Loading Div not showing on Jquery.Show()

was trying to show loading gif and call ajax request (which responds after huge time) and then i hide loading gif.

Below is the code :

$('.loading-gif').show();
$ajax({url:'',async:false}).done(function(){...//some operation});
$('.loading-gif').hide();

I would like to know why this is happening. Note :When i check using debug it works but the gif image stops its animating when ajax request is called. Also what is solution for me to get this resolve.