If you mix vinegar and Dawn dish soap together, what happens is, it slightly lowers the degreasing power of the Dawn Dish Soap.
Although mixing vinegar and Dawn Dish Soap does create a safe and also still highly effective household cleaner, which still excels at cutting through hard water stains, soap scum and surface grime.
It's mainly through a strictly chemical standpoint that the mixture of Dawn dish soap and vinegar slightly lowers the degreasing power of the dish soap, but it will still work very effectively.
Plain white vinegar is highly acidic with a pH of around 2.4, while standard blue Dawn Dish Soap is slightly alkaline or neutral (pH around 7 to 9).
Mixing the Dawn Dish Soap and Vinegar brings the overall pH closer together.
Also the acid in the vinegar interacts with the anionic surfactants, which are the cleaning molecules in the Dawn Dish Soap.
This prevents the soap from forming what is called "micelles", which are the microscopic structures that trap and lift heavy grease.
And because of this, the mixture is actually less effective at degreasing oily pots and pans than pure Dawn Dish Soap alone.
Although there are no hazards or hazardous fumes when mixing Dawn Dish Soap with vinegar, like there is with bleach and vinegar, which creates deadly chlorine gas, but mixing vinegar and Dawn Dish Soap is completely non toxic and safe to breathe.
And despite the Dawn Dish Soap's grease cutting power being reduced when mixed with vinegar, the combination of vinegar and Dawn Dish Soap works great for bathroom and tile cleaning.