i posted this already but i got the answer for someone elses question.
the pka of acetone is CH3COCH3 is 19.3 which of these bases is strong enough to deprotonate acetone?
a)KOH (pka of H20 = 15.7)
b)Na+ -C(triplebond)CH (pka of C2H2 = 25)
c)NaHCO3 (pka of H2CO3 = 6.4)
d)NaOCH3 pka of CH3OH = 15.6)
i know the answer is b but why is it b? is it because the pka is high?
Yes, you are correct. The answer is b) Na+ -C≡CH because it has the highest pKa value amongst the given choices. A higher pKa value indicates a weaker acid. Since acetone has a pKa of 19.3, a base with a higher pKa than acetone can deprotonate acetone.
Let's compare the pKa values:
a) KOH: pKa of H2O = 15.7 (lower than acetone's pKa)
b) Na+ -C≡CH: pKa of C2H2 = 25 (higher than acetone's pKa)
c) NaHCO3: pKa of H2CO3 = 6.4 (lower than acetone's pKa)
d) NaOCH3: pKa of CH3OH = 15.6 (lower than acetone's pKa)
Since only the base in answer b) has a higher pKa value than acetone, it is the only strong enough base to deprotonate acetone effectively.
To determine which base is strong enough to deprotonate acetone, you need to compare the pKa values of the potential bases with the pKa value of acetone (19.3). The lower the pKa value of a base, the stronger it is. Therefore, the base should have a pKa lower than 19.3 in order to be strong enough to deprotonate acetone.
Let's compare the pKa values of the potential bases listed:
a) KOH (pKa of H2O = 15.7): This base has a lower pKa than acetone, so it would be strong enough to deprotonate acetone.
b) Na+ -C≡CH (pKa of C2H2 = 25): This base has a higher pKa than acetone, so it would not be strong enough to deprotonate acetone.
c) NaHCO3 (pKa of H2CO3 = 6.4): This base has a much lower pKa than acetone, so it would be strong enough to deprotonate acetone.
d) NaOCH3 (pKa of CH3OH = 15.6): This base has a lower pKa than acetone, so it would be strong enough to deprotonate acetone.
Based on the comparison, option b) Na+ -C≡CH has a pKa higher than acetone, which means it is not strong enough to deprotonate acetone. Therefore, the correct answer is not b) but rather the base with the lowest pKa value, which is a) KOH (pKa of H2O = 15.7).