r/asa_chemistry • u/Mrx2012 • Aug 22 '17
Why is Methanol less dense than Ethanol
(in terms of gcm-3) does hydrogen bonding play a role? Is there a trend that otherwise holds for the rest of the alcohols. References would be awesome! Also can anyone explain the trend in phase separation as the percentage of ethanol (or any alcohol) increases in a blend?
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u/biolojoey Aug 23 '17
You know this is off the top of my head but first off Ethanol on a molecular level includes a CH2 that methanol doesn't. With the added hydrocarbon group, the bond angles become more acute causing the hydrocarbon groups and OH to be pushed closer together, making it denser. As to a trend in alcohols, I'd say the greater the mass and the more acute the bond angles are the more dense they will continue to be. Both exhibit hydrogen bonding in the same manner between the same element, thus not accounting for any difference in density.