Explain why the boiling point of ethyl alcohol (C2H5OH, 78.4 oC) is higher than the boiling point of methyl alcohol (CH3OH, 64.7 oC).
The boiling point of a substance is determined by the strength and types of intermolecular forces present in the molecule. In the case of ethyl alcohol (C2H5OH) and methyl alcohol (CH3OH), both compounds have polar bonds due to the presence of oxygen bonded to hydrogen.
However, in ethyl alcohol (C2H5OH), the ethyl group (C2H5) has a larger molecular size and more electrons compared to the methyl group (CH3) in methyl alcohol (CH3OH). This results in increased surface area and a larger number of electron-cloud interactions between adjacent molecules.
As a result, ethyl alcohol has stronger London dispersion forces (also known as Van der Waals forces) compared to methyl alcohol. These forces are caused by temporary shifts in electron density, leading to temporary positive and negative charges that attract neighboring molecules.
The stronger London dispersion forces in ethyl alcohol require more energy to overcome, thus increasing its boiling point compared to methyl alcohol, which has weaker London dispersion forces.
Additionally, ethyl alcohol also has stronger hydrogen bonding due to the presence of the -OH group in its structure. Hydrogen bonding occurs when hydrogen is bonded to an electronegative atom such as oxygen or nitrogen, creating a strong dipole-dipole interaction between molecules.
The presence of stronger hydrogen bonding in ethyl alcohol further contributes to its higher boiling point compared to methyl alcohol, which has weaker hydrogen bonding.
In summary, the boiling point of ethyl alcohol is higher than methyl alcohol due to its larger molecular size, increased electron-cloud interactions, stronger London dispersion forces, and stronger hydrogen bonding.
The boiling point of a substance is determined by the strength of intermolecular forces between its molecules. In the case of ethyl alcohol (C2H5OH) and methyl alcohol (CH3OH), both molecules have similar molecular weights and similar molecular structures, which means they have similar types of intermolecular forces. However, the ethyl alcohol molecule has one additional carbon atom (C) compared to the methyl alcohol molecule. This additional carbon atom increases the molecular size of ethyl alcohol, leading to stronger intermolecular forces.
To explain this further, we can look at the types of intermolecular forces at play. Both ethyl alcohol and methyl alcohol exhibit London dispersion forces, which are temporary attractions between molecules caused by the shifting of electrons. These forces increase with the number of electrons in a molecule and therefore, with the molecular size.
With the additional carbon atom in ethyl alcohol, there are more electrons in the molecule compared to methyl alcohol. As a result, ethyl alcohol experiences stronger London dispersion forces, leading to higher boiling point.
Additionally, ethyl alcohol also exhibits hydrogen bonding, which is a stronger type of intermolecular force. Hydrogen bonding occurs when a hydrogen atom is bonded to an electronegative atom (like oxygen or nitrogen) and forms a polar bond with another electronegative atom in a neighboring molecule.
In the case of ethyl alcohol, the oxygen atom is bonded to two hydrogen atoms, allowing for the formation of hydrogen bonds. Methyl alcohol also has the potential for hydrogen bonding but to a lesser extent since it has only one hydrogen atom bonded to the oxygen atom.
The presence of hydrogen bonding in ethyl alcohol increases the strength of intermolecular attractions even further, thus elevating its boiling point compared to methyl alcohol.
In summary, the higher boiling point of ethyl alcohol compared to methyl alcohol can be attributed to the larger molecular size, leading to stronger London dispersion forces, and the presence of hydrogen bonding, which further increases the intermolecular attractions.