a variety of compounds such as esters, amides, anhydrides, and acyl chlorides. These derivatives are all related to carboxylic acids but have different reactivity due to the nature of their substituents. Generally, acyl chlorides are the most reactive among these derivatives, followed by anhydrides, esters, and then amides, which are the least reactive. This reactivity is due to the differing abilities of the substituents to donate electrons to the carbonyl carbon, affecting its electrophilic character. The more electron-withdrawing the substituent, the more reactive the carbonyl compound will be towards nucleophilic attack. Additionally, the reactivity of these derivatives can be influenced by the presence of catalysts or the pH of the environment. It's important to consider these factors when predicting or understanding the behavior of carboxylic acid derivatives in various chemical reactions.

Which of the following reactions would not produce a carboxylic acid?

To determine which reaction would not produce a carboxylic acid, you need to consider the typical reactions that do produce carboxylic acids. Common methods include the oxidation of primary alcohols or aldehydes, hydrolysis of nitriles, and the oxidative cleavage of alkenes using strong oxidizing agents like potassium permanganate (${\mathrm{KMnO}}_4$) or ozone ($O_3$).

Reactions that do not lead to the formation of carboxylic acids include the reduction of aldehydes or ketones to alcohols, the alkylation of amines, and the dehydration of alcohols to form alkenes. Additionally, reactions like the Friedel-Crafts acylation, which forms ketones, or the addition of hydrogen halides to alkenes, which forms alkyl halides, also do not produce carboxylic acids.

So, in summary, any reaction that does not involve the oxidation of a molecule containing a primary alcohol or aldehyde group, or the hydrolysis of a nitrile, is unlikely to produce a carboxylic acid.

Which reactions yield the same carboxylic acid?

Carboxylic acids can be synthesized through various chemical reactions. Some of the common reactions that yield the same carboxylic acid include:

1. Oxidation of primary alcohols or aldehydes: When a primary alcohol or an aldehyde is oxidized, it can be converted into a carboxylic acid. This is typically done using oxidizing agents such as potassium permanganate (KMnO₄), chromium trioxide (CrO₃), or nitric acid (HNO₃).

2. Hydrolysis of nitriles: Nitriles, when hydrolyzed in the presence of acid (H⁺) or base (OH^-), will form carboxylic acids.

3. Hydrolysis of esters: Esters can be converted to carboxylic acids through hydrolysis, which involves breaking the ester bond in the presence of water and an acid or base catalyst.

4. The Grignard reaction with carbon dioxide: When a Grignard reagent (an organomagnesium compound) reacts with carbon dioxide (CO₂), it forms a carboxylic acid after hydrolysis.

5. Oxidation of alkylbenzenes: Alkylbenzenes can be oxidized to carboxylic acids if the alkyl group has at least one hydrogen atom.

Why does carboxylic acid not give reactions of carbonyl group?

Carboxylic acids contain a carbonyl group (C=O), but they don't typically undergo the same reactions as other carbonyl-containing compounds like ketones or aldehydes. This is primarily due to the presence of the hydroxyl group (OH) attached to the same carbon as the carbonyl group. This configuration leads to resonance stabilization, where the lone pair electrons on the oxygen of the hydroxyl group can delocalize onto the carbonyl carbon, spreading out the charge and stabilizing the molecule.

Furthermore, the electronegative oxygen of the hydroxyl group draws electron density away from the carbonyl carbon, making it less electrophilic and less reactive towards nucleophilic addition, which is a common reaction of aldehydes and ketones. Additionally, the carboxylic acid can form intermolecular hydrogen bonds, which further reduces the reactivity of the carbonyl carbon.

Instead of typical carbonyl reactions, carboxylic acids tend to undergo reactions that involve the OH group, such as forming esters in the presence of alcohols (esterification) or converting to acyl chlorides with reagents like thionyl chloride. These reactions exploit the acidic nature of the hydroxyl hydrogen rather than the reactivity of the carbonyl group itself.