Question

Arrange these compounds in order of increasing solubility in water.

Short answer

Question: Arrange the given compounds - hexane, 1-pentanol, and 1,4-butanediol - in the order of increasing solubility in water based on their polarity and hydrogen bonding ability. Answer: Hexane (least soluble), 1-pentanol (medium solubility), 1,4-butanediol (most soluble)

Step-by-step solution

The given compounds are: 1. Hexane: \(\mathrm{C}_{6} \mathrm{H}_{14}\) - (smiles)CCCCCC(/smiles) 2. 1-pentanol: \(\mathrm{C}_{5} \mathrm{H}_{11} \mathrm{OH}\) - (smiles)CCCCCO(/smiles) 3. 1,4-butanediol: \(\mathrm{C}_{4} \mathrm{H}_{8} (\mathrm{OH})_{2}\) - (smiles)OCCCCO(/smiles) #Step 2: Determine the polarity of the compounds#

Polarity of a compound is determined by its molecular structure and the presence of polar functional groups. Let's analyze each compound: 1. Hexane is a nonpolar hydrocarbon, due to its linear carbon chain and absence of polar functional groups. 2. 1-pentanol is a polar compound, as it has an -OH group attached to the carbon chain. The oxygen atom in the -OH group has high electronegativity, giving polarity to the molecule. 3. 1,4-butanediol is also a polar compound, having two -OH groups in its structure, giving it even higher polarity than 1-pentanol. #Step 3: Evaluate the ability of the compounds to form hydrogen bonds with water#

Hydrogen bonding is an essential factor in determining the solubility of compounds in water. The ability of a compound to form hydrogen bonds depends on the presence of functional groups capable of hydrogen bonding. Let's analyze each compound: 1. Hexane does not have a functional group (-OH, =O, or -NH) that can form hydrogen bonds; hence it has the least ability to hydrogen bond with water molecules. 2. 1-pentanol has one -OH group which is capable of hydrogen bonding with water molecules. 3. 1,4-butanediol has two -OH groups, providing it with a greater ability than 1-pentanol to form hydrogen bonds with water molecules. #Step 4: Arrange the compounds in order of increasing solubility in water#

Based on the polarity and hydrogen bonding ability of the compounds, we can arrange them in the order of increasing solubility in water: 1. Hexane (least soluble) 2. 1-pentanol (medium solubility) 3. 1,4-butanediol (most soluble)

Key concepts

Polarity of Compounds

Understanding the concept of polarity is essential when studying solubility. Polarity refers to the distribution of electric charges around a molecule, which influences how it interacts with other substances. A compound is considered polar when there is a significant difference in electronegativity between its atoms, leading to an uneven charge distribution. Such molecules tend to have positive and negative poles.

Take the example of 1-pentanol, with an -OH (hydroxyl) group. The electronegativity difference between oxygen and hydrogen creates a dipole, making 1-pentanol polar. Contrast this with hexane, which lacks such polar functional groups and has a more even distribution of electrical charge, resulting in a nonpolar characteristic. Polarity directly affects solubility as polar substances are more likely to be soluble in polar solvents like water, due to the 'like dissolves like' principle.

Hydrogen Bonding

Hydrogen bonding is a special type of dipole-dipole attraction, which occurs when a hydrogen atom bonded to a highly electronegative atom, such as oxygen, nitrogen, or fluorine, is attracted to a lone pair of electrons on another electronegative atom. This interaction is particularly strong and plays a critical role in the solubility of compounds in water.

1,4-butanediol is an exemplary molecule where hydrogen bonding plays a key role. This compound contains two hydroxyl groups capable of forming hydrogen bonds, thus significantly increasing its affinity for water. In comparison, hexane's lack of such groups results in poor solubility in water. The strength and number of hydrogen bonds a molecule can form can greatly influence how well it dissolves in water.

Functional Groups in Organic Chemistry

Functional groups are specific groupings of atoms within molecules that have characteristic properties and behaviors. In organic chemistry, these groups determine the polarity and reactivity of molecules, impacting their interactions with other chemicals, including their solubility in solvents.

For instance, the hydroxyl group (-OH) found in alcohols, like 1-pentanol and 1,4-butanediol, is known for its polar nature and ability to engage in hydrogen bonding. Functional groups are like a molecule's 'social network,' dictating who it interacts with, how it behaves in reactions, and where it can dissolve. The presence or absence of these groups can significantly affect a compound's solubility profile in water.