Chemistry Lecture 8: Carboxylic Acids

Organic compounds containing one or more carboxyl groups (-COOH) attached to a hydrocarbon chain.

The process of replacing a hydrogen atom in an alkane with a carboxyl group (-COOH).

The carboxyl group (-COOH) can lose a proton (H+) to form a carboxylate ion (RCOO-), making carboxylic acids acidic.

The strength of a carboxylic acid is influenced by factors like electronegativity of nearby atoms and the stability of the conjugate base.

The primary building blocks of many important organic compounds, including fatty acids, amino acids, and vitamins.

Compounds derived from carboxylic acids by replacing the hydroxyl group (OH) with other functional groups like -Cl (acid chloride), -OR (ester), or -NH2 (amide).

The systematic naming of carboxylic acids based on the longest carbon chain containing the carboxyl group.

Common names for carboxylic acids, often based on their sources or traditional uses.

The acidity constant (Ka) reflects the acid's strength. Strong acids have a large Ka, indicating a high concentration of H3O+ ions. Weak acids have a small Ka and a low H3O+ ion Concentration.

The pKa value is the negative logarithm of the Ka value. It provides a scale for comparing acid strengths.

Aromatic carboxylic acids are more acidic than phenols and alcohols. This difference is due to the electron withdrawing effect of the aromatic ring, which stabilizes the conjugate base.

Electronegativity is the attraction an atom has for electrons. Highly electronegative atoms, such as halogens, can pull electrons away from the carboxyl group, making the acid more acidic.

Inductive effects involve electron shifts due to the presence of electronegative atoms or groups. These effects can stabilize or destabilize the conjugate base, impacting the acid's strength.

Electron withdrawing groups (EWGs) stabilize the conjugate base of benzoic acid, making it more acidic. These groups pull electron density away from the carboxylate group.

Carboxylic acids can be prepared through several methods including oxidation of aldehydes, alcohols, and alkylbenzenes.

The strength of an acid is measured by its pKa value, a lower pKa indicates stronger acid. Benzoic acid has a lower pKa than acetic acid, meaning it is a stronger acid.

The phenyl group in benzoic acid has sp2 hybridized carbon atoms, which hold electrons closer to the carbon atom than sp3 hybridized carbon atoms. This electron-withdrawing effect makes the carboxyl group more acidic.

The inductive effect describes the electron-withdrawing or electron-donating effect of a group through a sigma bond. The phenyl group in phenylacetic acid exerts an inductive effect that increases the acidity of the carboxyl group.

Even though the phenyl group is closer to the carboxyl group in benzoic acid than in phenylacetic acid, benzoic acid is not significantly stronger than expected. This indicates that the inductive effect of the phenyl group on acidity is not as strong as expected.

Carboxylic acid derivatives are formed by replacing the -OH group of the carboxylic acid with different functional groups. For example, replacing -OH with -Cl gives an acid chloride, with -OR gives an ester, with -NH2, -NHR, -NR2 gives amides, and with -OOCR gives an anhydride.

Replacing the "oic acid" ending of the parent acid's name with "amide". If an R group is on the nitrogen, it's listed first and designated with "N-".

Replacing the word "acid" in the corresponding acid's name with the word "anhydride".

A chemical reaction where a nucleophile replaces a leaving group on a molecule.

Different carboxylic acid derivatives have different reactivities towards nucleophilic substitution, with acid chlorides being the most reactive and amides the least.

The IUPAC name for CH3COOCH2CH3.

Electron-withdrawing groups (EWGs) are substituents that pull electron density away from the benzene ring. This makes the ring less reactive towards electrophilic attack because the electron density is reduced.

The common name for CH3COOCH2CH3.

The IUPAC name for C6H5COOCH3.

Electron-donating groups (EDGs) are substituents that push electron density towards the benzene ring. This makes the ring more reactive towards electrophilic attack because the electron density is increased.

EWGs on benzoic acids increase acidity by stabilizing the conjugate base. They pull electron density away from the negatively charged carboxylate ion, reducing its charge and stabilizing it. This makes the acid more likely to donate a proton.

The common name for C6H5COOCH3.

EDGs on benzoic acids decrease acidity by destabilizing the conjugate base. They push electron density towards the negatively charged carboxylate ion, increasing its charge and destabilizing it. This makes the acid less likely to donate a proton.

The higher the s-character of an orbital, the closer its electrons are to the nucleus. This means an sp-hybridized anion is more stable than an sp2-hybridized anion, which is more stable than an sp3-hybridized anion. Increased stability of the conjugate base leads to increased acidity.

Delocalization of charge through resonance in the conjugate base anion stabilizes it. This stabilization can be visualized as spreading out the negative charge, reducing its concentration in any one location. More stable conjugate bases lead to stronger acids.

Acyl chlorides (RCOCl) are the most reactive carboxylic acid derivatives due to the strong electron-withdrawing effect of the chlorine atom. This makes the carbonyl carbon more susceptible to nucleophilic attack.

Electron-Withdrawing Groups (EWGs) increase the acidity of carboxylic acids by stabilizing the conjugate base. They do this by pulling electron density away from the carboxyl group.

Electron-Donating Groups (EDGs) decrease the acidity of carboxylic acids by destabilizing the conjugate base. They push electron density towards the carboxyl group, making it less likely to lose a proton.

Aromatic carboxylic acids are more acidic than phenols and alcohols because the aromatic ring stabilizes the conjugate base through resonance. This makes it easier for the carboxyl group to lose a proton.

Carboxylic acids are activated by converting them into derivatives that have better leaving groups. This makes the carbonyl carbon more susceptible to nucleophilic attack.

Acyl chlorides are prepared by reacting carboxylic acids with thionyl chloride (SOCl2) or phosphorus pentachloride (PCl5). The reaction often involves heat and a catalyst.

Acyl chlorides undergo a variety of reactions due to their reactivity. Common reactions include nucleophilic acyl substitution, reduction to aldehydes, and the formation of amides and esters.