How does vitamin C function as a bleaching agent?

Answer 1

That is certainly not a very common use of vitamin C, but basically through redox chemistry. When you bleach something, for example, using commercial bleach, it has sodium hypochlorite which oxidizes "dirt" (whatever is being bleached). Vitamin C is a strong reductant (since it reduces things it's an antioxidant, in case you're wondering about it's very common use), and so it simply reduces "dirt" (or whatever). I have never heard of it being used in bleach before, but I suppose it's hypothetically possible, it would just be far more expensive than the two common components of commercial bleach, sodium hypochlorite and hydrogen peroxide.