Empirical Formula: C₄H₅N
Molecular Weight: 67.0892 
Structure of Crotononitrile (CAS NO.4786-20-3):
                      
Index of Refraction: 1.417
Density: 0.822 g/cm³
Flash Point: 20 °C
Enthalpy of Vaporization: 35.86 kJ/mol
Boiling Point: 120.5 °C at 760 mmHg
Vapour Pressure: 15.2 mmHg at 25 °C
Storage temp: Flammables area
Appearance: Clear light yellow liquid
 

Carcinogenicity of Crotononitrile (CAS NO.4786-20-3) hasn't been listed as a carcinogen by NTP, IARC,ACGIH, or CA Prop 65. And its toxicological properties have not been fully investigated.You can see actual entry in RTECS for complete information.

Reported in EPA TSCA Inventory.

A poison by ingestion, intravenous, and subcutaneous routes. When heated to decomposition it emits toxic vapors of NO_x and CN⁻.
 

Hazard Codes: FXn
Risk Statements: 11-22-36/37/38-26-16
R11:Highly flammable. 
R16:Explosive when mixed with oxidizing substances. 
R22:Harmful if swallowed. 
R26:Very toxic by inhalation. 
R36/37/38:Irritating to eyes, respiratory system and skin.
Safety Statements: 16-26-36
S16:Keep away from sources of ignition. 
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. 
S36:Wear suitable protective clothing.

 Crotononitrile ,its cas register number is 4786-20-3. It also can be called 2-Butenenitrile ; cis-beta-Methylacrylonitrile ; (E)-2-Butenenitrile ; 2-Butenenitrile, (2E)- and (2E)-But-2-enenitrile . It is hazardous,so the first aid measures and others should be known. Such as: When on the skin: first,should flush skin with plenty of water immediately for at least 15 minutes while removing contaminated clothing. Secondly,Get medical aid. Or in the eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Then get medical aid soon. While ,it's Inhaled: Remove from exposure and move to fresh air immediately.Give artificial respiration while not breathing. When breathing is difficult, give oxygen. And as soon as to get medical aid. Then you have the ingesting of the product : Wash mouth out with water,and get medical aid immediately.Notes to physician: Treat supportively and symptomatically.
In addition, Crotononitrile (CAS NO.4786-20-3) can be stable under normal temperature and pressure conditions.It is not compatible with strong oxidizing agents, and you must not take it with incompatible materials. And also prevent it to broken down into hazardous decomposition products: carbon dioxide, carbon monoxide.