Chapter 12: Problem 52
Which compound in each pair would you expect to be more soluble in water? Why? a. ethane or ethanol b. 2 -propanol or 2 -pentanol c. dibutyl ether or 1 -butanol
Short Answer
Expert verified
a. Ethanol; b. 2-Propanol; c. 1-Butanol. Solubility is higher with hydrogen bonding and shorter hydrocarbon chains.
Step by step solution
01
Identify the Nature of Ethane and Ethanol
Ethane is a nonpolar hydrocarbon, while ethanol is an alcohol with a hydroxyl group (-OH) that can form hydrogen bonds with water.
02
Solubility Comparison of Ethane and Ethanol
Since ethanol can form hydrogen bonds with water due to its hydroxyl group, it is more soluble in water than ethane, which is nonpolar and cannot form such bonds.
03
Identify the Nature of 2-Propanol and 2-Pentanol
Both 2-propanol and 2-pentanol are alcohols, but 2-propanol has a shorter hydrocarbon chain than 2-pentanol.
04
Solubility Comparison of 2-Propanol and 2-Pentanol
The shorter the hydrocarbon chain, the more soluble the alcohol in water. Hence, 2-propanol is more soluble in water than 2-pentanol.
05
Identify the Nature of Dibutyl Ether and 1-Butanol
Dibutyl ether is an ether and generally less polar than alcohols, while 1-butanol is an alcohol and can form hydrogen bonds with water.
06
Solubility Comparison of Dibutyl Ether and 1-Butanol
Since 1-butanol can form hydrogen bonds with water due to its hydroxyl group, it is more soluble in water than dibutyl ether, which is less polar.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polarity
Polarity is a key concept in determining the solubility of compounds in water. Simply put, polarity refers to the distribution of electric charge around molecules. Water is a polar molecule, meaning it has a positive end and a negative end. Because of this, polar molecules tend to dissolve well in water.
Nonpolar molecules, like ethane in the exercise example, do not dissolve well in water because there is no positive or negative end to attract the water molecules. On the other hand, ethanol is polar due to its -OH group (hydroxyl group), making it more soluble in water.
Nonpolar molecules, like ethane in the exercise example, do not dissolve well in water because there is no positive or negative end to attract the water molecules. On the other hand, ethanol is polar due to its -OH group (hydroxyl group), making it more soluble in water.
- Polar substances mix well with polar solvents like water.
- Nonpolar substances do not mix well with polar solvents.
Hydrogen Bonding
Hydrogen bonding is another crucial concept that affects solubility in water. A hydrogen bond is a weak bond between a slightly positive hydrogen atom and a slightly negative oxygen, nitrogen, or fluorine atom.
Water molecules form hydrogen bonds with each other, and they can form hydrogen bonds with other polar molecules that have O-H or N-H groups. This is why ethanol and other alcohols are highly soluble in water – their hydroxyl groups (O-H) can form hydrogen bonds with water molecules.
Water molecules form hydrogen bonds with each other, and they can form hydrogen bonds with other polar molecules that have O-H or N-H groups. This is why ethanol and other alcohols are highly soluble in water – their hydroxyl groups (O-H) can form hydrogen bonds with water molecules.
- Hydrogen bonds are important for the solubility of polar molecules in water.
- Molecules capable of hydrogen bonding with water dissolve better.
Hydrocarbon Chain Length
The length of the hydrocarbon chain in a molecule can significantly influence its solubility in water. Hydrocarbon chains are nonpolar and do not interact favorably with water, a polar solvent.
The shorter the hydrocarbon chain, the less nonpolar character the molecule has, making it more soluble in water. This is why 2-propanol, with a shorter hydrocarbon chain, is more soluble in water than 2-pentanol.
The shorter the hydrocarbon chain, the less nonpolar character the molecule has, making it more soluble in water. This is why 2-propanol, with a shorter hydrocarbon chain, is more soluble in water than 2-pentanol.
- Short hydrocarbon chains increase solubility in polar solvents like water.
- Long hydrocarbon chains decrease solubility in water.
Alcohols vs Ethers
Alcohols and ethers are both organic compounds, but their structures provide different solubility properties in water. Alcohols contain hydroxyl groups (-OH), which can form hydrogen bonds with water. This makes them generally more soluble in water compared to ethers, which lack this functional group.
In the exercise, 1-butanol (an alcohol) and dibutyl ether are compared. 1-butanol is more soluble in water because its -OH group allows it to form hydrogen bonds. Dibutyl ether, on the other hand, lacks this -OH group and is less polar, resulting in lower solubility in water.
In the exercise, 1-butanol (an alcohol) and dibutyl ether are compared. 1-butanol is more soluble in water because its -OH group allows it to form hydrogen bonds. Dibutyl ether, on the other hand, lacks this -OH group and is less polar, resulting in lower solubility in water.
- Alcohols can form hydrogen bonds with water, increasing their solubility.
- Ethers are generally less polar and less soluble in water.