Well, no not likely to work. If your AC unit draws 10 amps @ 120 volts you'll need 100 amps @ 12 volts, PLUS some since no inverter is 100% efficient.

Since presumably, you still want all your other electrical stuff to work, you'd need an alternater capable of putting out 100 amps more than your current one can (OK, I know you aren't using 100% of your alternator's capability now, but you get the idea, I hope).

Now what I've always though might work is to use the same type of system used in propane fired refigerators, but use the waste heat from the cooling system or exhast system instead of propane....

Dave