Question

Ch.22 Reactions at the a-carbon Due: Wednesday, November 6 at the beginning of class Multiple Choice Section (0.5 pt each) 1. (Review) What functional group would the following reaction produce? 4. What is the most acidic hydrogen in the following compound? BC CH,CH,OH H₂o (a) A (b) B CI pyridine HI H D (c) C (d) D (b) ester AH (a) amide (c) anhydride (d) ketone 2. What would be the product of the reaction sequence shown below? 5. (Review) Which of the following represents a pair of keto-enol tautomers? OH SOCI pyridine 1. DIBAL 2. H2O and HO OH and NH2 ☺ and vi 애 and none of these are keto- enol tautomers 3. Amides can be hydrolyzed in the presence of acid and heat to give what functional group as the final product? 6. Which set of conditions should be used to generate a thermodynamic enolate? (a) aldehydes (b) carboxylic acids (c) nitriles (d) imines (e) primary alcohols (a) sodium hydroxide at room temperature (b) t-butoxide at -78 °C (c) LDA at 30 °C (d) NaH at -78 °C

Answer 1

1.

Correct option: b

Acid chloride and alcohol react to form ester.

2.

Correct option: b

Carboxylic acid forms acid chloride on reaction with SOCl₂ in presence of pyridine. Acid chloride reacts with DIBAL and subsequent aqueous work up yields alcohol.

Note: DIBAL reduces acid chloride to aldehyde first. The reaction stops here if the reaction is carried out at low temperature (-78 ^oC). If the reaction is carried out at room temperature then it further reduces aldehyde to alcohol. There is no temperature mentioned here. So room temperature is taken as the reaction temperature.

3.

Correct option: b

Acidic hydrolysis of amide yields carboxylic acids.

4.

Correct option: d

The proton D is most acidic as the carbanion forms on the removal of D proton is stabilized by the C=O as well as C $\equiv$ N via resonance.