Changing option value with jquery not working

<select id="dd">
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
    <option value="4">4</option>
    <option value="5">5</option>
</select>

//change option to 2; works
$("#dd").find('option[value=2]').attr("selected",true);
$("#dd").find('option[value=2]').attr("selected",false)

//change option to 3; works
$("#dd").find('option[value=3]').attr("selected",true);
$("#dd").find('option[value=3]').attr("selected",false);

//change option back to 2; doesn't work
$("#dd").find('option[value=2]').attr("selected",true);

Changing value to back a value that was set earlier, doesn't work.. Any idea? if I am doing something wrong...