Name Reactions - Carbonyl Compounds (Aldehyde, Ketones and Carboxylic Acid)
Important Name Reactions of Carbonyl Compounds
(a) Rosenmund Reduction: Acid chloride are converted to corresponding aldehydes by catalytic reduction. The reaction is carried out by passing H2 gas through a hot solution of acid chloride in the presence of Pd deposited over BaSO4 (partially poisoned with sulphur or quinoline).
(b) Stephen reaction: Nitriles are reduced to corresponding imines with SnCl2 in the presence of hydrochloric acid, which on hydrolysis give corresponding aldehyde.
(c) Etard reaction: Chromyl chloride oxidises toluene to chromium complex which on hydrolysis gives benzaldehyde.
(d) Gatterman–Koch reaction: When benzene or its derivative is treated with carbon monoxide and hydrogen chloride in the presence of anhydrous AlCl3 and CuCl, it gives benzaldehyde or substituted benzaldehyde.
(e) Friedel–Crafts reactions: Friedel–Crafts alkylation: Benzene and other aromatic compounds react with alkyl halides in the presence of anhydrous AlCl3 to form alkyl benzenes.
Friedel–Crafts acylation: Benzene and other aromatic compounds react with acylchlorides or acid anhydrides in the presence of anhyd. AlCl3 to form aromatic ketone.
(f) Clemmensen reduction: The carbonyl group of aldehydes and ketones is reduced to CH2 group on treatment with zinc amalgam and concentrated hydrochloric acid.
(g) Wolff–Kishner reduction: The carbonyl group of aldehydes and ketones is reduced to —CH2 group on treatment with hydrazine followed by heating with potassium or sodium hydroxide in a high boiling solvent such as ethylene glycol.
(h) Aldol condensation: Two molecules of aldehydes or ketones containing at least one a-hydrogen atom on treatment with dilute alkali undergo condensation to form b-hydroxy aldehydes (aldol) or b-hydroxy ketones (Ketol).
(i) Cross aldol condensation: When aldol condensation is carried out between two different aldehydes and/or ketones, it is called cross aldol condensation.
(j) Cannizzaro reaction: Aldehydes which do not have an α-hydrogen, undergo self-oxidation and reduction (disproportionation) reaction on treatment with concentrated alkali. In this reaction, one molecule of the aldehyde is reduced to alcohol while another is oxidised to carboxylic acid salt.
(k) Hell-Volhard-Zelinsky reaction: Carboxylic acids having an α-hydrogen are halogenated at the a-position on treatment with chlorine, or bromine in the presence of red phosphorus to give α-halocarboxylic acids.
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