0210-Ch18-30 - Reaction with H2O - Nitriles The cyano group...

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Reaction with H 2 O - Nitriles The cyano group is hydrolyzed in aqueous acid to a carboxylic acid and the ammonium ion : Acid-promoted hydrolysis . Ch-18 1 Ph CH 2 C N 2H 2 O H 2 SO 4 H 2 O Ph CH 2 COH O NH 4 + HSO 4 -    Ammonium hydrogen sulfate Phenylacetic acid Phenylacetonitrile + he at + + R-C N H 2 O H + NH OH R-C R-C-NH 2 O     An imidic acid (enol of an amide) + An amide Step 1 : Protonation of the cyano nitrogen gives a cation. Step 2 : The cation reacts with water to give an imidic acid . Step 3 : Keto-enol tautomerism gives the amide. Problem : Draw the detailed mechanism.
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Reaction with H 2 O - Nitriles Hydrolysis of a cyano group in aqueous base gives a carboxylate anion and ammonia (several steps): Base-promoted hydrolysis . Acidification converts the carboxylate anion into the carboxylic acid; ammonia is transformed into ammonium ion. Ch-18 2 CH 3 ( CH 2 ) 9 C N NaOH, H 2 O O CH 3 ( CH 2 ) 9 COH CH 3 ( CH 2 ) 9 CO - Na + O HCl H 2 O NaCl NH 3 NH 4 Cl Sodium undecanoate  Undecanenitrile + heat Undecanoic acid + + Problem : Draw the detailed mechanism.
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Reaction with H 2 O - Nitriles Hydrolysis of nitriles is a valuable route to carboxylic acids. Ch-18 3 CHO HCN, KCN CN OH H 2 SO 4 , H 2 O COOH OH heat Benzaldehyde Benzaldehyde cyanohydrin (Mandelonitrile) (racemic) 2-Hydroxyphenylacetic acid (Mandelic acid) (racemic) ethanol, water CH 3 ( CH 2 ) 8 CH 2 Cl KCN H 2 SO 4 , H 2 O CH 3 ( CH 2 ) 9 COH heat ethanol,   water O CH 3 ( CH 2 ) 9 C N 1-Chlorodecane Undecanenitrile Undecanoic acid
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Reaction with Alcohols - Esters Acid halides react with alcohols to give esters . Acid halides are reactive toward even weak nucleophiles such as water or alcohols, and no catalyst is necessary. Commonly, the reaction is carried out in the presence of a 3° amine both as a catalyst (e.g., pyridine) and as a base that neutralizes HCl formed in the course of the reaction (e.g., pyridine, Et 3 N) . Ch-18 4  Butanoyl chloride Cyclohexyl butanoate + Cyclohexanol HO HCl Cl O + O O Problem : Draw the mechanism (a) without and (b) with a 3° amine as the catalyst and base.
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Reaction with Alcohols - Esters Sulfonic acid esters are prepared by the reaction of an alkane- or arenesulfonyl chloride with an alcohol or phenol The key point here is that OH (a poor leaving group) is transformed into a sulfonic ester (a good leaving group) with retention of configuration at the chiral center.
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This note was uploaded on 04/17/2011 for the course ENY 3005 taught by Professor Staff during the Fall '08 term at University of Florida.

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0210-Ch18-30 - Reaction with H2O - Nitriles The cyano group...

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