Solubility of organic compound

organic chemistry II lab

Solubility of organic compound

Solubility: Solubility is a characteristic physical property

referring to the ability for a given substance, the solute, to dissolve in a solvent. It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution is called a saturated solution

Solubility of organic compound

Solute: Any substance that is dissolved in a liquid

or gas substance (solvent) to create a solution

Solvent: A solvent is a liquid or gas that dissolves a

solid, liquid, or gaseous solute, resulting in a solution.

Solubility of organic compound

Solubility rules: That simple rule is “like dissolves like” and it is based

on the polarity of the systems i.e. polar molecules dissolve in polar solvents (e.g. water, alcohols)

and non-polar molecules in non-polar solvents (e.g. the hydrocarbon hexane). This is why ionic compounds like table salt (sodium chloride) or compounds like sugar, dissolve in water but not most organic solvents.

The polarity of organic molecules is determined by polar bonds1 due to the presence of electronegative atoms (e.g. N, O) in polar functional groups such as amines (-NH2) and alcohols (-OH )

Solubility of organic compound

Solubility rules: As the percentage of the hydrocarbon portion

increases, water solubility decreases and ether solubility increases.

Solubility of organic compound

Solubility rules: Generally, solubility of a substance is

inversely related to its melting point: high melting point –low solubility.Solubility of organic compound

Solubility of organic compound

Solubility rules: In general, an increase in molecular weight leads to

an increase in intermolecular forces in a solid and decreased solubility.

Similarly, glucose vs. starch or cellulose, and amino acids vs. proteins

Solubility of organic compound

Solubility rules: Compounds having a branched chain is more

soluble than the corresponding straight-chain compound.

Branching lowers intermolecular forces and decreases intermolecular attraction.

Note:

(Intermolecular Forces of Attraction - Forces of attraction that exist between molecules(

Solubility of organic compound

Solubility rules: The position of the functional group in the

carbon chain also affects solubility.

Solubility of organic compoundSolubility Classification:

Solvent Some solubility or complete miscibilityWater alcohols, aliphatic amines, acids, esters,

ketones, aldehydes, carbohydrates (typically only those with 4 carbons or fewer)

Ether most organic molecules( alcohols, aldehydes, ketones, amines, esters, lipids, phenols)

5% NaOH carboxylic acids and phenols5% HCl Aromatic & aliphatic amines5% NaHCO3

carboxylic acids

Conc.H2SO4

alcohols, aldehydes, ketones, esters.

THE END