scholarly journals Utilizing the Combined Power of Theory and Experiment to Understand Molecular Structure – Solid-State and Gas-Phase Investigation of Morpholine Borane

2020 ◽  
Vol 73 (8) ◽  
pp. 794
Author(s):  
Aliyu M. Ja'o ◽  
Derek A. Wann ◽  
Conor D. Rankine ◽  
Matthew I. J. Polson ◽  
Sarah L. Masters
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Gas Phase ◽  
Hydrogen Generation ◽  
Energy Requirement ◽  
Hydrogen Release ◽  
X Ray Diffraction ◽  
Structural Variations ◽  
Dehydrogenation Reaction ◽  
Quantum Chemical Methods

The molecular structure of morpholine borane complex has been studied in the solid state and gas phase using single-crystal X-ray diffraction, gas electron diffraction, and computational methods. Despite both the solid-state and gas-phase structures adopting the same conformation, a definite decrease in the B–N bond length of the solid-state structure was observed. Other structural variations in the different phases are presented and discussed. To explore the hydrogen storage potential of morpholine borane, the potential energy surface for the uncatalyzed and BH3-catalyzed pathways, as well as the thermochemistry for the hydrogen release reaction, were investigated using accurate quantum chemical methods. It was observed that both the catalyzed and uncatalyzed dehydrogenation pathways are favourable, with a barrier lower than the B–N bond dissociation energy, thus indicating a strong propensity for the complex to release a hydrogen molecule rather than dissociate along the B–N bond axis. A minimal energy requirement for the dehydrogenation reaction has been shown. The reaction is close to thermoneutral as demonstrated by the calculated dehydrogenation reaction energies, thus implying that this complex could demonstrate potential for future on-board hydrogen generation.

Trifluoromethylated Compounds with SiNN and SiON Backbone, and the Crystal Structures of Trimethyl- and Trichloro(trifluoromethyl)silane

2009 ◽  
Vol 64 (1) ◽  
pp. 83-92 ◽  
Author(s):  
Markus Woski ◽  
Norbert W. Mitzel
Keyword(s):  
Gas Phase ◽  
Solution Nmr ◽  
X Ray Diffraction ◽  
Experimental Ir ◽  
In Situ Techniques ◽  
Quantum Chemical Methods ◽  
Conformational Preferences ◽  
Donor Acceptor ◽  
Solid State Structures

The reaction of (F3C)Cl2SiCl3 with the lithiated hydrazine LiN(Me)NMe2 gives the compound (F3C)Cl2SiN(Me)NMe2 (1) and in traces Cl3SiN(Me)NMe2 (2). The reactions with LiN(SiMe3)NMe2 and LiONMe2 give (F3C)Cl2SiN(SiMe3)NMe2 (4) and (F3C)Cl2SiONMe2 (5), respectively. The compounds were characterised by multinuclear solution NMR, gas-phase IR spectroscopy and mass spectrometry. Information about conformational preferences of 1 and 4 can be extracted by comparing experimental IR spectra with those calculated by quantum chemical methods (B3LYP/6-311G**). The former show the gas phase of the β -donor-acceptor silanes 1 and 4 to be dominated by the anti conformations, while the calculations show a preference for the gauche conformers. The crystal structure of Cl3SiN(Me)NMe2 (2) has been determined. The solid-state structures of the Ruppert reagent F3C-SiMe3 (1) and its chlorine analogue F3C-SiCl3 (2) have also been determined by X-ray diffraction of single crystals grown by in situ techniques.

A structural and carbon-nitrogen bond rotation study of N,N,N',N',2,2-hexamethylpropanediamide

1983 ◽  
Vol 36 (9) ◽  
pp. 1865 ◽  
Author(s):  
SF Lincoln ◽  
AM Hounslow ◽  
NJ Maeji ◽  
TW Hambley ◽  
MR Snow ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Kinetic Parameters ◽  
Methyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Rotation ◽  
Nitrogen Bonds ◽  
Rotation Study ◽  
Nitrogen Bond

The molecular structure of N,N,N',N',2,2-hexamethylpropanediamide has been determined in the solid state by X-ray diffraction methods. The structure of Me2NCOCMe2CONMe2 may be broadly described as two planar Me2NCO entities intersecting at the tetrahedral -CMe2- site. The angle between the normals to the two Me2NCO planes is 104.6�, and the two oxygen atoms are disposed outwards from the molecule and away from each other. Proton (270-MHz) n.m.r. studies yield k(320 K) 32.0 � 3.2 s-1, ΔH‡ 69.5 � 0.4 kJ mol-1 and ΔS‡ 0.6 � 1.1 J K-1 mol-1 for rotation of the N-methyl groups about the carbon-nitrogen bonds in CD3NO2 solution. Similar magnitudes for the kinetic parameters characterizing this process are obtained in CDCl3, and CD3CN solutions.

Molecular structure in the solid state (X-Ray diffraction) and in solution (1H and 13C NMR) of nifurtimox and two pyrazol-1-Yl analogs

2010 ◽  
Vol 97 (11-12) ◽  
pp. 1055-1066 ◽  
Author(s):  
Ma de la Concepción Foces-Foces ◽  
Félix Hernández Cano ◽  
Rosa Ma Claramunt ◽  
Alain Fruchier ◽  
José Elguero
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
13C Nmr ◽  
X Ray Diffraction ◽  
1H And 13C Nmr ◽  
X Ray

Configurations and conformations of glycosyl sulfoxides

2010 ◽  
Vol 88 (11) ◽  
pp. 1154-1174 ◽  
Author(s):  
Hong Liang ◽  
Micheline MacKay ◽  
T. Bruce Grindley ◽  
Katherine N. Robertson ◽  
T. Stanley Cameron
Keyword(s):  
Solid State ◽  
Dft Calculations ◽  
Gas Phase ◽  
Density Functional ◽  
Lone Pair ◽  
Azido Group ◽  
X Ray Diffraction ◽  
X Ray ◽  
Comparison Of The Results ◽  
P Type

X-ray crystallographic studies of two axial glycosyl sulfoxides having RS configurations (derivatives of phenyl 2-azido-2-deoxy-1-thio-α-d-galactopyranoside S-oxide) show that they adopt anti conformations in the solid state, in contrast to previous observations and assumptions. Density functional theory (DFT) calculations at the B3lYP6–311G+(d,p)/6–31G(d) level confirm that anti conformations of both phenyl and methyl RS glycosyl sulfoxides of 2-azido-2-deoxy-α-d-pyranosides are more stable than exo-anomeric conformations in the gas phase. 1D NOE measurements indicate that the more polar exo-anomeric conformers are only populated to a slight extent in solution. The anti conformations are distorted so that the glycosyl substituents are closer to being eclipsed with H1. This distortion allows S n → σ* overlap if the sulfur lone pair is a p-type lone pair. Evidence for this overlap comes from short C1–S bond distances, as short as the comparable bond distances in the X-ray crystal structure and in the results from DFT calculations for the SS glycoside, which does adopt the expected exo-anomeric conformation, both in the solid state and in solution, and has normal n → σ* overlap. For 2-deoxy derivatives not bearing a 2-azido group, gas-phase DFT calculations at the same level indicate that the anti- and exo-anomeric conformers have comparable stabilities. Comparison of the results of the two series shows that electronegative substituents in equatorial orientations at C2 destabilize conformations with parallel S–O arrangements, the conformation favored by having an endocyclic C–O dipole antiparallel to the S–O dipole, by about 2.5 kcal mol–1 (1 cal = 4.184 J). An equatorial glycosyl sulfoxide, (SS) phenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-1-thio-β-d-glucopyranoside S-oxide, also adopts an anti conformation in the solid state as shown by X-ray diffraction. It also adopts this conformation in solution, in contrast to studies of other equatorial glycosyl sulfoxides.

CuAl2 Intermetallic Hydrogen Evaluation after Mechanical Activation of Powders

2014 ◽  
Vol 793 ◽  
pp. 127-134 ◽  
Author(s):  
J. Luis López-Miranda ◽  
Tiberio A. Reyes-Hernández ◽  
Ares G. Hernández-Torres ◽  
J.R. Romero-Romero ◽  
R. Pérez ◽  
...  
Keyword(s):  
Mechanical Activation ◽  
Chemical Reaction ◽  
Room Temperature ◽  
Hydrogen Generation ◽  
Hydrogen Release ◽  
X Ray Diffraction ◽  
X Ray ◽  
Aluminum Hydroxides ◽  
Mechanical Attrition ◽  
Diffraction Patterns

Water vapor in the air affects aluminum based intermetallic compounds to form hydrogen. We take advantage of this fact to explore the amount of hydrogen obtained from CuAl2 intermetallic after its mechanical attrition activation. For this propose, CuAl2 intermetallic alloy was first produced by conventional casting methods and then subjected to mechanical milling processing. After the mechanical activation of the CuAl2 powders, a chemical reaction between them and water was carried out at room temperature including additives such as CaO, Al and NaCl. The amount of hydrogen release was correlated with other phases produced after the chemical reaction. X-ray diffraction patterns and scanning electron microscopy studies indicates that these phases were aluminum hydroxides and cupper oxides. According to these studies, a significant presence of oxide and hydroxide products occurred in the samples with NaCl additions, indicating best capability for hydrogen generation.

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