The structure of ascrobyl palmitate contains a vinyl group, so I assume the red proton would be:
$\begingroup$
$\endgroup$
-
1$\begingroup$ What about the other OH group on the other side of the double bond? $\endgroup$ – orthocresol♦ Mar 19 '17 at 18:52
$\begingroup$
$\endgroup$
The other H (hydrogen) will be more acidic. The ascorbate anion is stabilized by electron delocalization, as I have show below in terms of resonance between two canonical forms.
