Chemical/Physical Properties
The boiling point for alcohols is generally high (especially when compared to alkanes with the same carbon chains). For instance, methane has around a -258 degree (F) boiling point compared to methanol's about 148 degree (F) boiling point. This is primarily due to the intermolecular forces of alcohols when compared to alkanes. The -OH groups are polar and have hydrogen bonding intermolecular forces, which is the strongest intermolecular force. These strong forces makes it require more energy to break the intermolecular forces (boiling point) that are attracting the molecules together. As you add carbons, the boiling point increases as the London dispersion forces increases, making it require more energy to break the intermolecular forces between the molecules (boiling point).
The boiling point for phenols is generally high (especially when compared to benzene and alcohols). This is primarily due to the intermolecular forces of phenols and the effect of the oxygen's lone pairs. The -OH groups are polar and have hydrogen bonding intermolecular forces, which is the strongest intermolecular force. These strong forces makes it require more energy to break the intermolecular forces (boiling point) that are attracting the molecules together. The reason it has a higher boiling point to benzene is due to this reason, along with the higher electron density (the lone pairs from the oxygen contributing to the delocalized electrons) increasing the London dispersion forces. Compared to alcohols, the increased ability to pack together due to the cyclic (benzoic) structure makes it have a higher boiling point than alcohols.
The boiling point for thiols is generally low (especially when compared to alcohols and phenols). This is primarily due to the intermolecular forces of thiols when compared to alcohols and phenols. The -SH groups are polar and have hydrogen bonding intermolecular forces, which is the strongest intermolecular force; however, with sulfur they are not nearly as strong as the -OH hydrogen bonding forces. These weaker (yet still strong) forces makes it require more energy to break the intermolecular forces (boiling point) that are attracting the molecules together when compared to alkanes/alkenes/alkynes, but less than alcohols and phenols.
The melting point for alcohols is decently high (especially when compared to alkanes with the same carbon chains). This is primarily due to the intermolecular forces of alcohols when compared to alkanes. The -OH groups are polar and have hydrogen bonding intermolecular forces, which is the strongest intermolecular force. These strong forces makes it more energy to break the intermolecular forces (melting point) that are attracting the molecules together.
The melting point for phenol is generally very high (especially when compared to alkanes and alcohols) and is around 104.9 degrees (F). This is primarily due to the intermolecular forces of phenols when compared to alcohols/alkanes. The -OH groups are polar and have hydrogen bonding intermolecular forces, which is the strongest intermolecular force. These strong forces makes it require more energy to break the intermolecular forces (melting point) that are attracting the molecules together. The reason it has a higher melting point compared to benzene and alcohols is due to this reason, along with the higher electron density (the lone pairs from the oxygen contributing to the delocalized electrons) increasing the London dispersion forces. Compared to alcohols, the increased ability to pack together due to the cyclic (benzoic) structure makes it have a higher melting point than alcohols.
The melting point for thiols is generally low (especially when compared to alcohols and phenols). This is primarily due to the intermolecular forces of alcohols when compared to alcohols and phenols. The -OH groups are polar and have hydrogen bonding intermolecular forces, which is the strongest intermolecular force; however, with sulfur they are not nearly as strong as the -OH hydrogen bonding forces. These weaker (yet still strong) forces makes it require more energy to break the intermolecular forces (melting point) that are attracting the molecules together when compared to alkanes/alkenes/alkynes, but less than alcohols and phenols.
Since solubility is based on the similarities in intermolecular forces of the solute and the solvent, alcohols are gerneally soluble in water. This is due to water having LDF, Dipole-Dipole, and Hydrogen Bonding intermolecular forces, and alcohols having the same intermolecular forces. In terms of solubility with other alcohols, they are soluble. This is due to alcohols sharing the same intermolecular forces of LDF (only). As more carbons are added to the chain of an alcohol, it slowly starts to become insoluble due to the molecules being less packed together as the size and mass increases.
Since solubility is based on the similarities in intermolecular forces of the solute and the solvent, phenols are partially soluble in water. This is due to water having LDF, Dipole-Dipole, and Hydrogen Bonding intermolecular forces, and phenol having the same intermolecular forces. In terms of solubility with other phenols, they are soluble. This is due to phenols sharing the same intermolecular forces of LDF (only). As more carbons are added to the chain of a phenol, it slowly starts to become insoluble due to the molecules being less packed together as the size and mass increases. Along with this, the partial solubility is also due to the phenyl group attached to the -OH which is very stable, making phenol usually only partially soluble in water.
Since solubility is based on the similarities in intermolecular forces of the solute and the solvent, thiols are gerneally considered insoluble in water. This is due to water having LDF, Dipole-Dipole, and Hydrogen Bonding intermolecular forces, and thiols having the same intermolecular forces but a very weak hydrogen bonding force (due to the sulfur), resulting in low solubility with water. In terms of solubility with other thiols, they are soluble. This is due to thiols sharing the same intermolecular forces of LDF (only). As more carbons are added to the chain of an alcohol, it slowly starts to become insoluble due to the molecules being less packed together as the size and mass increases.
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