In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Without the knowledge of the medical personnel , the patient ' s mother administered three doses of clonidine during the evening before and morning of surgery to reduce anxiety .
### Output Text:
Without the knowledge of the medical personnel , the patient ' s mother administered three doses of <span class="chemical">clonidine</span> during the evening before and morning of surgery to reduce anxiety . 