Carboxylic Acid Lab Report

DERIVATIVES

Carboxylic acids

One of the derivatives of the carboxylic acid is the organic compound with a functional group of –COOH. Carboxylic acids are also can be divided into two main compounds; ie aromatic and aliphatic carboxylic acid. As such, we may refer to a chemical compound with two –COOH functional group as dicarboxylic acid. The following is an example of the common variation of carboxyl chemical compound:-

FIGURE:

Ethanoic acid (commonly known as acetic acid)

FIGURE:

1,1-Cyclohexanedicarboxylic acid

Physical properties of Carboxylic Acids

Generally, carboxylic acids have a relative higher boiling point and melting point compared to other organic compounds such as alcohols and hydrocarbons which are much likely prior

As such, it creates a stronger hydrogen bonding between H atom and O atom from carbonyl group of other carboxylic acids.

FIGURE:

The inductive effect of carbonyl compound is one of the contributing factor in high melting and boiling point.

One of the special properties of the carboxylic acid is the dimerization of such chemical compound through hydrogen bonding when dissolved in non-polar organic solvent.

FIGURE:

Dimerisation in carboxylic acid

Preparation of Carboxylic Acids

There are several ways to produce carboxylic acids as most of chemical reactions of organic compounds are inter-related. Common examples of such preparation are oxidation of primary alcohol and aldehydes accompanied by the hydrolysis of Nitriles compounds. The following are the chemical equations of such reaction taken place.

Oxidation of Primary Alcohols

RCH_2OH + 2[O] RCOOH + H_2 O

Oxidation of Aldehydes KMnO_4/"H" _"2" 〖"SO" 〗_"4"

RCHO + [O] RCOOH

The following is the reaction mechanism of carboxylic acid with thionyl chloride. Figure: Nucleophilic substitution of carboxylic acid

Physical properties of Acyl Chloride

Most of the acyl chlorides are colourless, fuming liquid at room temperature as acyl chlorides are readily to hydrolyse moist air to form carboxylic acid and white fume of hydrogen chloride. By the way, Acyl Chloride couldn’t form any hydrogen bonds with water molecules. In short, it has a lower boiling point than the corresponding carboxylic acid.

Chemical reaction of Acyl Chloride

The major reaction of an acyl chloride is nucleophilic substitution whereby the chlorine atom is substituted with nucleophile. The following is the general chemical equation of acyl chloride:- Hydrolysis

As mentioned, acyl chlorides are the reactive chemical compounds that readily react with moist air to form carboxylic acid and hydrogen chloride. In another words, it may dissolve in water. FIGURE: Chemical mechanism of acyl chloride through hydrolysis

Note:

If only limited water is available, e.g. like when the acid chloride liquid fumes in air, step (3) could be written as a chloride ion removing the proton to form hydrogen chloride