Question

For the following reaction, the products are favored at equilibrium. Classify each of the reactants and products based on their strength as Bronsted Lowry acids or bases.
(C2H5)2NH + C6H5OH -> (C2H5)2NH2+ + C6H5O-

(C2H5)2NH

C2H5)2NH2

C6H5O-

C6H5OH

Match with the following.

a. Stronger Bronsted Lowry acid
b. Weaker Bronsted Lowry acid
c. Stronger Bronsted Lowry base
d. Weaker Bronsted Lowry base

Answer 1

Answer:

(C2H5)2NH    -------------> c. Stronger Bronsted Lowry base

C2H5)2NH2+  ------------>  b. Weaker Bronsted Lowry acid

C6H5O-          ------------->  d. Weaker Bronsted Lowry base

C6H5OH       --------------->   a. Stronger Bronsted Lowry acid

Explanation:

Bronsted-Lowry defined an acid as a molecule or ion which donates a proton, while a base is a molecule or ion which accepts the proton. Bronsted-Lowry Theory of definition of an acid and base could also be extended to include acid-base titrations in non aqueous solution. In this theory, the reaction of an acid with a base constitutes the transfer of a proton from an acid to the base.

From the question given, we are to Classify each of the reactants and products based on their strength as Bronsted Lowry acids or bases:

(C2H5)2NH + C6H5OH    ⇄  (C2H5)2NH2+ + C6H5O-

(C2H5)2NH    -------------> c. Stronger Bronsted Lowry base

C2H5)2NH2+  ------------>  b. Weaker Bronsted Lowry acid

C6H5O-          ------------->  d. Weaker Bronsted Lowry base

C6H5OH       --------------->   a. Stronger Bronsted Lowry acid

In the forward reaction, Phenol (C6H5OH) donates a proton to diethylamine (C2H5)2NH which accepts it. The phenol behaves as an acid and the diethylamine behaves as a base.

In the backward reaction, diethylammonium(C2H5)2NH2+) ion donates a proton to the phenolate (C6H5O-), Therefore, diethylammonium behaving as an acid (proton donor) and the phenolate behaves as a base(proton acceptor)

The equilibrium of this reaction lies to the far right (which is indicated by the longer arrow of the forward reaction) because Phenol is a stronger Bronsted Lowry acid than the diethylammonium. (i.e Weaker Bronsted Lowry acid).

Similarly, the diethylamine is a stronger Bronsted Lowry base while the phenolate which is a weaker Bronsted Lowry base.