# Test for diethylether or tertiary alcohol?

What is a simple chemical test to tell the difference between a tertiary alcohol (e.g. 2-methylpropan-2-ol) and an ether (specifically diethylether/ethoxyethane)?

Neither of them can be oxidised by reagents such as potassium dichromate, Tollens reagent or fehlings reagent.

I came up with a test in which a less than stoichiometric amount of ethanoic acid is added and left to react, then some sodium carbonate is added and if there is no effervescence that means an ester has formed hence it must have been the alcohol, otherwise it was probably the ether. However I am unsure about the extent to which this reaction completes and it's simplicity.

• See Lucas' reagent. In general, alcohol contains an $\ce{-OH}$ group, hence it would react with many things that ether would not (alkali metals, for example, though this one would hardly make a good practical test). – Ivan Neretin Jun 1 '16 at 15:42
• The problem with testing for alcohols is that ether normally contains a small amount of water which may otherwise give a false positive for a poorly chosen case. Dry the chemical first with sodium or magnesium sulphate. – Lighthart Jun 1 '16 at 16:41
• Place a sample in a test tube and immerse it in an ice water bath. If it freezes, it is the alcohol. If not, diethyl ether. This nose knows the difference. – user55119 Aug 29 '19 at 2:12

As mentioned in the comments, using Lucas' Reagent is the best option in this case because you're dealing with a tertiary alcohol vs an ether, but let's consider your proposal as well.

In principle, it should work because an ether will not react with ethanoic acid whereas an alcohol would. However, the formation of an ester simply by the addition of ethanoic acid to alcohol is not likely to complete (you generally need a dehydrating acid like $\ce{H2SO4}$ to drive the reaction). In other words, when you put in the bicarbonate you will most likely see effervescence.

If you're thinking of looking for effervescence, using thionyl chloride $\ce{SOCl2}$ might be an option since it will react with the alcohol to give a sulfur dioxide gas and HCl:

$$\ce{R-OH + SOCl2 -> R-Cl + SO2(g) + HCl}$$

You have to make sure the solvent is dry though.

In the specific case of t-Butanol vs diethyl ether, though, you could simply heat the solution slightly to about 40 degrees Celsius. If it boils, then you've got diethyl either. If it doesn't, it's t-Butanol.

Diethyl ether is minimally soluble in water (6 grams per 100), but t-butyl alcohol is completely miscible with water, according to Wikipedia.

Selecting between these two compounds can be made by mixing 5 mL of H2O with 5 mL of the unknown. A single phase means t-butanol; two phases means diethyl ether.