Thursday, December 12, 2019

Organic Chemistry for Molecular Mass-

Question: Discuss about theOrganic Chemistry for Molecular Mass. Answer: The boiling point of Hexanal is 126.9 oC while the boiling point of 1-heptanol is 178.5 0C (Haynes, 2014). 1-heptanol has a higher boiling point than hexanal. The difference in the boiling points can be explained in terms of the molecular structures of the two compounds and the nature of the intermolecular forces of attraction between the molecules. The molecular formula of Hexanal is C6H12O and its molecular mass is 100.16 g/mol (Haynes, 2014). The molecular formula of 1-heptanol is C7H16O and its molecular mass is 116.20 g/mol. The structures are as shown below. In 1-Heptanol, the oxygen atom is directly bonded to a hydrogen atom. Since oxygen is highly electronegative, the O-H bond is very polar; with the oxygen end acquiring a partial negative charge and the H end being partially positive. The oxygen atom of one molecule attracts the Hydrogen molecule of a neighboring molecule leading to formation of Hydrogen bonding between the molecules. Hydrogen bonds are the strongest inter-molecular forces and require a lot of energy to overcome hence the unusually high boiling point of 1-heptanol. In Hexanal, the Oxygen atom is not bonded directly to a hydrogen atom hence no hydrogen bonding between molecules. The oxygen atom forms a double bond with carbon. Since O is more electronegative than C, the O=C bond is highly polar, with the Oxygen end acquiring a partial negative charge and the Carbon end a partial positive charge thus, forming a permanent dipole. The dipole of one molecule attracts the oppositely charged end of another molecule leading to formation of dipole-dipole attractions between molecules. The dipole-dipole forces are relatively strong, giving hexanal a significantly higher boiling point compared to other organic molecules of the comparable mass. However, these forces are not as strong as hydrogen bonds and thus explain why the boiling point of hexanal is lower than that of 1-heptanol. References Haynes,W.M. (2014). CRC handbook of chemistry and physics. Boca Raton, FL: CRC Press.

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