Acid

An acid has a pH value lower than 7. It is a substance that will react with water to produce H₃O⁺ and with a base to neutralise to water and a salt. On a universal indicator, strong acids show up as a red or dark orange colour, and weaker acids show up as an orange or yellow colour.

Acid can cause serious damage to human health. The correct PPE (Personal Protective Equipment) should be worn when working with acids.

Acids can be and often are used as catalysts in chemical reactions such as the reaction between amide nucleophiles and imines. Using a Bronsted Lowry acid for this reaction produced an extremely high yield more than 99%^[1].

Also see alkali.

Brønsted Lowry Acid

A molecule that donates a proton, in the form of a hydrogen ion.

Lewis Acid

A Molecule that can accept a pair of electrons.

Structure - ends with -COOH

Hydrochloric acid

HCl

H⁺ Cl^-

References

1. ↑ Rowland GB, Zhang H, Rowland EB, Chennamadhavuni S, Wang Y, Antilla JC. Brønsted acid-catalyzed imine amidation. Journal of the American Chemical Society. 2005 Nov 16;127(45):15696-7.