Obiviously, triethyl orthoformate is more acidic than ethnol.
But when both of them deprononated, the negative charge is on oxygen of triethyl orthoformate, while on carbon of ethnol.
1.According to rules learned from organic chemistry, the negative charge on a more electronegative atom(eg. O) is more stable than on less electronegative atom(eg. C).
2.According to rules that when the conjugate base is more stable, then the conjugate acid is more acidic.
So,we can conclude that triethyl orthoformate is less acidic than ethnol.
Seemingly contradictory? I don't know where am I wrong.