Solubility
Solubility and Functional Groups _______________________________________________________
You will recall from general chemistry that a solution has two components: the solvent, which is the substance present in greater amount, and the solute, which is dissolved in the solvent. Solubility is defined as the mass (in grams) of solute dissolved in 100 g of solute at saturation. Molar solubility is defined as the amount (in moles) of solute per liter of saturated solution. The solubility of one compound in another is related to the strength and type of intermolecular forces that exist between the two components. These forces arise from factors of molecular shape and electronegativity difference (∆χ), and are influenced by the specific functional groups contained within the molecule. A functional group is a group of atoms bonded in a particular way, with a predictable chemical and physical behavior. Examples are shown in Figure 1.
Figure 1. Examples of functional groups
The class of compound is given under each structure; the functional group name, if different, is in parentheses. H N amine (amino)
OH
Br alkyl bromide (bromo) alkene (alkenyl) O O H aldehyde ketone (carbonyl) alkyne (alkynyl) O
alcohol (hydroxyl)
O N C nitrile epoxide
ether
O OH carboxylic acid (carboxyl)
O Cl acyl halide (haloformyl)
O O
O
O O
O N H amide (carboxamide)
anhydride
ester
carboxylic acid derivatives
Solute molecules that experience strong intermolecular attractions to solvent molecules will be more likely to dissolve. On the other hand, if the solute molecules experience more attraction to each other than to the solvent molecules, then it is more energetically favorable for them to remain together and for the solvent particles to remain together, so
we would observe little solubility. Applying the broad generalization like dissolves like, we can make reasoned predictions about the solubility of a chosen substance in a given solvent. For
You will recall from general chemistry that a solution has two components: the solvent, which is the substance present in greater amount, and the solute, which is dissolved in the solvent. Solubility is defined as the mass (in grams) of solute dissolved in 100 g of solute at saturation. Molar solubility is defined as the amount (in moles) of solute per liter of saturated solution. The solubility of one compound in another is related to the strength and type of intermolecular forces that exist between the two components. These forces arise from factors of molecular shape and electronegativity difference (∆χ), and are influenced by the specific functional groups contained within the molecule. A functional group is a group of atoms bonded in a particular way, with a predictable chemical and physical behavior. Examples are shown in Figure 1.
Figure 1. Examples of functional groups
The class of compound is given under each structure; the functional group name, if different, is in parentheses. H N amine (amino)
OH
Br alkyl bromide (bromo) alkene (alkenyl) O O H aldehyde ketone (carbonyl) alkyne (alkynyl) O
alcohol (hydroxyl)
O N C nitrile epoxide
ether
O OH carboxylic acid (carboxyl)
O Cl acyl halide (haloformyl)
O O
O
O O
O N H amide (carboxamide)
anhydride
ester
carboxylic acid derivatives
Solute molecules that experience strong intermolecular attractions to solvent molecules will be more likely to dissolve. On the other hand, if the solute molecules experience more attraction to each other than to the solvent molecules, then it is more energetically favorable for them to remain together and for the solvent particles to remain together, so
we would observe little solubility. Applying the broad generalization like dissolves like, we can make reasoned predictions about the solubility of a chosen substance in a given solvent. For