Event when a multi-select is deselected

The problem is that I want to run an AJAX with the variable id_company, ONLY when an option of a multiselect is deselected, but I really do not know how to do it. Everything works fine until the condition is out of the event, that's where my AJAX should be. Here is my code below:

$('#select_empresas').on('change',function(e) {
        //if($(this).prop("selected",false)){
        var id_usuario = <?=$userID?>;
        var id_empresa = 0;
        $(this).find("option").each(function(i, v) { 
            if (!$(v).is(":selected") && $.inArray($(v).val(), empresas) >= 0) {
              id_empresa = $(v).val();
              var i = empresas.indexOf($(v).val());
              if(i != -1) {
                empresas.splice(i, 1);
              }
              } else if ($(v).is(":selected") && $.inArray($(v).val(), empresas) < 0) {
                empresas.push($(v).val());
                id_empresa = $(v).val();
              }
        }); 

        //if an option is deselected, execute the code below
        if($(this).find('option').filter(':selected:last').prop("checked")==false){
          console.log(id_empresa);
          /*******
            Code...
          ********/
        }
});

The problem is that I'm using the Materialize framework, and it generates a multi-select like this:

I hope and you can help me, thanks.