Sciencemadness Discussion Board

alcohols test

morsagh - 24-2-2016 at 13:19

I need test for secondary alcohols but i can´t use KMnO4 because of positive result on double bond, I don´t have chromates, and there is only a little of sample so esterification can´t be used too. Please help me.

gdflp - 24-2-2016 at 13:35

Depending on how sensitive you need the test to be, you could try oxidizing the alcohol with a mild reagent, then using 2,4-DNPH to precipitate the ketone. Won't work if you are expecting the presence of a primary alcohol, ketone, or aldehyde though. Of course, an NMR or IR spectrum would work as well, depending on what facilities you have access to.

alexchim - 24-2-2016 at 14:14

Lucas's reagent, concentrated solution of ZnCl2 in hydrochloric acid. It is used to identify alcohols, in a test tube, R-OH gives no reaction, R1R2C-OH gives a slow formation of milky alkyl chloride, R1R2R3C-OH gives an instantaneous reaction of formation of tertiary alkyl chloride.

Magpie - 24-2-2016 at 15:56

Vogel's 3rd edition (forum library) gives some tests for alcohols. Two of them are: 1) make an acetate w/acetyl chloride, and 2) react with Na to give H2 bubbles.

blogfast25 - 24-2-2016 at 16:37

Quote: Originally posted by Magpie  
2) react with Na to give H2 bubbles.


Surely unless your suspected alcohol is bone dry that's just begging for a false positive?