Reported in EPA TSCA Inventory.

The IUPAC name of C.I. Basic Orange 21 is 1,3,3-trimethyl-2-[(E)-2-(2-methyl-1H-indol-3-yl)ethenyl]indol-1-ium chloride . With the CAS registry number 3056-93-7, it is also named as Aizen Cathilon Orange GL ; Aizen Cathilon Orange GLH ; Astrazon Orange ; C.I. 48035 ; Cationic Orange ZH ; Genacryl Orange G ; Nabor Orange G ; Sandocryl Orange B-G ; Sevron Orange G ; 1H-Indole, 2,3-dihydro-1,3,3-trimethyl-2-((2-methyl-3H-indol-3-ylidene)ethylidene)-, monohydrochloride .

The C.I. Basic Orange 21 is slightly soluble in cold water and soluble in hot water. When heated to decomposition it emits toxic vapors of NO_x, HCl, and Cl⁻.  It can be used as metachromatic dye. This product is harmful by inhalation, in contact with skin and if swallowed. It is irritating to eyes, respiratory system and skin. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. After contact with skin, wash immediately with plenty of soap-suds. If you want to contact this product, you must wear suitable protective clothing, gloves and eye/face protection. In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)  

The C.I. Basic Orange 21 can be obtained by the ω-aldehyde and 2-methyl indole as the raw material. They are condensation in the presence of hydrochloric acid , and then dump into the water and change into chloride. After filtered, dried, crushed, we can get the product.

The other characteristics of this product can be summarized as: (1)H-Bond Donor: 1 ; (2)H-Bond Acceptor: 1 ; (3)Rotatable Bond Count: 2 ; (4)Exact Mass: 350.154976 ; (5)MonoIsotopic Mass: 350.154976 ; (6)Topological Polar Surface Area: 18.8 ; (7)Heavy Atom Count: 25 ; (8)Complexity: 544 ; (9)Defined Bond StereoCenter Count: 1 ; (10)Covalently-Bonded Unit Count: 2.

People can use the following data to convert to the molecule structure. SMILES: [Cl-].c1cccc2c1c(c(n2)C)\C=C\C4=[N+](\c3ccccc3C4(C)C)C; InChI:InChI=1/C22H22N2.ClH/c1-15-16(17-9-5-7-11-19(17)23-15)13-14-21-22(2,3)18-10-6-8-12-20(18)24(21)4;/h5-14H,1-4H3;1H.

The following is the toxicity data which has been tested.