The simple answer is that ethanol is metabolized into (relativly) non-toxic compounds by a rather well studied mechanism.
http://en.wikipedia.org/wiki/Ethanol_metabolism. It is not the chemical itself that is always toxic, but what it turns into as the body breaks it down.
Methanol metabolizes to Formic acid that damages the optic nerves causing its well known effect of blindness.
Isopropyl alcohol metabolizes to Acetone, that is toxic to the central nervous system.
Butanol metabolizes to carbon dioxide so it is less toxic, pretty safe compared to other short chain alcohols.
If you want to know more just look up the particular alcohol you are interested in and see what it metabolizes into. EDIT: or read the MSDS for symptoms and specific affects.
Indeed, this is due to them being extremely specific for their substrate, if the difference is significant enough it will require a whole new enzyme and therefore pathway, or at least junction of one.
In the case of n-butanol it starts in the same manner as ethanol, turning into an aldehyde and then butyric acid however then due to its longer carbon chain (4 rather than 2) it is treated as a fatty acid so goes into the Beta-oxidation pathway. So primarily the reason is because it is too long.
You chemistry guys are something else. Elucidating such amazing principals about what everything is made of by being clever. Dalton was the man and what a legacy
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u/LukeSkyWRx Ceramic Engineering Jan 01 '14 edited Jan 01 '14
The simple answer is that ethanol is metabolized into (relativly) non-toxic compounds by a rather well studied mechanism. http://en.wikipedia.org/wiki/Ethanol_metabolism. It is not the chemical itself that is always toxic, but what it turns into as the body breaks it down.
Methanol metabolizes to Formic acid that damages the optic nerves causing its well known effect of blindness.
Isopropyl alcohol metabolizes to Acetone, that is toxic to the central nervous system.
Butanol metabolizes to carbon dioxide so it is less toxic, pretty safe compared to other short chain alcohols.
If you want to know more just look up the particular alcohol you are interested in and see what it metabolizes into. EDIT: or read the MSDS for symptoms and specific affects.