preventDefault dont stop submit function

How can I make that preventDefault work, I don’t understand the syntax well, if you can help me thank you very much

The Alerts work but the preventDefault does not stop the process, it just happens as knowing that there is an alias but it does not stop the submission of the form

   $('#submit').on('click', function(e){ 

       
     $.ajax({
    		url: "validar_rut_alias.php",
    		dataType:"json",
    		}).done(function (data) {
			

			$.each(data, function(id, nombre) {
					
					if(nombre.alias==$("#alias").val()){
						alert("alias registered ");
						e.preventDefault();
					}
					else if(nombre.rut==$("#rut").val()){
						alert("rut registered");
						e.preventDefault();
					}
					

			});
			
			
			
			
			
		});

    });