Understanding Solubility: Leucoindigo vs Blue Indigo

Why Leucoindigo is Water-Soluble and Blue Indigo is Not

As indigo makes hydrogen with itself making it non-polar, it remains insoluble in water whereas due to the basic property of leucoindigo, it acts as a polar compound becoming soluble in water.

With itself, indigo forms hydrogen bonds. The molecule is unable to form a connection with water as a result. Additionally, the molecule is quite symmetrical and has polar bonds with oppositely oriented dipole moments that cancel each other out, making it non-polar and insoluble in water. While water cannot dissolve apolar molecules, it may dissolve polar ones. In this manner, the leuco base of indigo is formed, resulting in a polar molecule that may dissolve in water. This leuco base is polar since it is a sodium salt.

Definition of Polar and Non-Polar Compounds

Polar compounds are compounds that have slight charges (slightly positive and slightly negative) within the compound. The slight charges are due to electronegativity differences of 0.3 to 1.4. Nonpolar compounds are compounds that do not have slightly negative and positive charges within the compound. The electronegativity differences of nonpolar compounds are between 0 and 0.2.

What do you mean by polar and non-polar compounds?

Polar compounds are compounds that have slight charges (slightly positive and slightly negative) within the compound. The slight charges are due to electronegativity differences of 0.3 to 1.4. Nonpolar compounds are compounds that do not have slightly negative and positive charges within the compound. The electronegativity differences of nonpolar compounds are between 0 and 0.2.

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