Question

Problem:D. N. Kursanov, a Russian chemist, proved that the bond that is broken in the hydroxide-ion-promoted hydrolysis of an ester is the acyl C-O bond, rather than the alkyl C-O bond, by studying the hydrolysis

of the following ester under basic conditions:

a. What products contained the label?

b. What product would have contained the label if the alkyl C-O bond had broken?

Short answer

Answer

a.

b.

Step-by-step solution

Isotope labeling

Isotope labeling is the method in which theatom in a chemical compound is replaced by its isotopeexample are as follows:

• Replacing hydrogen with its isotope deuterium
• Replacing ¹⁶O with its isotope ¹⁸O

The isotope labeling method detects which chemical bond breaks when the reaction occurs by determining which atom in the product the labeled isotope is found.

18O  label product

The hydroxide ion promoter hydrolysis of given ester ethyl propionate results in carboxylic acid and alcohol formation.

1. When the isotope-labeled () ester ethyl propionate acyl C-O bond is broken, it results in a butanoic acid (carboxylic acid) formation in which oxygen is labeled (); the structure is shown as follows.

Butanoic acid labeled with ¹⁸O

B.. When the isotope-labeled (¹⁸O ) ester ethyl propionate alkyl C-O bond is broken, resulting in an ethanol (alcohol) formation in which oxygen is labeled ( ¹⁸O ); the structure is shown as follows:

Ethanol labelled with¹⁸O