Crystal structure of 2,4,5-tribromo-1-methyl-1H-imidazole, C₄H₃Br₃N₂

Abstract

C 4H3Br3N2,t riclinic, P1 (no. 2), a =6.9066(3) Å, b =7.0812(3) Å, c =16.1046(6) Å, α =78.093(2)°, β =82.467(2)°, γ =89.781(2)°,Source of material 1-Methyl-1H-imidazole (24.6 g, 0.3 mol) and sodium acetate trihydrate (100 g, 0.7 mol) were dissolved in 350 ml glacial acetic acid and asolution of bromine (143.6 g, 0.9 mol) in 50 ml of glacial acetic acid was added slowly under cooling. The resulting solution was stirred overnight and then poured onto 500 ml of ice water. The precipitate of 2,4,5-tribromo-1-methyl-1H-imidazole was filtered off and recrystallized from aqueous ethanol. Yield: 50.0 g(52 %), mp. 93°C. DiscussionAlready in the late 19th century Wyss and Wallach reported the correct molecular formula of 2,4,5-tribromo-1-methyl-1H-imidazole and they discussed possible chemical structures [1,2].Until now there has been no X-ray determination of the crystal structure of this compound. The imidazole core is akey for ahuge variety of important biologically active substances. It has found many applications in metalcarbene catalysts and is most important in ionic liquids (ILs) and magnetic ILs [3][4][5][6][7][8]. Polybrominated imidazole building blocks are useful as starting materials in the synthesis of very dense halogenated ILs [9]. The title compound crystallizes with two symmetry independent molecules in the asymmetric unit. The orientation of the molecules gives short hydrogen-bonding contacts between Br atoms and methyl groups of neighbouring units. The figure shows such an intermolecular hydrogen-bonding contact as thermal ellipsoid plot at the 50 %probability level.

Fast and accurate prediction of the regioselectivity of electrophilic aromatic substitution reactions

“… 16 – 18 In fact all three positions in N -methylimidazole can be halogenated which is not surprising given the fact the calculations suggest that the three possible arenium ions have similar standard free energies. 19 – 21 Finally, a 1 : 1 mixture of the 4- and 5-brominated products has been reported for N -benzylimidazole, which is in line with the predictions. 22 , 23…”

Fast and Accurate Prediction of the Regioselectivity of Electrophilic Aromatic Substitution Reactions

“…[16][17][18] In fact all three positions in N-methylimidazole can be halogenated which is not surprising given the fact the calculations suggest that the three possible arenium ions have similar standard free energies. [19][20][21] Finally, a 1 : 1 mixture of the 4-and 5-brominated products has been reported for N-benzylimidazole, which is in line with the predictions. 22,23 Computational methodology…”

Halogen bonds with carbenes acting as Lewis base units: complexes of imidazol-2-ylidene: theoretical analysis and experimental evidence

“…3c shows an example, the fragment of the 2,4,5-tribromo-1-methyl-1H-imidazole crystal structure where the C-BrÁ Á ÁBr halogen bonds are observed. 73…”