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Test to distinguish primary, secondary and tertiary alcohol Oxidation of alcohols involves the formation of a carbon oxygen double bond with the cleavage of an O-H and C-H bonds. The products of oxidizing reaction depends on the nature of alcohols (primary, secondary or tertiary nature of the carbon) and also the oxidizing agent used. Hence this reaction can be utilized for distinguishing the primary, secondary and tertiary alcohols from one another A primary alcohol when treated with potassium to an aldehyde and then to an acid. Both the aldehyde and acid contain the same number of carbon atoms as the parent alcohol. A secondary alcohol on oxidation with acidified K2Cr2O7 or chromium trioxide (CrO3) forms a ketone with the same number of carbon atoms as the parent alcohol. The ketone is further oxidized under strong conditions to form a mixture of acids, each containing lesser number of carbon atoms than the parent alcohol. Tertiary alcohols do not undergo oxidatio...

Alcohols undergo dehydration (removal of a molecule of water) on treating them with protonic acids(conc. H 2 SO 4 or H 3 PO 4 ) or catalysts such as anhydrous zinc chloride or alumina to form alkenes. Ethanol undergoes dehydration to form ethylene by heating it with concentrated H 2 SO 4 at 443 K. C 2 H5OH (ethanol)----(conc.H 2 SO 4 , 443 K)-----> CH 2 = CH 2 (ethylene) + H 2 O Secondary and tertiary alcohols are dehydrated under milder conditions. For example The relative ease of dehydration of alcohols follows the order: Tertiary alcohol > Secondary alcohol > Primary alcohol In the above reaction, if alcohol is in excess acidic dehydration takes place in a different way to yield an ether. The ether is formed by the elimination of one water between molecule from two hydroxyl groups.  Related post Chemical properties of Alcohols and Phenols

Reaction with phosphorus halides and SOCl 2 Alcohols react with phosphorus tri or penta halides or thionyl chloride in pyridine to form the corresponding alkyl halides. 3R - OH + PX 3 --------------> 3R - X + H 3 PO 3 R - OH + PX 5 --------------> R - X + POX 3 + HX R - OH + SOCl 2 -------(pyridine)---------> R - Cl + SO 2 + HCl Alcohols are converted to alkyl bromides by reaction with phosphorus tribromide 3ROH + PBr 3 ---------------> 2RBr + H 3 PO 3 Alkyl iodides are obtained by reacting and alcohol with PI 3 3ROH + PI 3 -------(red p + I 2 )-------> 3RI + H 3 PO 3 3C 2 H 5 OH + PI 3 -------(red p + I 2 )-------> 3C 2 H 5 OH + H 3 PO 3 PBr and PI 3 are obtained in the reaction mixture by the action of red phosphorous and bromine or iodine. Alkyl chlorides are prepared by reacting an alcohol with phosphorus trichloride, phosphorus penta chloride or thionyl chloride. 3R - OH + PCl 3 ----------------> 3R - Cl + H 3 PO 3 3C 2 H 5 ...

Alcohols react with hydrogen halides to give alkylhalides. ROH + HX --------> R-X + H2O The alcohol may be primary, secondary or tertiary and hydrogen halide may be HCl, HBr or HI. For example, CH 3 CH 2 CH 2 OH + HI ------------> CH 3 CH 2 CH 2 I + H 2 O To increase the yield of haloalkane a dehydrating agent like anhydrous ZnCl2 is used to remove the water formed. In this reaction, the reactivity of alcohols decreases in the order tertiary > secondary > primary. Among hydrogen halides reactivity decreases in the order HI > HBr > HCl  Related post Chemical properties of Alcohols and Phenols

The difference in reactivity of primary, secondary and tertiary alcohols with HCl distinguishes them from one another. This test is known as Lucas test. In this method, the alcohol is treated with Lucas reagent (a mixture of conc. HCl and anhydrous ZnCl 2 ). The alcohol is converted into alkyl halides. Alcohols are soluble in Lucas reagent while their halides are insoluble. The formation of alkyl halide is indicated by the appearance of turbidity in the reaction mixture. As the reactivity of alcohols with halogen acids is in the order tertiary > secondary > 2primary, the time required for the appearance of turbidity will be different for primary, secondary and tertiary alcohols which helps to distinguish them from one another. In the case of tertiary alcohols, turbidity is produced immediately at room temperature. Secondary alcohols give turbidity in few minutes while primary alcohols do not produce appreciable turbidity at room temperature, but give turbidity only on heating...

ESTERIFICATION Alcohols and phenols react with carboxylic acids, acid chlorides and acid anhydrides to form esters. R-O-H + R' - COOH -----H+-----> ROCOR' + H 2 O Ethanol Acetic acid Ethyl acetate(Ester) C 2 -OH + CH 3 -COOH -----H 2 SO 4 ----------> C 2 H 5 O COCH 3 + H 2 O Ar-OH + R'-COOH ------------------> ArOCOR' + H 2 O Phenol Ester Ar-OH/ R-OH + (R'CO) 2 ---------H + ----------> Ar/ ROCOR' + R'COOH Anhydride Ease of esterification of alcohol is in the order primary> secondary> tertiary . The reaction with carboxylic acid and acid anhydride is carried out in presence of small amount of concentrated sulphuric acid. The reaction with carboxylic acid is reversible, and therefore, water is removed as soon as it is formed. The Reaction With Acid Chloride Is Carried Out In Presence Of A Base (Pyridine) so as to remove HCl. It also shifts the equilibrium to right hand side. The introduction of acetyl (CH3CO-) ...

Phenols react with aqueous sodium hydroxide to form sodium phenoxides. But alcohols are neutral to this reaction. The above reactions show that alcohols and phenols are acidic in nature. In fact, alcohols and phenols are Bronsted acids, that is they can donate a proton to a strong base (B:) On treating an alkoxide with water the starting alcohol is obtained. This reaction shows that water is a better proton donor than alcohol. In other words, alcohols are weaker acids than water. Also, in the above reaction, we can see that alkoxide ion is a better proton acceptor than hydroxide ion, which shows that alkoxides are stronger bases. For example, sodium ethoxide is a stronger base than sodium hydroxide. The acidic character of alcohols is due to the polar O-H bond. An electron releasing group increases the electron density over the oxygen atom tending to decrease the polarity of O-H bond. This decreases the acid strength of alcohols decreases in the following order. Obvio...