Questions dealing with carboxylic acids

1. Propose a sequence of reactions to effect the following conversions:

 

1. 3,5-dinitrobenzoyl chloride from benzene

 



 

2. phenylethanoic acid from toluene

 

  

3. butanoic acid from ethanol



2. Propose a synthesis of CH₃¹³CH₂CO₂H using ¹³CO₂ as source of ¹³C.



3. Tropic acid is isolated from atropine, an alkaloid found in Atropa belladona (deadly nightshade). Its molecular formula is C₉H₁₀O₃. Tropic acid forms bezoic acid on oxidation with hot KMnO₄. Tropic acid also reacts with HBr to form compound "A", C₉H₉O₂Br. Compound "A" reacts with alcoholic KOH to give atropic acid, C₉H₈O₂. Catalytic hydrogenation of atropic acid forms hydratropic acid, C₉H₁₀O₂. Hydratropic acid may be sythesized by treating the Grignard reagent formed from 1-cholor-1-phenylethane with dry ice followed by acid workup.

 

Oxidation of tropic acid to benzoic acid tells us that tropic acid contains a monosubstitued benzene ring. Reaction with HBr removes an "OH" and introduces a "Br". The acid therefore contains an alcohol group. Atropic acid is obtained by dehydrobrominating compound "A" (compare C₉H₈O₂Br with C₉H₈O₂). 

1. What is the structure of hydratropic acid?



2. What is the structure of atropic acid?

 Atropic acid gives hydratropic acid on hydrogenation and so must be:

  

3. What is the structure of compound "A"? 
4. Name compound "A". 

Either 2-bromo-2-phenylpropanoic acid or 3-bromo-2-phenylpropanoic acid 

5. What is the structure of tropic acid? 

Either 2-hydroxy-2-phenylpropanoic acid or 3-hydroxypropanoic acid 

4. Give a structure of compound "X", C₃H₅ClO₂, consistent with the following ¹H NMR data:

 d = 1.73 (3H, doublet), d = 4.47 (1H, quartet), d = 11.22 (1H, singlet).

  2-chloropropanoic acid 

5. Identify the reagents in the following scheme:

 





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Updated August 23, 2002