Abstract
The gem-aminals of 1,2-dimorpholinoethane (1) and 1-morpholino-3-morpholinium bromide propane (2) were synthesized by reaction of two molar ratio of morpholine with the halogenating agents in the presence of basic condition (K2CO3) in acetone at room temperature (RT) overnight. The structures of the centro-symmetric compound 1 and the morpholinium salt derivative 2 were assigned unambiguous by single crystal X-ray diffraction analysis and compared with the 1,2-di(pyrrolidin-1-yl)ethane 3 and 1,2-di(piperidin-1-yl)ethane 4. The 1,2-dimorpholinoethane molecule has a center of symmetry at the midpoint of the C-C bond of the ethyl moiety leading to two equivalent halves. It crystallized in monoclinic crystal system and P21/n space group, while the unit cell parameters are determined to be a = 6.0430(3), b = 8.0805(3), c = 11.1700(4) Å, and β = 97.475(2)° with unit cell volume of 540.80(4) Å3 and Z = 2 at 170(2) K. The less symmetric analogue 2 crystallized in the lower space group P21 with unit cell parameters of a = 6.37450(10), b = 11.1378(2), c = 9.6549(2) Å, and β = 93.358(2)°, while the unit cell volume is 684.30(2)Å3 at 120(2) K. Using Hirshfeld analysis, the molecules of 1 are mainly packed by weak N…H (4.2%), O…H (16.8%), and H…H (79.0%) interactions. In contrast, the molecules of 2 are packed by significantly short O…H (14.4%) and Br…H (11.6%) interactions in addition to the relatively long H…H (73.3%) interactions. DFT calculations predicted the molecular geometry of the studied compounds showing a good agreement with the experimental X-ray structures. Due to symmetry considerations, compounds 1, 3, and 4 are nonpolar with zero dipole moment, while the less symmetric molecule 2 has a dipole moment of 6.914 Debye. Their electronic aspects, such as natural population charges, HOMO, and LUMO energies as well as the corresponding reactivity descriptors, were also calculated and discussed.
Highlights
Aminals linked with a spacer were studied extensively in a wide area of chemistry aspects
Aminals were employed as building blocks for the synthesis of gemini basic ionic liquids
This type of ionic liquids was recently investigated as environmental benign catalysts in organic synthesis due to high chemical and thermal stability with low vapor pressure and low viscosities [1,2,3,4,5,6]
Summary
Aminals (gem-dimaines) linked with a spacer were studied extensively in a wide area of chemistry aspects. The diamines worked as N-donor ligands and chiral auxiliaries with many of metal ions such as Ca [7], Fe [8], Ag [9], Ni [10], Pd [11], and Rh [12], it explored in various catalyzed protocols and were successively employed as efficient catalysts for many transformations in organic synthesis. In this aspect, the aminals (gem-diamines) have been considered as promising electrophiles in metal-catalyzed nucleophilic addition reactions [13]. Given to the prevalence of diamines, there is a need for doing structure elucidation and studying their chemical insights [17]
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