1. Lucas test. This test is based on the difference in the three types of alcohols (having 6 or less carbon) towards Lucas reagent (a mixture of conc. hydrochloric acid and anhydrous zinc chloride) at room temperature.
\(R_3COH+HCl \xrightarrow {ZnCl_2}R_3C.Cl+H_2O\)
Since alkyl halides are insoluble, their formation is indicated by the appearance of a turbidity in the reaction mixture.
The order of reactivity is tert. > sec.> pri.
(i) The tertiary alcohols produce turbidity immediately,
(ii) The secondary alcohols give turbidity within 5-10 minutes.
(iii) The primary alcohols do not give turbidity at all, at room temperature.
2. Action of reduced copper at 300°C: Discussed earlier.
(i) Primary alcohols undergo dehydrogenation to form aldehydes.
(ii) Secondary alcohols undergo dehydrogenation to form ketones.
(iii) Tertiary alcohols undergo dehydration to form olefins.
3. Oxidation test. Discussed earlier.
4. Victor Meyer test. This test is based on the different behaviour of primary, secondary and tertiary nitroalkanes towards nitrous acid. The test involves the following steps.
(a) Alcohol is treated with concentrated hydriodic acid or red phosphorus and iodine to form the corresponding alkyl iodide.
(b) Alkyl iodide is reacted with silver nitrite to form the corresponding nitroalkane.
(c) The nitroalkane is treated with nitrous acid (NaNO2 + H2SO4) followed by treatement with alkali (NaOH or KOH). Upon such treatement different alcohols give different colours.
(i) Primary alcohols produce a blood red colour due to the formation of salt of nitrolic acid.
(ii) Secondary alcohols produce a blue colour due to the formation of pseudonitrole.
(iii) Tertiary alcohols produce no colour. They even do not react with HONO.
5. Esterification.
Since the rate of esterification follows the order:
pri > sec. > ter; the percentage of ester produced from primary, sec. and ter. alcohols with acetic acid are 45-7%, 5-4% and 1-4% respectively.
In the esterification process, the water formed is removed by Dean and Stark apparatus. It should be noted that bulkier the acid or alcohol, slower is the rate (due to steric hindrance). Decreasing order of rate of reaction of different alcohols and acids is
CH3OH > C2H5OH >n-C3H7OH> (CH3)2 CHOH> (CH3)3.COH
HCOOH > CH3COOH > n-C3H/COOH > (CH3)2 CHCOOH (CH3)3CCOOH
