3,4-Dihydroxybenzaldehyde, its cas register number is 139-85-5. It also can be called Protocatechualdehyde; Rancinamycin IV; and 4-Formyl-1,2-dihydroxybenzene. It is hazardous, so the first aid measures and others should be known. In addition, 3,4-Dihydroxybenzaldehyde could be stable under normal temperatures and pressures. 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 monoxide, carbon dioxide.  3,4-Dihydroxybenzaldehyde is an important pharmaceutical intermediate, and can be used for synthesis of antibiotics and anti-inflammatory drugs.

Physical properties about 3,4-Dihydroxybenzaldehyde are: (1)ACD/LogP: 0.934; (2)ACD/LogD (pH 5.5): 0.93; (3)ACD/LogD (pH 7.4): 0.72; (4)ACD/BCF (pH 5.5): 2.99; (5)ACD/BCF (pH 7.4): 1.84; (6)ACD/KOC (pH 5.5): 76.12; (7)ACD/KOC (pH 7.4): 46.86; (8)#H bond acceptors: 3; (9)#H bond donors: 2; (10)Index of Refraction: 1.674 ; (11)Molar Refractivity: 36.769 cm³; (12)Molar Volume: 97.959 cm³; (13)Polarizability: 14.576 10-24cm³; (14)Surface Tension: 69.0270004272461 dyne/cm; (15)Density: 1.41 g/cm³; (16)Flash Point: 146.695 °C; (17)Enthalpy of Vaporization: 55.655 kJ/mol; (18)Boiling Point: 295.418 °C at 760 mmHg; (19)Vapour Pressure: 0.00100000004749745 mmHg at 25°C

When you are using this chemical, please be cautious about it as the following:
1. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice;
2. Wear suitable protective clothing;
3. Wear suitable gloves and eye/face protection;

You can still convert the following datas into molecular structure:
(1)InChI=1S/C7H6O3/c8-4-5-1-2-6(9)7(10)3-5/h1-4,9-10H;
(2)InChIKey=IBGBGRVKPALMCQ-UHFFFAOYSA-N;
(3)Smilesc1(cc(c(O)cc1)O)C=O

The toxicity data is as follows: