IUPAC Name: N-(2,6-dichlorophenyl)-4,5-dihydro-1H-imidazol-2-amine hydrochloride 
Empirical Formula: C₉H₁₀Cl₃N₃
Molecular Weight: 266.5548g/mol
EINECS: 224-121-5 
Structure of Clonidine hydrochloride (CAS NO.4205-91-8):

Flash Point: 146.9 °C
Enthalpy of Vaporization: 56.09 kJ/mol 
Melting Point: 312 °C
Boiling Point: 319.3 °C at 760 mmHg
Vapour Pressure: 0.000342 mmHg at 25°C 
solubility: H₂O: 50 mg/mL, clear, colorless
Product Categories: Adrenoceptor 
Canonical SMILES: C1CN=C(N1)NC2=C(C=CC=C2Cl)Cl.Cl
InChI: InChI=1S/C9H9Cl2N3.ClH/c10-6-2-1-3-7(11)8(6)14-9-12-4-5-13-9;/h1-3H,4-5H2,(H2,12,13,14);1H
InChIKey: ZNIFSRGNXRYGHF-UHFFFAOYSA-N

 Clonidine has been prescribed historically as an antihypertensive agent. It has found new uses, including treatment of some types of neuropathic pain, opioid detoxification, sleep hyperhidrosis, anaesthetic use, and off-label, to counter the side effects of stimulant medications such as methylphenidate or amphetamine. It is becoming a more accepted treatment for insomnia, as well as for relief of menopausal symptoms. Clonidine(4205-91-8) is increasingly used in conjunction with stimulants to treat attention-deficit hyperactivity disorder (ADHD), for which it is administered in late afternoon or evening for sleep, and because it sometimes helps moderate ADHD-associated impulsive and oppositional behavior, and may reduce tics. Clonidine(4205-91-8) can be used in the treatment of Tourette syndrome. Clonidine(4205-91-8) is also a mild sedative, and can be used as premedication before surgery or procedures.

Poison by ingestion, subcutaneous, intravenous, and intraperitoneal routes. Human systemic effects by ingestion: coma, effects on sleep, fall in blood pressure, gastrointestinal system effects, increase in pulse rate, pulse rate decrease, reduced blood pressure, respiratory depression, respiratory system effects, somnolence. An experimental teratogen. Other experimental reproductive effects. When heated to decomposition it emits toxic fumes of NO_x and Cl⁻.
Hazard Codes: T+
Risk Statements: 25-26 
R25 :Toxic if swallowed. 
R26:Very toxic by inhalation.
Safety Statements: 22-26-28-36/37/39-45 
S22:Do not breathe dust. 
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. 
S28:After contact with skin, wash immediately with plenty of soap-suds. 
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection. 
S45:In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)
RIDADR: UN 2811 6.1/PG 1
WGK Germany: 3
RTECS: NJ2490000
F: 10
HazardClass: 6.1(b)
PackingGroup: III

  Clonidine hydrochloride , its cas register number is 4205-91-8. It also can be called 2-((2,6-Dichlorophenyl)amino)-2-imidazoline hydrochloride ; Apo-Clonidine ; Benzenamine, 2,6-dichloro-N-2-imidazolidinylidene-, hydrochloride ; Capresin ;
 Catapresan ; Chlophazolin ; Clonidine HCl ; Clonidine hydrochloride ; Clonidine monohydrochloride ; Dixarit ; Edolglau ;
 Ipotensium ; Katapresan ; Normopresan ; Novo-Clonidine ; Nu-Clonidine ; Trialox .