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CHE110_Chapter_17_PowerPoint

Introduction to Carboxylic Acids and Esters

  • Carboxylic acids are organic compounds containing a carboxyl group (COOH).

  • Represented as RCOOH or RCO2H (R = hydrocarbon chain).

Esters

  • Esters are carbonyl compounds with an OR′ (alkoxy) group bonded to a carbonyl carbon.

  • Represented as RCOOR′.

  • The ester functional group is important in fats, oils, and other lipids.

  • Esters often have fruity scents and are used in the fragrance industry, responsible for the aroma in fruits (e.g., apples, bananas).

Hydrolysis of Esters

  • Esters react with water to form carboxylic acids and alcohols.

  • The mechanism involves breaking the ester bond and adding OH from water.

  • Hydrolysis can be catalyzed by acids or bases, leading to either carboxylic acids or carboxylate ions.

Carboxylic Acids in Health and Medicine

  • Pain relievers like ibuprofen and aspirin contain carboxyl groups, blocking prostaglandins to relieve pain.

The Role of Soap

  • Soaps are salts of carboxylic acids and have a dual nature: a polar head (ionic) and a nonpolar tail (hydrocarbon chain).

  • When dissolved in water, soap forms micelles, trapping nonpolar substances like grease.

  • The polar heads interact with water, allowing the release and washing away of the nonpolar substances.

Ester Formation

  • Esters are formed via Fisher esterification, where a carboxylic acid reacts with alcohol in the presence of an acid catalyst.

  • Example reactions include acetic acid and ethanol to form ethyl acetate and water.

Amides

  • Amides are derivatives of carboxylic acids where the -OH group is replaced by -NH2 (amine).

  • They are formed through the reaction of carboxylic acids with amines.

  • Amides play roles in various biological processes, including being constituents of proteins.

Penicillin

  • Discovered by Sir Alexander Fleming, penicillin has antibacterial properties by interfering with bacterial cell wall synthesis.

  • Structural features include a β-lactam ring common to all penicillins, contributing to its efficacy against bacteria.

Physical Properties

  • The boiling points of carboxylic acids are generally higher than alcohols of similar size due to their ability to form hydrogen bonds.

  • Esters typically have lower boiling points than carboxylic acids due to weaker intermolecular forces.

  • Hydrogen bonding significantly influences the physical state (solid, liquid) and boiling points of these compounds.