It would make your freezer run overdrive to remove that much heat, which isn't efficient as far as energy is concerned. Not to mention it just isn't good to over work the freezer like that. It would likely still take hours to chill 5 gallons down to pitching temps. In my opinion, if you don't want to use a chiller you could do an over night "no chill"..
Since it's an empty freezer, next time fill the freezer with as much frozen stuff as possible first while still allowing room for the wort. Bags of ice, or cheaper, frozen water bottles or tupperware, whatever. All that ice will help your freezer work more efficiently (once frozen) and also help the freezer combat the extra heat of hot wort.
I'll just use my wort chiller from now on. I was being lazy and trying to make a slightly less mess in the kitchen today. My dumb ass decided to clean it before I brewed.
What? You destroyed the rampant bacteria by cleaning your kitchen first before brewing! You probably used StarSan to sanitize equipment too. What were you thinking?!