# A Comprehensive Study of N-Butyl-1H-Benzimidazole

^{1}

^{2}

^{3}

^{4}

^{5}

^{6}

^{7}

^{8}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Result and Discussion

#### 2.1. Structural Analysis of N-Butyl-1H-Benzimidazole

#### 2.2. Topological Analysis

^{2}ρ(r), the potential energy density V(r), the interaction energy Einteractions, and the ratio │V│/G. However, the values |V(r)|/G(r) make it possible to judge the nature of interactions: for covalent bonds, this ratio is greater than 2; for mixed interactions it is between 1 and 2; and for ionic bonds, van der Waals interactions have a value less than 1 [29].

^{2}ρ(r) > 0 for all types (except RCP2) indicate closed-shell interactions typical of ionic bonds and van der Waals interactions.

^{2}ρ(r) is observed for NRCP1 (0.3993 a.u.), and the smallest for RCP2 (−0.0176 a.u.). It should be noted that the maximum values of ρ(r) and G(r) are observed for RCP2 and are 0.3888 and 0.3888 a.u., respectively, and also for this type of interaction, the minimum values of V(r) (−0.6782 a.u.), H(r) (−0.5589 a.u.), and Einteractions (−890.05 kJ/mol) are observed.

^{2}ρ(r) (0.0063–0.0069 a.u), ρ(r) (0.0017-0.0019 a.u), G(r) (−0.0008–0.0009 a.u), H(r) (0.0004 a.u), and E

_{interactions}−1.05 kJ/mol. It should be noted that the interaction between hydrogen and nitrogen in C-H…N and N-H…N differ significantly in all of the main parameters.

_{2}, F, CH

_{3}, etc.), the aromatic domain opens first near the substituted carbon and then near the metacarbon [31]. The orienting effects of electrophilic substitutions correlate with these bifurcations.

#### 2.3. MEP Analysis

#### 2.4. Frontier Molecular Orbital (FMO) Analysis

#### 2.5. Fukui Functions

^{+}(r), f

^{−}(r), f

^{0}(r)) defined by Kolandaivel et al. [62] are calculated using the following equations:

^{+}(r) = q

_{(N+1)}(r) − q

_{(N)}(r) for nucleophilic attack

^{−}(r) = q

_{(N)}(r) − q

_{(N−1)}(r) for electrophilic attack

^{0}(r) = 1/2 [q

_{(N+1)}(r) − q

_{(N−1)}(r)] for radical attack

^{+}(r) − f

^{−}(r)

#### 2.6. UV-Vis Analysis and NBO Analysis

^{(2)}) using the following equation:

_{j}, and ε

_{i}, q

_{i}are the diagonal NBO Fock matrix element, the diagonal elements, and the donor orbital occupancy, respectively.

^{(2)}, obtained from NBO calculations, are presented in Table S2. The larger the value of E

^{(2)}, the greater the degree of conjugation of the entire system [72,73]. The stabilization of the structure of N-Butyl-1H-benzimidazole is evidenced by the strong intramolecular interaction of σ- and π-electrons of donor C–N, C–C bonds with acceptor C–N, C–C bonds.

_{A}(%) and ED

_{B}(%) with percentage electron densities of about 62.45%, 58.02%, 63.96%, and 58.70% respectively. The σ(C22-H24) orbital with high occupancy 1.98933 a.u. has 60.09% (C22) character in an sp 3.25 hybrid and 39.91% (H24) character in an sp 0.04 hybrid. According to Table S3, it is clear that the natural hybrid orbital LP (1) (N27) having high occupancy (1.92917 a.u.) and low energy (−0.37999 a.u.) has a p-character (0.052%), whereas LP (1) (N26) occupies a high energy orbital (−0.26555 a.u) with p-character (69.99%) and low occupation number (1.57449 a.u).

#### 2.7. FTIR Analysis

**C-H group vibration**

^{−1}at 3110, 3089, 3080, 3070, 3059, 2987, 2983, 2979, 2953, 2936, 2926, 2923, 2919, and 2904 cm

^{−1}. The CH

_{2}scissor mode is assumed to be in the range 1463–1440 cm

^{−1}. Moreover, vibrations of the C-H group are observed at 1362, 1287, 1251, 1136, 1114, 1092, 993, 943, 882, and 820 cm

^{−1}. The results obtained agree with the works [76,77].

**C-C group vibration**

^{−1}are usually attributed to simple C–C bonding modes for benzene derivatives. In our case, in the calculated C-C spectra, stretching vibrations are observed at 1597, 1563, 1092, 1023, 882, and 759 cm

^{−1}. Bending vibrations of the C-C group are observed at 1430, 1362, 1272, 1231, 1184, 1054, and 866 cm

^{−1}. Torsion vibrations of the C-C group in the calculated spectra are observed at 1335, 1251, 1092, 943, 914, 908, 832, 820, and 723 cm

^{−1}.

**C-N group vibration**

^{−1}indicate a C=N double bond, while bands closer to 1300 cm

^{−1}indicate the presence of C-N bonds [78]. It is known [19] that vibrations of the C=N group of the imidazole group in benzimidazole are observed at 1490 cm

^{−1}. In our case, in the calculated spectra, C-N stretching vibrations are observed at 1477, 1362, 1344, 1264, and 1084 cm

^{−1}. Bending vibrations of the C-N group are observed at 1430, 1054, 832, and 759 cm

^{−1}. Torsion vibrations of the C-N group in the calculated spectra are observed at 1354, 1335, 832, and 617 cm

^{−1}.

#### 2.8. Mulliken Atomic Charges Analysis

## 3. Materials and Methods

_{c}and the Laplace electron density (∇

^{2}ρ

_{c}) at the bond critical points (BCPs). All wavefunction analysis was performed by Multiwfn 3.8 program [34]. Multiwfn program was used for topological analysis and to draw electron localization function diagram (ELF) using atom in molecule theory.

## 4. Conclusions

## Supplementary Materials

^{−1}) of N-Butyl-1H-benzimidazole calculated by means of VEDA 4 program; Table S5: Mulliken atomic charges of N-Butyl-1H-benzimidazole.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Sample Availability

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**Figure 9.**FTIR spectra of the title compound (blue line: experimental, red line: theoretical spectrum).

**Table 1.**The theoretical and experimental optimized structural parameters of N-Butyl-1H-benzimidazole.

B3LYP/6-311++G(d,p) | |||||
---|---|---|---|---|---|

Bond Lengths (A°) | Bond Angles (°) | ||||

Atom Position | Theo. | Exp. | Atom Position | Theo. | Exp. |

C_{1}-C_{2} | 1.415 | 1.398(2) | C_{2}-C_{1}-C_{6} | 122.3 | 107.0 |

C_{1}-C_{6} | 1.396 | 1.390(3) | C_{2}-C_{1}-N_{26} | 105.1 | 107.6 |

C_{1}-N_{26} | 1.386 | 1.391(2) | C_{6}-C_{1}-N_{26} | 132.6 | 107.5 |

C_{2}-C_{3} | 1.399 | 1.371(3) | C_{1}-C_{2}-C_{3} | 119.9 | 107.6 |

C_{2}-N_{27} | 1.387 | 1.367(2) | C_{1}-C_{3}-N_{27} | 110.1 | 107.6 |

C_{3}-C_{4} | 1.389 | 1.393(3) | C_{3}-C_{2}-N_{27} | 130.0 | 118.9(2) |

C_{3}-H_{8} | 1.084 | 0.930 | C_{2}-C_{3}-C_{4} | 118.1 | 107.7(2) |

C_{4}-C_{5} | 1.408 | 1.368(3) | C_{2}-C_{3}-H_{8} | 120.2 | 124(1) |

C_{4}-H_{9} | 1.084 | 0.930 | C_{4}-C_{3}-H_{8} | 121.7 | 128(1) |

C_{5}-C_{6} | 1.391 | 1.371(3) | C_{3}-C_{4}-C_{5} | 121.4 | 119.8(2) |

C_{5}-H_{10} | 1.084 | 0.930 | C_{3}-C_{4}-H_{9} | 119.6 | 109.4(2) |

C_{6}-H_{11} | 1.084 | 0.930 | H_{9}-C_{4}-C_{9} | 119.0 | 130.8(2) |

C_{7}-H_{12} | 1.082 | 0.80(2) | C_{4}-C_{5}-C_{6} | 121.5 | 105.5(2) |

C_{7}-N_{26} | 1.377 | 1.365(3) | C_{4}-C_{5}-H_{10} | 119.2 | 132.3(2) |

C_{7}-N_{27} | 1.306 | 1.317(2) | C_{6}-C_{5}-H_{10} | 119.2 | 122.2(2) |

C_{13}-H_{14} | 1.094 | 0.970 | C_{1}-C_{6}-C_{5} | 116.9 | 121.0 |

C_{13}-H_{15} | 1.095 | 0.970 | C_{1}-C_{6}-H_{11} | 122.2 | 118.0(2) |

C_{13}-C_{16} | 1.534 | 1.449(4) | C_{5}-C_{6}-H_{12} | 120.9 | 121.0 |

C_{13}-N_{26} | 1.458 | - | H_{12}-C_{7}-N_{26} | 120.7 | 121.5 |

C_{16}-H_{17} | 1.096 | 0.969 | H_{12}-C_{7}-N_{27} | 125.0 | 116.9(2) |

C_{16}-H_{18} | 1.095 | 0.970 | N_{26}-C_{7}-N_{27} | 114.3 | 121.6 |

C_{16}-C_{19} | 1.533 | 1.510(4) | H_{14}-C_{13}-H_{15} | 106.7 | 119.2 |

C_{19}-H_{20} | 1.097 | 0.970 | H_{14}-C_{13}-C_{16} | 110.2 | 121.6(2) |

C_{19}-H_{21} | 1.097 | 0.971 | C_{14}-C_{13}-N_{26} | 107.4 | 119.2 |

C_{19}-C_{22} | 1.531 | 1.417(5) | H_{15}-C_{13}-C_{16} | 110.5 | 121.5(2) |

C_{22}-H_{23} | 1.094 | 0.960 | H_{15}-C_{13}-N_{26} | 108.2 | 119.2 |

C_{22}-H_{24} | 1.093 | 0.960 | C_{16}-C_{13}-N_{26} | 113.6 | 119.3 |

C_{22}-H_{25} | 1.094 | 0.959 | C_{13}-C_{16}-H_{17} | 108.8 | 123.1(2) |

C_{13}-C_{16}-H_{18} | 109.3 | 124.8(2) | |||

C_{13}-C_{16}-C_{19} | 112.4 | 112.1(2) | |||

H_{17}-C_{16}-H_{18} | 106.4 | 108.3 | |||

H_{17}-C_{16}-C_{19} | 109.9 | 108.3 | |||

H_{18}-C_{16}-C_{19} | 109.8 | 115.7(2) | |||

C_{16}-C_{19}-H_{20} | 109.4 | 107.5 | |||

C_{16}-C_{19}-H_{21} | 109.4 | 108.4 | |||

C_{16}-C_{19}-C_{22} | 112.9 | 108.3 | |||

H_{20}-C_{19}-H_{21} | 106.1 | 107.8 | |||

H_{20}-C_{19}-C_{22} | 109.4 | 107.9 | |||

H_{21}-C_{19}-C_{22} | 109.4 | 117.8(3) | |||

C_{19}-C_{22}-H_{23} | 111.2 | 107.3 | |||

C_{19}-C_{22}-H_{24} | 111.3 | 107.9 | |||

C_{19}-C_{22}-H_{25} | 111.2 | 107.8 | |||

H_{23}-C_{22}-H_{24} | 107.7 | 109.5 | |||

H_{23}-C_{22}-H_{25} | 107.6 | 109.5 | |||

H_{24}-C_{22}-H_{25} | 107.7 | 109.5 | |||

C_{1}-N_{26}-C_{7} | 105.9 | 109.5 | |||

C_{1}-N_{26}-C_{13} | 127.4 | 109.4 | |||

C_{7}-N_{26}-C_{13} | 126.7 | 109.4 | |||

C_{2}-N_{27}-C_{7} | 104.6 | 105.4(2) |

**Table 2.**AIM topological parameters at BCPs (ρ: electron density; ∇

^{2}ρ: Laplacian of electron density; H: total energy density; V: potential energy density, and E

_{interactions}: interaction energy).

Interactions Types | ∇^{2}ρ(r) (a.u.) | ρ (r) (a.u.) | G(r) (a.u.) | V(r) (a.u.) | H(r) (a.u.) | ε | E_{interactions} kJ/mol |
---|---|---|---|---|---|---|---|

RCP1 | 0.0140 | 0.0040 | 0.0029 | −0.0023 | 0.0006 | −2.0003 | −3.02 |

RCP2 | −0.0176 | 0.3888 | 0.3888 | −0.6782 | −0.5589 | 0.0041 | −890.05 |

RCP3 | 0.0071 | 0.0018 | 0.0013 | −0.0009 | 0.0005 | −1.9466 | −1.18 |

RCP4 | 0.1673 | 0.0226 | 0.0342 | −0.0265 | 0.0077 | −1.2088 | −34.13 |

NRCP1 | 0.3993 | 0.0560 | 0.0939 | −0.0879 | 0.0059 | −1.2860 | −112.89 |

NRCP2 | 0.3980 | 0.0558 | 0.0936 | −0.0876 | 0.0059 | 1.2847 | −112.89 |

NRCP3 | 0.1671 | 0.0225 | 0.0341 | −0.0265 | 0.0077 | −1.2076 | −34.13 |

C_{43}-H_{45}…N_{26} | 0.0123 | 0.0033 | 0.0026 | −0.0022 | 0.0005 | 0.4900 | −28.88 |

N_{31}-H_{54}…N_{26} | 0.0874 | 0.0211 | 0.0182 | −0.0145 | 0.0037 | 0.0298 | −18.90 |

C_{7}-H_{8}…H_{16} | 0.0069 | 0.0019 | 0.0013 | −0.0009 | 0.0004 | 1.8492 | −1.05 |

C_{36}-H_{37}…H_{2} | 0.0063 | 0.0017 | 0.0012 | −0.0008 | 0.0004 | 2.9057 | −1.05 |

Quantum Parameters | DFT/B3LYP/6-31++G(d, p) |
---|---|

E_{HOMO}(eV) | −6.26 |

E_{LUMO}(eV) | −0.82 |

E_{HOMO+1}(eV) | −6.37 |

E_{LUMO-1} (eV) | −0.81 |

│ΔE_{HOMO-LUMO}│ (eV) | 5.44 |

│ΔE_{HOMO+1-LUMO-1}│ (eV) | 5.56 |

I | 6.26 |

A | 0.82 |

χ | 3.39 |

η | 2.72 |

µ | −3.39 |

ω | 2.11 |

S | 0.18 |

_{HOMO}− E

_{LUMO}│(eV), I = −E

_{HOMO}(eV), A = −E

_{LUMO}, χ = (I + A)/2, η = (I − A)/2, µ = −(I + A)/2, ω = µ

^{2}/2 η, S = 1/2 η.

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**MDPI and ACS Style**

Kazachenko, A.S.; Tanış, E.; Akman, F.; Medimagh, M.; Issaoui, N.; Al-Dossary, O.; Bousiakou, L.G.; Kazachenko, A.S.; Zimonin, D.; Skripnikov, A.M.
A Comprehensive Study of N-Butyl-1H-Benzimidazole. *Molecules* **2022**, *27*, 7864.
https://doi.org/10.3390/molecules27227864

**AMA Style**

Kazachenko AS, Tanış E, Akman F, Medimagh M, Issaoui N, Al-Dossary O, Bousiakou LG, Kazachenko AS, Zimonin D, Skripnikov AM.
A Comprehensive Study of N-Butyl-1H-Benzimidazole. *Molecules*. 2022; 27(22):7864.
https://doi.org/10.3390/molecules27227864

**Chicago/Turabian Style**

Kazachenko, Aleksandr S., Emine Tanış, Feride Akman, Mouna Medimagh, Noureddine Issaoui, Omar Al-Dossary, Leda G. Bousiakou, Anna S. Kazachenko, Dmitry Zimonin, and Andrey M. Skripnikov.
2022. "A Comprehensive Study of N-Butyl-1H-Benzimidazole" *Molecules* 27, no. 22: 7864.
https://doi.org/10.3390/molecules27227864