Pyridazine
1,2- diazine
Colorless to yellow- brown liquid
Liquid
1.10535 g · cm -3 at 20.0 ° C
-8 ° C
208 ° C
- Completely miscible with water, dioxane and ethanol
- Soluble in benzene and diethyl ether
- Almost insoluble in cyclohexane and ligroin
1.52311 at 23.5 ° C
224.9 kJ / mol
Template: Infobox chemical / molecular formula search available
Pyridazine is a heterocyclic aromatic organic compound. It consists of a six-membered ring having two adjacent nitrogen atoms. The systematic name is 1,2- diazine, the compound has the molecular formula C4H4N2. Pyridazine belongs to the group of Diazines and forms the main body of the pyridazines which are isomeric with the pyrimidines and pyrazines.
Properties
Pyridazine colorless to yellow- brown liquid which is miscible with water. Your hydrochloride is a yellow solid which melts at 161-163 ° C. Your Monopikrat and chloroaurate are also yellow solids which decompose at 170 ° C or 110 ° C.
Pyridazine hückelaromatische is a compound having six π electrons. Both nitrogen atoms have nor ever a lone pair of electrons beyond. This allows the binding of the proton, and the complex formation with metals and metal ions.
Nitrogen atoms more electronegative than carbon atoms, and therefore is the electron density in aromatic compounds, in contrast to reduced benzene and also unevenly distributed. The highest electron density is located on the nitrogen atoms. Compared to pyridine diazines have another electron-withdrawing nitrogen atom, whereby the electron density in aromatic compounds is even lower in pyridine. Due to the competition of the two nitrogen atoms to the available electrons has pyridazine a lower basicity than pyridine on ( pK a values of the conjugate acids: pyridine: 5.23, pyridazine: 2.24 ).
Representation
After synthesis, originally described in 1901 by R. Marquis and 1942 by Hückel and Jahnentz revised furan is nitrated with a mixture of nitric acid and acetic anhydride; Nitroacetofuran the intermediate obtained is immediately further reacted with hydrazine hydrate with a moderate yield of 20 %.
Better yields are obtained in the reaction of maleic acid derivatives. Thus, maleic anhydride can successfully undergo hydrazinolysis. Then the resulting 1,2- dihydropyridazines -3 ,6- dione may be reacted with phosphorus oxychloride using H2 - Pd / C and up to 62 % yield by the chlorination pyridazine.
The reaction of hydrazine with Maleindialdehyd also leads to pyridazine. Due to the unstable character of the dialdehyde this is usually released in situ from its corresponding diacetals. The yield of this method could be increased to over 80 % in a BASF process by minor modifications of the original procedure ( in particular a change in the sequence of steps ):