Synthesis and crystal structure analysis of 4,4'-oxydianiline

The title compound, 4,4'-Oxydianiline, was synthesized in good yield by the reaction of 4-fluoro nitrobenzene with 4-nitrophenol in dimethylacetamide (DMAc) and toluene at 165 ˚C for 4 h in the presence of K2CO3 to obtain 4,4'- dinitrodiphenyl ether, which was then treated with Pd/C in N, N-dimetyl formamide (DMF) at 65 ˚C for 12 h. The crude product was recrystallized and elucidated by spectroscopic techniques (H NMR, LC-MS), elemental analyses. The compound crystallizes in the orthorhombic crystal system with space group P2₁2₁2₁ with unit cell parameters: a = 5.7203(10) Å, b = 7.7326(14) Å, c = 22.8219(42) Å and Z = 4. The crystal structure has been solved by using direct methods and refined by full-matrix least squares procédures to a final R-factor of 0.028 for 1835 observed reflections. The structure exhibits intermolecular H-bonds of the type N–H⋅⋅⋅O and N–H⋅⋅⋅N. N–H⋅⋅⋅π interactions are also observed in the structure.

Synthetic Procedure for 4,4′-Diaminodiphenyl Ether (4)

A mixture of(3,10.50 g,31.2 mmol)and (0.3 g,10%)of Pd/C in 150 mL of N,N-dimetyl formamide (DMF)was stirred at 65C for 12 h under hydrogen atmosphere.The Pd/C was then removed by filtration;the solvent was evaporated under reduced pressure of 15-20 torr and the title compound(4)was then obtained by distillation under reduced pressure as shown in Fig.-1.

Crystal Structure

The molecular structure containing atomic labeling is shown in Fig.-4 (ORTEP). The molecular structure consists of two benzene rings which are essentially planar, with atom C5 and C7 displaced out of their mean ring planes by -0.0071Å and -0.0025Å, respectively. Bond distances, bond angles and torsion angles which play an important role in collating the structural properties of the molecule are presented in Table-2.

All the bond distances are in normal range (except C3-N1 and C10-N2) and are comparable with the values observed for some analogous structures. The C3-N1 [1.387(19) Å] and C10-N2 [1.402(17) Å] bond distance is smaller than the standard value of 1.470 Å. The benzene ring A makes a dihedral angle of 79.44° with ring B.

In the crystal structure, there exist two intermolecular hydrogen bonds N2-H2A…O1 and N2-H2B…N2, respectively [Fig.-5] (Mercury). Molecular packing in the unit cell as viewed down the a-axis is shown in Figure-6 (PLATON). The details of intra/inter-molecular hydrogen bonds are given in Table-3. The N-H…π contacts as observed in the molecular packing are given in Table-4.

References:

[1] GOPAL SHARMA. SYNTHESIS AND CRYSTALLOGRAPHIC STRUCTURE ANALYSIS OF 4,4’-OXYDIANILINE[J]. Rasayan Journal of Chemistry, 2019. DOI:10.31788/rjc.2019.1245305.