Question

A codeine-containing cough syrup lists codeine sulfate as a major ingredient instead of codeine. The Merck Index gives${\mathbf{\text{C}}}_{\mathbf{\text{36}}}{\mathbf{\text{H}}}_{\mathbf{\text{44}}}{\mathbf{\text{N}}}_{\mathbf{\text{2}}}{\mathbf{\text{O}}}_{\mathbf{\text{10}}}\mathbf{\text{S}}$as the formula for codeine sulfate. Describe the composition of codeine sulfate (see Exercise ). Why is codeine sulfate used instead of codeine?

Short answer

Composition: 2(C₁₈H₂₁NO₃). H₂SO₄

Codeine sulfate is used instead of codeine as it is safer and soluble.

Step-by-step solution

State composition of codeine sulfate 

Formula of Codeine sulfate: C₃₆H₄₄N₂O₁₀S

Its composition is 2 molecules of codeine and one molecule of sulphuric acid, i.e. 2(C₁₈H₂₁NO₃). H₂SO₄.

Explain why codeine sulfate is safer 

The chemical formulae for codeine and codeine sulphate are${\text{C}}_{\text{18}}{\text{H}}_{\text{21}}{\text{NO}}_{\text{3}}$and${\text{C}}_{\text{36}}{\text{H}}_{\text{44}}{\text{N}}_{\text{2}}{\text{O}}_{\text{10}}\text{S}$, respectively.

From${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$, two molecules of codeine receive two protons.

Two conjugate acids of codeine${\text{C}}_{\text{18}}{\text{H}}_{\text{21}}{\text{NO}}_{\text{3}}{\text{H}}^{\text{+}}$and one sulphate ion${\text{SO}}_{\text{2}}^{\text{4 -}}$make up the sulphate salt known as codeine sulphate.

Since codeine sulphate is a salt, it is used in place of codeine. Ionic molecules called salts are particularly soluble in water.

As a result, the soluble medication codeine sulphate can enter the circulation and reach its intended destination within the body more easily.

Therefore, codeine sulphate is used instead of the codeine, as it is a soluble salt.