CARBOXYLIC ACIDS

CARBOXYLIC ACIDS• Carboxylic acids are a homologous series of organic acids which have the

carboxyl (-COOH) functional group

• They have the general formula CnH2n+1COOH

CARBOXYLIC ACIDSName Molecular formula Structural formula Full structural

formula

methanoic acid HCOOH HCOOH

ethanoic acid CH3COOH CH3COOH

propanoic acid C2H5COOH CH3CH2COOH

butanoic acid C3H7COOH CH3CH2CH2COOH

PHYSICAL PROPERTIES OF CARBOXYLIC ACIDS

Acid Boiling point /0Cmethanoic acid 101ethanoic acid 118propanoic acid 141butanoic acid 164

• The above carboxylic acids are all soluble in water.

• Boiling point increases as the molecular size increases.

CHEMICAL PROPERTIES OF CARBOXYLIC ACIDS• Carboxylic acids are weak acids because they ionise only partially in aqueous

solution.

• ethanoic acid ⇌ ethanoate ion + hydrogen ion

• CH3COOH(aq) ⇌ CH3COO-(aq) + H+(aq)

⇌ +

CHEMICAL PROPERTIES OF CARBOXYLIC ACIDS• Reaction with reactive metals

• carboxylic acid + metal salt + hydrogen

• ethanoic acid + magnesium magnesium ethanoate + hydrogen

• 2CH3COOH(aq) + Mg(s) (CH3COO)2Mg(aq) + H2(g)

CHEMICAL PROPERTIES OF CARBOXYLIC ACIDS• Reaction with carbonates

• carboxylic acid + carbonate salt + carbon dioxide + water

• ethanoic acid + sodium carbonate sodium ethanoate + carbon dioxide + water

• CH3COOH(aq) + Na2CO3(aq) 2CH3COONa(aq) + CO2(g) + H2O(l)

CHEMICAL PROPERTIES OF CARBOXYLIC ACIDS• Reaction with bases

• carboxylic acid + bases salt + water

• ethanoic acid + sodium hydroxide sodium ethanoate + water

• 2CH3COOH(aq) + NaOH(aq) CH3COONa(aq) + H2O(l)

CHEMICAL PROPERTIES OF CARBOXYLIC ACIDS

• Reaction with alcohols

PRODUCING ETHANOIC ACID• Oxidation by acidified potassium manganate (VII)

• ethanol + oxygen from oxidising agent + heat ethanoic acid + water

• CH3CH2OH(aq) + 2[O] + heat CH3COOH(aq) + H2O(l)

2+ + H2O

PRODUCING ETHANOIC ACID• Oxidation by atmospheric oxygen

• ethanol + oxygen from air + bacteria ethanoic acid + water

• CH3CH2OH(aq) + O2(g) + bacteria CH3COOH(aq) + H2O(l)

ESTERS• A sweet smelling compound called esters.

• An ester is a colourless liquid that is insoluble in water. The function group is:

ESTERS

• Esters are formed by the reaction of a carboxylic acid with an alcohol. This reaction is known as esterification.

ESTERIFICATION

• Ethanoic acid is warmed with ethanol in the presence of a few drops of sulfuric acid, water and an ester called ethyl ethanoate are formed. Concentrated sulfuric acid acts as a catalyst for the reaction.

ESTERIFICATION• ethanoic acid + ethanol + concentrated sulfuric acid ⇌ ethyl ethanoate +

water

• CH3COOH(aq) + C2H5OH(aq) + H2SO4(aq) ⇌ CH3COOC2H5(aq) + H2O(l)

• During the formation of ethyl ethanoate, the –OH group from ethanoic acid is replaced by the CH3-CH2-O- group from ethanol.

ESTERIFICATION

NAMING ESTERSReactants Ester formed

Acid Alcoholmethanoic acid

(HCOOH)ethanol

(C2H5OH)ethyl methanoate

(HCOOC2H5)ethanoic acid(CH3COOH)

methanol(CH3OH)

methyl ethanoate(CH3COOCH3)

ethanoic acid(CH3COOH)

ethanol(C2H5OH)

ethyl ethanoate(CH3COOC2H5)

The name of an ester consist of two parts. The first part is derived from the alcohol, the second part is derived from the carboxylic acid.

USES OF ESTERS

• Esters are used in perfumes, as artificial food flavourings and as solvents for cosmetics and glues.

• Permission is granted to you for personal use only. Contact admin@basecamp.sg for commercial or school usage.