Which alcohol has the strongest intermolecular force of attraction? The weakest? Explain.
A. 1-Propanol
B. 1-Butanol
C. n-pentane
D. n-hexane
E. methanol
F. ethanol
We shall be happy to critique your thinking. Hint: look at the hydrogen bonding from the alcohols (and hydrogen bonding isn't present in n-pentane and n-hexane.)
butanol
has the strongest intermolecular force of attraction among the given options. This is because it has the longest carbon chain, which creates stronger dispersion forces (also known as van der Waals forces) in addition to the hydrogen bonding present in alcohols. The more carbons in the chain, the larger the molecule, and the stronger the dispersion forces between the molecules.
Methanol has the weakest intermolecular force of attraction among alcohols. This is because it has the shortest carbon chain (only one carbon) and thus weaker dispersion forces. However, it's important to note that alcohols generally have stronger intermolecular forces of attraction compared to non-alcohols, such as n-pentane and n-hexane, due to the presence of hydrogen bonding.
Since n-pentane and n-hexane lack hydrogen bonding, they will have weaker intermolecular forces compared to the alcohols. Among these two, n-pentane would have the weakest intermolecular force of attraction due to its shorter carbon chain and weaker dispersion forces compared to n-hexane.
The alcohol with the strongest intermolecular force of attraction is ethanol (F) since it can form hydrogen bonds. Hydrogen bonding occurs between the electronegative oxygen atom of one molecule and the hydrogen atom of another molecule. Ethanol has a -OH group that can form hydrogen bonds with other ethanol molecules, leading to stronger intermolecular attractions compared to other alcohols.
The alcohol with the weakest intermolecular force of attraction is n-pentane (C) or n-hexane (D). These compounds do not have a -OH group and therefore cannot form hydrogen bonds. The intermolecular forces in n-pentane and n-hexane are London dispersion forces, which are weaker than hydrogen bonding. London dispersion forces arise from temporary fluctuations in electron distribution and occur between all molecules, but are particularly weak in these alcohols without a hydroxyl group.
To determine the alcohol with the strongest intermolecular force of attraction, we need to consider the presence or absence of hydrogen bonding. Hydrogen bonding occurs when a hydrogen atom bonded to an electronegative atom (such as oxygen or nitrogen) interacts with another electronegative atom in a neighboring molecule.
In the given options, 1-Propanol, 1-Butanol, methanol, and ethanol all contain a hydroxyl group (-OH) that can participate in hydrogen bonding.
1-Propanol, 1-Butanol, and methanol have one hydrogen atom bonded to an oxygen atom, so they are capable of forming hydrogen bonds. Ethanol also has a hydrogen atom bonded to an oxygen atom and can participate in hydrogen bonding.
On the other hand, n-pentane and n-hexane do not contain any oxygen or nitrogen atoms capable of forming hydrogen bonds. Therefore, they do not experience hydrogen bonding.
Comparing the options, 1-Butanol has a longer carbon chain than methanol and ethanol. Since the intermolecular forces increase with longer carbon chains, 1-Butanol has stronger intermolecular forces of attraction compared to methanol and ethanol.
Therefore, among the given options, 1-Butanol has the strongest intermolecular force of attraction.
As for the alcohol with the weakest intermolecular force of attraction, we can conclude that n-pentane and n-hexane, which do not participate in hydrogen bonding, have weaker intermolecular forces compared to the alcohols that can form hydrogen bonds.
In summary:
- Strongest intermolecular force of attraction: 1-Butanol
- Weakest intermolecular force of attraction: n-pentane and n-hexane