“What I Learned Today” With Jeff Smith — Ethanol Isn’t The Bad Guy
To illustrate this point, pour straight alcohol (like rubbing alcohol or even Jim Beam) in a Styrofoam cup and let it sit for hours. Nothing will happen. Pour an ounce or two of regular pump gasoline in one of these cups and see what happens. Don’t hold the cup over anything you care about because you will get wet as the fuel will instantaneously melt the Styrofoam.
Toluene is one of the milder aromatics used in pump gasoline. Typical pump gasoline can contain as much as 25-percent (!) aromatics which are these ether-based chemicals. These are generally referred to as BETX – which stands for Benzene, Ethylbenzene, Toluene, and Xylene. These are nasty chemicals and are the real culprits traced to attacking carburetors and fuel systems suffering from corrosion issues.
Class is in. I am your instructor. I have a degree in chemistry and worked in the aerospace industry for 35 years.
The two alcohols that you mention will not cause any change to styrofoam. Aromatics will dissolve styrofoam because the styrofoam chemical structure is made using an aromatic based polymer. A general rule in chemistry is that “like dissolves like” so therefore alcohols will not dissolve the cup but aromatics will.
Short chain alcohols such as methanol, ethanol, butanol, and iso-propyl alcohol (rubbing alcohol) contain Carbon, Hydrogen, and Oxygen atoms. They are HYDROPHILLIC (water seeking) and will bond with water because of the presence of a Oxygen-Hydrogen group (called hydroxyl).
Benzene, Toluene, Xylene, and Ethylbenzene do not contain any ether linkages and are NOT ether-based chemicals. They only contain Carbon and Hydrogen atoms (hydrocarbons) and are HYDROPHOBIC (water rejecting) as
@str12-340 correctly pointed out. Aromatics will not absorb water because they do not contain any hydroxyl group(s).
Water and gasoline do not mix. Water is heavier (denser) than gasoline. Fuel storage tanks, such as the ones used in gas stations, typically have a low area on the bottom of the tank to allow any water entrained in the fuel to settle to the bottom where it can be removed.
Ethanol will mix with gasoline because the hydrocarbon end of the ethanol molecule is compatible even though the hydroxyl end is not.
The hydroxyl end of Ethanol will allow water to be suspended in the gasoline blend and to not drop out to the bottom of the container.
The addition of ethanol to gasoline caused the commonly used fuel hoses and gaskets to swell.
The presence of rust in fuel systems is due to the presence of water and not the presence of aromatics.
I have said enough.
Class dismissed.
