The difference in boiling point and heat of vaporization between ethyl acetate and methyl acetate can be attributed to variations in molecular structure and intermolecular forces.
Boiling point is primarily determined by the strength of intermolecular forces. The stronger the intermolecular forces, the higher the boiling point. In the case of ethyl acetate (CH3COOCH2CH3) and methyl acetate (CH3COOCH3), ethyl acetate has a higher boiling point due to stronger intermolecular forces. This is because the ethyl group (-CH2CH3) in ethyl acetate has more electrons and a larger molecular size compared to the methyl group (-CH3) in methyl acetate. The presence of the larger ethyl group leads to stronger London dispersion forces (also known as van der Waals forces) between ethyl acetate molecules, resulting in higher boiling point.
Heat of vaporization is the amount of energy required to convert a substance from liquid to gas at its boiling point. It is related to the strength of intermolecular forces as well. When a substance vaporizes, the intermolecular forces between molecules need to be overcome to allow molecules to transition into the gas phase. Since ethyl acetate has stronger intermolecular forces, more energy is required to break those forces during vaporization compared to methyl acetate. Therefore, ethyl acetate has a higher heat of vaporization than methyl acetate.
In summary, the difference in boiling point and heat of vaporization between ethyl acetate and methyl acetate can be attributed to the variation in molecular structure and the corresponding strength of intermolecular forces, particularly the larger and more polarizable ethyl group in ethyl acetate compared to the smaller methyl group in methyl acetate.