Button text not changing after ajax success changes

I am trying to change button text on button click before sending an AJAX request. The text is not changing until after the AJAX success has run. Why is this happening?

I also tried using the trigger and change functions.

$(function() {
  $("#contactbutton").click(function(e) {
    var $this = $(this);
    $this.text('Submitting....');
    $('#contactbutton').prop('disabled', true);
    e.preventDefault();
    var name = $("#name").val();
    var dataString = 'name=' + name;
    
    $.ajax({
      type: "POST",
      url: "emailsend.php",
      data: dataString,
      success: function() {
        window.open("thankyou.php");
      },
      async: false
    });
    
    return false;
  });
});