Question

Select all that apply. Which of the following bases are strong enough to deprotonate CH3CH2CH2Câ¡CH (pKa = 25), so that equilibrium favors the products?
a. CH3ONa
b. NaNH2
c. NaH
d. CH3CH2Li
e. H2O
f. NH3

Answer 1

Answer:

b, c, and d.

Explanation:

In an acid-base reaction, the equilibrium favors the weaker acid, thus, to the reaction favors it, the product must be weaker than the acid given. As higher is the value of pKa, as weak is the acid. Thus, the base must form a conjugate acid with pKa > 25.

The values of pKa can be found in equilibrium tables. The salts will dissociate to form the acids, which will gain one proton (H+)

a. CH3ONa -> Conjugate acid CH3OH, pKa = 15.5

b. NaNH2 -> Conjugate acid NH3, pKa = 38

c. NaH -> Conjugate acid H2, pKa = 35

d. CH3CH2Li -> Conjugate acid CH3CH3, pKa = 50

e. H2O -> Conjugate acid H3O+, pKa = -1.7

f. NH3 -> Conjugate acid NH4+, pKa = 9.2

Thus, the ones with pKa > 25 are NH3, H2, and CH3CH3, thus the bases are NaNH2, NaH, and CH3CH2Li.