Why is propanol better cleaner than ethanol?

[David Peters]

Why is isopropyl alcohol (propanol) reckoned by many people to be a better general cleaner around the house than the ethyl alcohol (ethanol) which is found in methylated spirits?

Thanks for any info.

David

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FOOTNOTE:

I can add that here in the UK the main type of denatured alcohol we can buy for home use is "methylated spirits" and in the UK this is made up almost entirely of ethyl alcohol.

know that in the US denatured alcohol is not necessarily made of ethyl alcohol. This can lead to confusion about what someone is referring to, so for clarity I can repeat that I am referring to UK meths/ethanol. ]

[Dr_Dickie]

Because you cannot safely drink 2-propanol.

[Ernie]

I strongly suspect that the cleaning power of ethanol vs. propanol depends on the nature of the dirt being removed. While it is an oversimplification, think of dirt as being either water soluble or oil soluble. Ethanol (two carbons and one hydroxyl group) will be more effective in removing water soluble dirt, while propanol (three carbons and one hydroxyl) will be more effective at removing grease (oil like substances). Lighter fuel is very effective at removing grease, but is even is more fire hazard than the alcohols.

Ernie

[Doug Miller]

That is not correct. In the US, "denatured alcohol" is specifically ethanol with small amounts of poisonous additives (usually, but not always, methanol) to render it unfit for beverage use.

[Uncle Al]

The denaturants for ethanol to render it non-drinkable (short of Kitty Dukakis) are crud. Ethanol is rather volatile.

[nightjar]

The additives in household meths seem to affect its value as a cleaner, which, as it is sold as a fuel, is not unreasonable. If you want to use meths as a cleaner, you need to get hold of industrial meths.

Colin Bignell

[Gary Dyrkacz]

Ernie is essentially correct. There are other nuances of chemistry that enter into consideration such as the relative acidity of ethyl alcohol versus iso-propanol and the molecular shape, but the "grease" solubilizing idea is a simple way of representing the why you might use 2-propanol over ethanol. Gary Dyrkacz [e-mail] Radio Control Aircraft/Paintball Physics/Paintball for 40+

[HeyBub]

You can get ethyl alcohol at the liquor store under the brand name "Everclear" (190 proof = 95%+ ethanol).

Or you can steal it from the Biology Department of your local university (they pay about 90 cents a gallon). I've got a gallon left over from my school days - about 40 years ago. I'm letting it "age."

[Gideon]

I have seen 55 gallons of pure grain alcohol shipped to a university engineering department by mistake. The sellers often just assume that any shipment of ethanol to a university is for legitimate medical use and doesn't need to be denatured by law. I'm starting my own university tomorrow.

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HeyBub wrote Or you can steal it from the Biology Department of your local university (they pay about 90 cents a gallon). I've got a gallon left over from my school days - about 40 years ago. I'm letting it "age."

[Derek *]

I have an application involving the removal of self adhesive glue residues from transparent conveyor belts. Meths seems to soften it but not remove it, rubbing with a meths soaked wad just seems to move it about, and after about 2-3 minutes of rubbing it starts to get dirty ending up worse than it started. :(

D- Limonene AKA Orange cleaner, or Label remover works a treat especially applied with a commercial isopropanol impregnated wad.

DG

[David Peters]

I too find that these my bicycle degreaser which is based on extracted orange oils is very good indeed for removing labels and will work when rubbing with meths only smears the adhesive around.

However the orange cleaner seems to leave quite a lot of residue (maybe this is from an additive) but that too can be removed very easily.

[David Peters]

Thanks for the info. Can I ask about what you have written in that paragraph.

Does propanol's "three carbons and one hydroxyl" mean that it is more likely than ethanol (with only two carbons and one hydroxyl) to actually DISSOLVE some types of plastics which I am might be trying to clean?

[Doug Miller]

Don't know about your side of the pond, but over here (US) propanol is normally sold in plastic bottles. I've used 2-propanol to clean a lot of things, and never had it damage any plastic.

IMO your premise is wrong (that a longer-chain moleule is more likely to dissolve plastic than a shorter one). I've also successfully used paint thinner (mineral spirits) to clean various plastics without damage. And I've not observed gasoline to be particularly harmful to plastics either. OTOH, acetone (2-propanone) and MEK (2-butanone) are terribly destructive to many common plastics. IOW, it ain't the length of the chain, but what's attached to it, that does the damage.

[doozer]

It really depends on the plastic and the solvent. Some plastics like polypropylene are almost totaly inert and aren't really attacked by anything. Polystyrene on the other hand is attacked by practically everything (it seems). Essentially this is because there are very few points of attack in polypropylene. It is basically just a long chain of carbons. Polystyrene however has plenty of places to attack. There are other factors that come into play though such as how much cross-linking there is in the polymer.

[rekuci]

In addition to toxicity of denatured alcohol and its higher volatility, from a biological disinfection argument, ethanol has to be more concentrated to be effective against bacteria. Optimal percentage against bacteria is 70%.

Isopropanol is a little more toxic toward bacteria, and it is also a better general cleaner because it has a larger nonpolar part, thus it has a lower surface tension. Optimal against bacteria is only ~50%. It's also supposedly cheaper for non-laboratory use because of taxation of ethanol.

[George E. Cawthon]

Actually, what he stated is generally correct, but ethanol and propanol are very close, so one would probably never see any significant difference.

Of course, what you said is correct also, what is on the end is important, but when comparing two alcohols, the same thing is on the end.

As for plastics, oil has some fairly long chains and it is sold in plastic bottles and oil/gas mixtures certainly don't bother the oil bottle plastics. And then of course, there are plastic gas containers. It would be a pretty lousy plastic that would be bothered by methanol, ethanol, or propanol.

[The Natural Philosopher]

Surprisingy enough, methanol is quite agrresive. Dunno why.

I had a toy plastic plane once, with an engine that ran on methonol/nitromethane/oil mix.

I tried to clean it with petrol...and it dissolved the surface!!!

There is no single simple amswer to which solvent dissolves which plastic.

[Chris Lewis]

According to The Natural Philosopher :

That's for sure. First, there are "polar" and "non-polar" solvents. Alcohols are an example of the former (OH bond), and gasoline/kerosene etc are an example of the latter. What they dissolve _tends_ to be fairly mutually exclusive.

And of course, "curing type" plastics (ie: epoxy resin, polyethylene) are immune to most solvents of either kind.

[clifto]

Styrofoam cups seem to melt with booze in them.

[William]

Except that methanol will dissolve many epoxies. It is rather slow though.....

William...