If they require A-level Chemistry and you don't have it you will be rejected more or less categorically - and in the rare exception where you might not be, there is a good chance you would be better off if you had. Such requirements are usually because they will assume without further ado from day one you have studied the entirety of that A-level and understand it to a good level. If you have never understood it, you will be starting the course already behind.
You could look into the option of a foundation year, if it's offered, or alternately into taking a gap year and taking A-level Chemistry, if you would much rather the first course. This would likely allow you to pursue that first option - however if you don't want to take A-level Chemistry and/or don't think you would enjoy/do well in it, then this probably translates to that course as well.