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1,2-Dinitrobenzene is one of three isomers of dinitrobenzene, with the formula C 6 H 4 (NO 2) 2. The compound is a white or colorless solid that is soluble in organic solvents. It is prepared from 2-nitroaniline by diazotization and treatment with sodium nitrite in the presence of a copper catalyst. [1]
The three possible arrangements of the nitro groups afford three isomers, 1,2-dinitrobenzene, 1,3-dinitrobenzene, and 1,4-dinitrobenzene. Each isomer has the chemical formula C 6 H 4 N 2 O 4 and a molar mass of about 168.11 g/mol. 1,3-Dinitrobenzene is the most common isomer and it is used in the manufacture of explosives.
In contrast, 2-methyl-1,4-dinitrobenzene (2c) is isolated in only 9.9% yield. [4] As witnessed in the above example, when a π-acceptor substituent (πAS) is meta to a π-donor substituent (πDS), the electrophilic aromatic nitration occurs ortho to the πAS rather than para.
A comparison of S N 1 to S N 2 reactions is to the right. On the left is an S N 1 reaction coordinate diagram. Note the decrease in ΔG ‡ activation for the polar-solvent reaction conditions. This arises from the fact that polar solvents stabilize the formation of the carbocation intermediate to a greater extent than the non-polar-solvent ...
The gauche effect is very sensitive to solvent effects, due to the large difference in polarity between the two conformers.For example, 2,3-dinitro-2,3-dimethylbutane, which in the solid state exists only in the gauche conformation, prefers the gauche conformer in benzene solution by a ratio of 79:21, but in carbon tetrachloride, it prefers the anti conformer by a ratio of 58:42. [9]
Likewise, larger molecules are generally more polarizable than smaller ones. Water is a very polar molecule, but alkanes and other hydrophobic molecules are more polarizable. Water with its permanent dipole is less likely to change shape due to an external electric field. Alkanes are the most polarizable molecules. [9]
Space-filling model of a 1,2-dinitrobenzene molecule, C 6 H 4 N 2 O 4, also known as ortho-dinitrobenzene or o-dinitrobenzene. The molecule is shown as found in the crystal structure reported in Acta Crystallogr. B (1990) 46, 567–572 and CSD entry ZZZFYW01. Colour code: Carbon, C: grey Hydrogen, H: white Nitrogen, N: blue
Ball-and-stick model of a 1,2-dinitrobenzene molecule, C 6 H 4 N 2 O 4, also known as ortho-dinitrobenzene or o-dinitrobenzene. The molecule is shown as found in the crystal structure reported in Acta Crystallogr. B (1990) 46, 567–572 and CSD entry ZZZFYW01. Colour code: Carbon, C: grey Hydrogen, H: white Nitrogen, N: blue