Vitamin c would not replace sorbate but I know some people years ago who thought it might help replace sulfite. Sorbate is used mainly to prevent fermentation while sulfite and ascorbic acid help eat oxygen and reduce the effect oxygen has on wine (sulfite does other things as well)
From what I read years ago, the effect of ascorbic acid don't last long but is very quick to start.
People who were marketing there wine as "organic" sometimes used vitamin c.
It might be acceptable for a wine that is going to be consumer early but not for something you would age, even a little bit.
FYI - a handful of dried apricots have about 10 times more sulfite than a glass of wine. This is a good way of testing whether you have an allergy or not.
