<link href="//cdn.bootcss.com/select2/3.5.4/select2.min.css" rel="stylesheet"/>

<script src="//cdn.bootcss.com/jquery/1.7.1/jquery.min.js">

</script>

<script src="//cdn.bootcss.com/select2/3.5.4/select2.min.js">

</script>

<p>

    <select id="e18" style="width:50%" class="populate">

    <optgroup label="Alaskan/Hawaiian Time Zone">

        <option value="AK">Alaska</option>

        <option value="HI">Hawaii</option>

    </optgroup>

    <optgroup label="Pacific Time Zone">

        <option value="CA">California</option>

        <option value="NV">Nevada</option>

        <option value="OR">Oregon</option>

        <option value="WA">Washington</option>

    </optgroup>

    </select>

    <br/>

</p>

<p>

    <select multiple="multiple" id="e18_2" style="width:75%" placeholder="Select a state" class="populate placeholder">

    <option></option>

    <optgroup label="Alaskan/Hawaiian Time Zone">

        <option value="AK">Alaska</option>

        <option value="HI">Hawaii</option>

    </optgroup>

    <optgroup label="Pacific Time Zone">

        <option value="CA">California</option>

        <option value="NV">Nevada</option>

        <option value="OR">Oregon</option>

        <option value="WA">Washington</option>

    </optgroup>

    </select>

    <br/>

</p>

<script>

$("#e18,#e18_2").select2();

</script>