Rank these from lowest boiling point to highest.
CH4
CH3CH2CO2CH2CH3
CH3(CH2)2C=ONH2
CH3COOH
To rank these compounds from lowest boiling point to highest, we need to consider their molecular structures and intermolecular forces.
1. CH4 (Methane):
Methane is a simple hydrocarbon composed of one carbon atom bonded to four hydrogen atoms. It is an example of a nonpolar molecule. Since it does not have any strongly electronegative atoms and has only weak London dispersion forces between its molecules, it has the lowest boiling point among the given compounds.
2. CH3(CH2)2C=ONH2 (2-Aminobutane):
This compound contains a primary amine group (-NH2) and a chain of four carbon atoms. The amine group has a lone pair of electrons, making it capable of forming hydrogen bonds with other molecules. Hydrogen bonding is stronger than London dispersion forces, so 2-aminobutane has a higher boiling point compared to methane.
3. CH3CH2CO2CH2CH3 (Ethyl acetate):
Ethyl acetate consists of an ester group (CO2) and an ethyl group (CH2CH3). Although ester groups can participate in hydrogen bonding, the presence of the longer hydrocarbon chain in ethyl acetate decreases the overall boiling point compared to 2-aminobutane.
4. CH3COOH (Acetic acid):
Acetic acid contains a carboxyl group (-COOH), which can form multiple hydrogen bonds. The hydrogen bonding in acetic acid is stronger than the hydrogen bonding in the previous compounds due to the presence of the carboxyl group. Thus, it has the highest boiling point among the given compounds.
Therefore, the ranking from lowest boiling point to highest is:
CH4 < CH3(CH2)2C=ONH2 < CH3CH2CO2CH2CH3 < CH3COOH