How do you distinguish between primary and secondary alcohols?

Question

Ruby Allen · Accepted Answer

By victor mayer method,
Treat the alcohol with the following reagents in order-
1.P/I2
2.AgNO2
3.HNO2
4.KOH

Christian Anderson · Answer

I would use the Lucas test to distinguish between a primary and a secondary alcohol.

The Lucas test differentiates between primary and secondary alcohols. It is based on the difference in reactivity of the alcohols with #"HCl"# in an #"S"_"N"1# reaction: #"ROH + HCl" → "RCl" + "H"_2"O"# It works because secondary carbocations are more stable and form faster than primary carbocations. The Lucas reagent is an equimolar mixture of #"ZnCl"_2# and #"HCl"#. You add a few drops of your alcohol to the reagent in a test tube A secondary alcohol will react within 3 min to 5 min to form the alkyl halide, which is insoluble and forms an oily layer. #underbrace("CH"_3"CH"_2"CH"_2"CH(OH)CH"_3)_color(red)("pentan-2-ol") + "HCl" stackrelcolor(blue)("ZnCl"_2, "HCl"color(white)(mm))(→) underbrace("CH"_3"CH"_2"CH"_2"CHClCH"_3)_color(red)("2-chloropentane") + "H"_2"O"# A primary alcohol does not noticeably react with Lucas reagent at room temperature. #underbrace("CH"_3"CH"_2"CH"_2"CH"_2"CH"_2"OH")_color(red)("pentan-1-ol") + "HCl" stackrelcolor(blue)("ZnCl"_2, "HCl"color(white)(mm))(→) "No reaction"#

Addison Armstrong · Answer

undefined Primary alcohols have the hydroxyl group (-OH) attached to a carbon atom that is bonded to only one other carbon atom. Secondary alcohols have the hydroxyl group attached to a carbon atom that is bonded to two other carbon atoms.