Picric acid is obtained by treating phenol first with concentrated sulfuric acid, converting it to phenol-2,4-disulphonic acid, and then with concentrated nitric acid to yield 2,4,6-trinitrophenol. The modern method is preferred for improved yield in the preparation of picric acid.
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Phenol reacts with dilute nitric acid at low temperature, producing a mixture of ortho and para nitrophenols. Steam distillation is used to separate the isomers; o-nitrophenol is steam volatile due to intramolecular hydrogen bonding, while p-nitrophenol is less volatile due ...
The -OH group in phenol activates the benzene ring towards electrophilic substitution and directs incoming groups to ortho and para positions due to the electron-rich nature of these positions caused by resonance effects from the -OH group.
Tertiary alcohols do not undergo oxidation reactions. Under strong conditions (KMnO₄) and elevated temperatures, cleavage of various C-C bonds occurs, leading to a mixture of carboxylic acids with fewer carbon atoms.
PCC is a milder reagent for oxidizing primary alcohols to aldehydes. Secondary alcohols are oxidized to ketones using chromic anhydride (CrO₃).
Dehydrogenation occurs in alcohol oxidation, involving the cleavage of O-H and C-H bonds. Primary alcohols oxidize to aldehydes or carboxylic acids, depending on the oxidizing agent. Strong agents like acidified potassium permanganate yield carboxylic acids directly.
Dehydration of alcohols, leading to the formation of alkenes, occurs with protic acids (e.g., concentrated H₂SO₄ or H₃PO₄) or catalysts like anhydrous zinc chloride or alumina. The relative ease of dehydration follows the order: Tertiary > Secondary > Primary.
Phosphorus tribromide is used to convert alcohols to alkyl bromides. This reaction differs from the Lucas test, offering an alternative method for the transformation of alcohols into halides.
Alcohols react with hydrogen halides to form alkyl halides. The Lucas test, using Lucas reagent (conc. HCl and ZnCl₂), distinguishes between alcohol classes based on the time taken for turbidity to appear; tertiary alcohols show immediate turbidity, while primary alcohols ...
Alkenes undergo acid-catalyzed hydration in the presence of water and acid catalyst, forming alcohols. In the case of unsymmetrical alkenes, the addition follows Markovnikov’s rule.