Effervescence with NaHCO3

How To find which organic compound gives effervescence when reacts with $\ce{NaHCO3}$? Specially in case of phenols, which one reacts and which does not? According to my professor, all acids stronger than $\ce{H2CO3}$ evolve $\ce{CO2}$ when treated with $\ce{NaHCO3}$. But I do not understand how to find which acid is stronger than $\ce{H2CO3}$, further how to find same for $\ce{Na}$ and $\ce{NaOH}$ especially when the pKa values are not given in question.

• You can assume that the phenols are less acidic than $\ce{H2CO3}$. – DHMO Jan 16 '17 at 14:44
• What about substituted phenols like nitro Phenols etc.? – Piyush Raut Jan 16 '17 at 14:45
• Good point. 2,4-dinitrophenol is a stronger acid than $\ce{H2CO3}$. – DHMO Jan 16 '17 at 14:47
• Are there many such compounds that I will have to remember or just few exceptions? – Piyush Raut Jan 16 '17 at 14:48
• What exactly does your question look like? – DHMO Jan 16 '17 at 14:53