Carboxylic Acids and Esters Section 1.6

Carboxylic Acids Carboxylic Acid – an organic compound that contains a carboxyl group (COOH) Can easily lose a hydrogen ion when dissolved in an aqueous solution making the solution slightly acidic Citrus fruits, crabapples, rhubarb and other foods that contain carboxylic acids have a sour, tangy taste

Naming Carboxylic Acids Name the alkane name for the longest chain, including the carbon atom in the carboxyl group. Drop the “e” suffix of the root compound and replace it with the suffix “oic acid” The simplest aromatic carboxylic acid is benzoic acid Propanoic acid

Practice Name the following compounds: Draw 2-methylbutanoic acid hexanoic acid 4-chloropentanoic acid

Properties of Carboxylic Acids Since carbonxylic acids have 2 polar groups – carbonyl and a hydroxyl located close together, their molecules are very polar. The hydroxyl groups form hydrogen bonds with other molecules, making them very soluble in water. Larger carboxylic acids have decreasing solubility due to the large non-polar chain

Properties continued… Carboxylic acids share many properties with other acids Can be detected by litmus paper Carboxylic acids also react with bases to form ionic compounds and water. The melting points of carboxylic acids are higher than their hydrocarbon counterparts because of their polar parts

Esters Ester – an organic compound that contains a carbonyl group bonded to a second oxygen atom which is bonded to another carbon atom Many plants naturally produce esters which are responsible for many of the odours of fruits, flowers and perfumes. Synthetic esters are often used as flavourings in processed foods and as scents in cosmetics and perfumes.

Naming Esters Esters are formed by the condensation reaction of a carboxylic acid and an alcohol. The part that does not included the carbonyl group is named first and named the same way as a branch. The second part of the name comes from the carboxylic acid. The “oic acid” is replaced with “oate” pentyl butanoate

Practice Name the following ester: Draw the following ester: Butyl Ethyl methanoate Butyl Ethanoate

Properties of Esters The functional group is similar to the carboxyl group of an acid, but without the hydroxyl group. As a result esters are less polar than carboxylic acids and do NOT form hydrogen bonding. Small esters are soluble in water due to the polarity of the C-O bonds. Esters are less soluble than Carboxylic Acids and have lower boiling points.

Practice Naming decanoic acid butanoic acid 3-methyl heptanoic acid

Practice Drawing a) octanoic acid b) 3-methylpentanoic acid

Practice Naming ethyl pentanoate methyl decanoate butyl methanoate propyl benzoate

Practice Drawing a) methyl hexanoate b) methyl benzoate

Extra! Sometimes alcohol groups are not the parent chain and it is considered to be a branch. When it is a branch use “hydroxyl” Example: 3-hydroxyl-2-methylpentanal