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Which is more polar: H2O or C4H9OH and CH3OH or C4H9OH?
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Posted by
Lukash Tatarka
Which is more polar: H2O or C4H9OH and CH3OH or C4H9OH?
Water is the most polar. It has an unusually high boiling point for a compound that has such a low molar mass, because of extensive hydrogen bonding (an intermolecular attraction that exists only between hydrogen and very small, highly electronegative atoms (O,N,F). With two hydrogens in each molecule and two lone pairs on each oxygen atom, the water molecule is the ideal candidate for forming an extensive network of particles connected via hydrogen bonded. The hydroxyl groups in butyl alcohol will also form hydrogen bonds, but more than half of the molecule is a non-polar alkyl group which dominates the molecule’s properties. Butyl alcohol is not even soluble in water.
Likewise, methanol is less polar than water (half of the molecule is the non-polar methyl group). But the methyl group is smaller than the butyl group and methanol is soluble in water in all proportions. Therefore, methanol is more polar than butanol.
Water is the most polar. It has an unusually high boiling point for a compound that has such a low molar mass, because of extensive hydrogen bonding (an intermolecular attraction that exists only between hydrogen and very small, highly electronegative atoms (O,N,F). With two hydrogens in each molecule and two lone pairs on each oxygen atom, the water molecule is the ideal candidate for forming an extensive network of particles connected via hydrogen bonded. The hydroxyl groups in butyl alcohol will also form hydrogen bonds, but more than half of the molecule is a non-polar alkyl group which dominates the molecule’s properties. Butyl alcohol is not even soluble in water.
Likewise, methanol is less polar than water (half of the molecule is the non-polar methyl group). But the methyl group is smaller than the butyl group and methanol is soluble in water in all proportions. Therefore, methanol is more polar than butanol.
AS the carbon chain becomes LONGER, the molecule becomes LESS POLAR, and LESS likely to dissolve polar solutes… And the best demonstration of this is to consider the solubilities of alcohols in hexanes. Methyl alcohol is INSOLUBLE in hexanes … here, the ability of the alcohol to hydrogen-bond decreases its interaction with, and solubility in the hydrocarbon solvent. On the other hand, ethyl alcohol is SOLUBLE in hexanes. The longer hydrocarbyl tail of the alcohol allows interaction with the non-polar solvent, even tho’ it has an hydroxyl cap…
And clearly, water is more polar than butyl alcohol, and methyl alcohol is more polar than butyl alcohol…
AS the carbon chain becomes LONGER, the molecule becomes LESS POLAR, and LESS likely to dissolve polar solutes… And the best demonstration of this is to consider the solubilities of alcohols in hexanes. Methyl alcohol is INSOLUBLE in hexanes … here, the ability of the alcohol to hydrogen-bond decreases its interaction with, and solubility in the hydrocarbon solvent. On the other hand, ethyl alcohol is SOLUBLE in hexanes. The longer hydrocarbyl tail of the alcohol allows interaction with the non-polar solvent, even tho’ it has an hydroxyl cap…
And clearly, water is more polar than butyl alcohol, and methyl alcohol is more polar than butyl alcohol…
Water is the most polar. It has an unusually high boiling point for a compound that has such a low molar mass, because of extensive hydrogen bonding (an intermolecular attraction that exists only between hydrogen and very small, highly electronegative atoms (O,N,F). With two hydrogens in each molecule and two lone pairs on each oxygen atom, the water molecule is the ideal candidate for forming an extensive network of particles connected via hydrogen bonded. The hydroxyl groups in butyl alcohol will also form hydrogen bonds, but more than half of the molecule is a non-polar alkyl group which dominates the molecule’s properties. Butyl alcohol is not even soluble in water.
Likewise, methanol is less polar than water (half of the molecule is the non-polar methyl group). But the methyl group is smaller than the butyl group and methanol is soluble in water in all proportions. Therefore, methanol is more polar than butanol.
Water is the most polar. It has an unusually high boiling point for a compound that has such a low molar mass, because of extensive hydrogen bonding (an intermolecular attraction that exists only between hydrogen and very small, highly electronegative atoms (O,N,F). With two hydrogens in each molecule and two lone pairs on each oxygen atom, the water molecule is the ideal candidate for forming an extensive network of particles connected via hydrogen bonded. The hydroxyl groups in butyl alcohol will also form hydrogen bonds, but more than half of the molecule is a non-polar alkyl group which dominates the molecule’s properties. Butyl alcohol is not even soluble in water.
Likewise, methanol is less polar than water (half of the molecule is the non-polar methyl group). But the methyl group is smaller than the butyl group and methanol is soluble in water in all proportions. Therefore, methanol is more polar than butanol.
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AS the carbon chain becomes LONGER, the molecule becomes LESS POLAR, and LESS likely to dissolve polar solutes… And the best demonstration of this is to consider the solubilities of alcohols in hexanes. Methyl alcohol is INSOLUBLE in hexanes … here, the ability of the alcohol to hydrogen-bond decreases its interaction with, and solubility in the hydrocarbon solvent. On the other hand, ethyl alcohol is SOLUBLE in hexanes. The longer hydrocarbyl tail of the alcohol allows interaction with the non-polar solvent, even tho’ it has an hydroxyl cap…
And clearly, water is more polar than butyl alcohol, and methyl alcohol is more polar than butyl alcohol…
AS the carbon chain becomes LONGER, the molecule becomes LESS POLAR, and LESS likely to dissolve polar solutes… And the best demonstration of this is to consider the solubilities of alcohols in hexanes. Methyl alcohol is INSOLUBLE in hexanes … here, the ability of the alcohol to hydrogen-bond decreases its interaction with, and solubility in the hydrocarbon solvent. On the other hand, ethyl alcohol is SOLUBLE in hexanes. The longer hydrocarbyl tail of the alcohol allows interaction with the non-polar solvent, even tho’ it has an hydroxyl cap…
And clearly, water is more polar than butyl alcohol, and methyl alcohol is more polar than butyl alcohol…
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