removeClass not working

removeClass not working

Hi,
i am trying to reverse an animation using removeclass and it does not work. As I'm quite new to jquery I suppose I am missing something obvious - maybe someone can help.

There is this small window

<div class="fenster f15">
            <div class="flap">
      </div>
      <a href=" http://whatever..."><img class="button" src="button.jpg"/></a>
</div>

which is opend by
      
 $('.fenster').click(function(){
            $(this).addClass("opend");
            $(this).children(".flap").addClass("flap_open" );
            $(this).find(".button").show();
        });

where "flap_open" is my animation
but when I try

$('.flap_open').click(function(){
            $(this).parent(".fenster").removeClass("opend");
            $(this).find(".flap").removeClass("flap_open" );
            $(this).find(".flap").addClass("flap_close" );
            $(this).find(".button").hide();
        });

to trigger the closing animation but nothing happens. I tried as well making a specialiced close button, but that has no effect as well.
any ideas where I made the mistake?