Disable button in jQuery

Use .prop instead (and clean up your selector string):

function disable(i){
    $("#rbutton_"+i).prop("disabled",true);
}

generated HTML:

<button id="rbutton_1" onclick="disable(1)">Click me</button>
<!-- wrap your onclick in quotes -->

---

But the “best practices” approach is to use JavaScript event binding and this instead:

$('.rbutton').on('click',function() {
    $(this).prop("disabled",true);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<button class="rbutton">Click me</button>