Rank the following amides from greatest reactivity to least reactivity toward acid-catalyzed hydrolysis:

Short Answer

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Amide shows avariety of chemical reactions. They are reactive due to the -NH2group. As a result, different nucleophiles can be substituted in the amide.

Nucleophile substitution of hydroxide group in the amide occurs at ahigh temperature, resulting in carboxylic acid formation.

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01

Amide reactivity

Amide shows avariety of chemical reactions. They are reactive due to the -NH2group. As a result, different nucleophiles can be substituted in the amide.

Nucleophile substitution of hydroxide group in the amide occurs at ahigh temperature, resulting in carboxylic acid formation.

02

Comparing amide reactivity

The relative reactivity of the given amides depends on the basicities of their leaving group; that is, the weaker the base, the more reactive the given amide.

  • The given amide (A) on removing the leaving group cyclohexyl ammonium ion has the pKa value of 11.2.
  • The given amide (B) on removing the leaving group anilinium ion has the pKa value of 4.58.
  • The given amide (C) on removing the leaving group para-nitroanilinium ion has the pKa value of 0.98.

The lower the pKa value, the stronger the acidic, the weaker the conjugate base and the weaker the base better is the leaving group making it more reactive amide[S1] . Therefore, the reactivity order of amide is as follows.


Reactivity order of amide

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Most popular questions from this chapter

Name the following:

Question: Draw a structure for each of the following:

a. N,N-dimethylhexanamide

b. 3,3-dimethylhexanamide

c. Cyclohexanecarbonyl chloride

d. Propanenitrile

e. propionamide

f. sodium acetate

g. benzoic anhydride

h. b-valerolactone

i. 3-methylbutanenitrile

j. cycloheptanecarboxylic acid

k. benzoyl chloride

Information about the mechanism of the reaction undergone by a series of substituted benzenes can be obtained by plotting logarithm of the observed rate constant determined at particular pH against the Hammett substituent constantσ for the particular substituent. The σvalue for hydrogen is zero. Electron-donating substituents have negativeσ values; the more strongly electron withdrawing the substituent, the more positiveits s value. The slope of a plot of the logarithm of the rate constant σversusis called theρ (rho) value. The ρvalue for the hydroxide-ion-promoted hydrolysis of a series of meta- and para-substituted ethyl

benzoates is +2.46; theρ value for amide formation for the reaction of a series of meta- and para-substituted anilines with benzoyl chloride is -2.78.

  1. Why doesone set of experiments give a positive role="math" localid="1652525783964" ρvalue, whereas the other set of experiments gives a negativeρ value?
  2. Why were ortho-substituted compounds not included in the experiment?
  3. What do you predict the sign of theρ value to be for the ionization of a series of meta- and para-substituted benzoic acids?

a.Identify the two products obtained from the following reaction:

b. A student carried out the preceding reaction, but stopped it before it was half over, whereupon he isolated the major product. He was surprised to find

that the product he isolated was neither of the products obtained when the reaction was allowed to go to completion. What product did he isolate?

Which is a correct statement?

A. The delocalization energy of an ester is about 18 kcal/mol, and the delocalization energy of an amide is about 10 kcal/mol.

B. The delocalization energy of an ester is about 10 kcal/mol, and the delocalization energy of an amide is about 18 kcal/mol.

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