The Propyl Red, with the CAS registry number 2641-01-2 and EINECS registry number 220-140-8, has the systematic name of 2-{(E)-[4-(dipropylamino)phenyl]diazenyl}benzoic acid. It is a kind of dark grey to very dark green crystalline powder, and usually be used as acid-base indicator. And the molecular formula of the chemical is C₁₉H₂₃N₃O₂.

The characteristics of Propyl Red are as followings: (1)ACD/LogP: 7.04; (2)# of Rule of 5 Violations: 1; (3)ACD/LogD (pH 5.5): 5.31; (4)ACD/LogD (pH 7.4): 4.01; (5)ACD/BCF (pH 5.5): 2482.34; (6)ACD/BCF (pH 7.4): 124.75; (7)ACD/KOC (pH 5.5): 3033.2; (8)ACD/KOC (pH 7.4): 152.43; (9)#H bond acceptors: 5; (10)#H bond donors: 1; (11)#Freely Rotating Bonds: 8; (12)Polar Surface Area: 54.26 Å²; (13)Index of Refraction: 1.568; (14)Molar Refractivity: 96.41 cm³; (15)Molar Volume: 294.4 cm³; (16)Polarizability: 38.22×10^-24cm³; (17)Surface Tension: 41.7 dyne/cm; (18)Density: 1.1 g/cm³; (19)Flash Point: 265.7 °C; (20)Enthalpy of Vaporization: 82.94 kJ/mol; (21)Boiling Point: 515.8 °C at 760 mmHg; (22)Vapour Pressure: 1.83E-11 mmHg at 25°C.

You should be cautious while dealing with this chemical. It is harmful by inhalation, in contact with skin and if swallowed. It may also cause carcinogenic effect, and it has risk of serious damage to eyes. Therefore, you had better take the following instructions: Do not breathe dust, and wear suitable protective clothing, gloves.

Addtionally, the following datas could be converted into the molecular structure:
(1)SMILES: O=C(O)c2ccccc2/N=N/c1ccc(N(CCC)CCC)cc1
(2)InChI: InChI=1/C19H23N3O2/c1-3-13-22(14-4-2)16-11-9-15(10-12-16)20-21-18-8-6-5-7-17(18)19(23)24/h5-12H,3-4,13-14H2,1-2H3,(H,23,24)/b21-20+
(3)InChIKey: LIIDWKDFORMMDQ-QZQOTICOBG