The Mefenpyr with its cas register number is 135591-00-3. It also can be called as 1-(2,4-Dichlorophenyl)-4,5-dihydro-5-methyl-1H-pyrazole-3,5-dicarboxylic acid and the IUPAC Name about this chemical is 1-(2,4-dichlorophenyl)-5-methyl-4H-pyrazole-3,5-dicarboxylic acid. 

Physical properties about Mefenpyr are: (1)ACD/LogP: 1.10; (2)ACD/LogD (pH 5.5): -3.55; (3)ACD/LogD (pH 7.4): -3.65; (4)ACD/BCF (pH 5.5): 1; (5)ACD/BCF (pH 7.4): 1; (6)ACD/KOC (pH 5.5): 1; (7)ACD/KOC (pH 7.4): 1; (8)#H bond acceptors: 6; (9)#H bond donors: 2; (10)#Freely Rotating Bonds: 3; (11)Polar Surface Area: 68.2Ų; (12)Index of Refraction: 1.661; (13)Molar Refractivity: 72.71 cm³; (14)Molar Volume: 196.5 cm³; (15)Polarizability: 28.82x10^-24cm³; (16)Surface Tension: 61.1 dyne/cm; (17)Enthalpy of Vaporization: 85.18 kJ/mol; (18)Vapour Pressure: 3.34E-12 mmHg at 25°C.

You can still convert the following datas into molecular structure:
(1)Canonical SMILES: CC1(CC(=NN1C2=C(C=C(C=C2)Cl)Cl)C(=O)O)C(=O)O
(2)InChI: InChI=1S/C12H10Cl2N2O4/c1-12(11(19)20)5-8(10(17)18)15-16(12)9-3-2-6(13)4-7(9)14/h2-4H,5H2,1H3,(H,17,18)(H,19,20)
(3)InChIKey: XEJNEDVTJPXRSM-UHFFFAOYSA-N