Hydrogen atom release from methyl groups of energized molecules

1999 ◽  
Vol 110 (20) ◽  
pp. 9956-9960 ◽  
Author(s):  
Zhiyuan Min ◽  
Teh-Hwa Wong ◽  
Richard Bersohn
Keyword(s):  
Hydrogen Atom ◽  
Methyl Groups ◽  
Atom Release

Hydrogen Atom Release Dynamics in Radical–Radical Reactions: Saturated vs Unsaturated

ChemPhysChem ◽  
2008 ◽  
Vol 9 (8) ◽  
pp. 1099-1103 ◽  
Author(s):  
Sung-Eui Youn ◽  
You-Hwa Ok ◽  
Jong-Ho Choi
Keyword(s):  
Hydrogen Atom ◽  
Radical Reactions ◽  
Atom Release

Ab initio studies on amides: conformational preferences of diacetamide and barriers to interconversion of the conformers

1980 ◽  
Vol 33 (11) ◽  
pp. 2337 ◽  
Author(s):  
L Radom ◽  
NV Riggs
Keyword(s):  
Hydrogen Atom ◽  
Ab Initio ◽  
Internal Rotation ◽  
Model Systems ◽  
Methyl Groups ◽  
Electrostatic Repulsion ◽  
Conformational Preferences ◽  
Out Of Plane ◽  
Model Transition ◽  
Good Agreement

Diacetamide, like other diacylamines, is capable of existing in three basic conformations about the N-C bonds. Optimization (STO-3G) of model systems in which all first-row atoms and the amido hydrogen atom are held coplanar predicts that the E,Z conformer (3) is of lowest energy, the Z,Z conformer (2) of somewhat higher energy (4.2 kJ mol-1), and the E,E conformer (1) of highest energy (23.6 kJ mol-1); 4-31G evaluation of the energies suggests that (1) and (2) are each of higher energy than (3) by 27-28 kJ mol-1. It is suggested that (2) is destabilized with respect to (3) by electrostatic repulsion of the two negatively charged oxygen atoms whereas destabilization of (1) is due to substantial methyl-methyl steric interactions as reflected in the very wide <CNC (136°); the energy of (1) is, however, raised by out-of-plane or rotational movements of the methyl groups, i.e., the preferred structure (excluding methyl hydrogens) is planar. The calculated height of the barrier to internal rotation of (3) by either of two model transition states is 41-45 kJ mol-1, in good agreement with an experimental value of 45.2 kJ mol-1 in solution at -60°.

An anomalous effect of methyl group on acidity of acylthioureas

1987 ◽  
Vol 52 (8) ◽  
pp. 1992-1998 ◽  
Author(s):  
Jaromír Kaválek ◽  
Josef Jirman ◽  
Vladimír Macháček ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Acetyl Derivative ◽  
Methyl Groups ◽  
Anomalous Effect ◽  
Methyl Group ◽  
Methyl Derivatives

Dissociation constants and methanolysis rate constants have been measured of 1-acetyl- and 1-benzoylthioureas and their N-methyl derivatives. Replacement of hydrogen atom at N(1) (next to the acyl group) by methyl group increases the acidity of the benzoyl derivative by one order, that of the acetyl derivative by as much as two orders of magnitude. Replacement of both hydrogens at N(3) by methyl groups lowers the methanolysis rate constant by more than two orders, whereas the replacement of hydrogen atom at N(1) by methyl group increases the methanolysis rate by the factor of 30.

Synthesis, characterization, and investigation of the antioxidant activity of some 1,2,4-benzothiadiazine-1,1-dioxides bearing sulfonylthioureas moieties

2019 ◽  
Vol 97 (12) ◽  
pp. 824-832 ◽  
Author(s):  
Kamel Harrouche ◽  
Asma Lahouel ◽  
Mebrouk Belghobsi ◽  
Bernard Pirotte ◽  
Smail Khelili
Keyword(s):  
Lipid Peroxidation ◽  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Hydrogen Atom ◽  
Crucial Role ◽  
Reducing Power ◽  
Methyl Groups ◽  
Methyl Group ◽  
The Future ◽  
Reducing Power Assay

A series of 1,2,4-benzothiadiazine-1,1-dioxides bearing a sulfonylthiourea moiety were synthesized, characterized, and screened for their antioxidant activity, using six antioxidant analytical assays comparatively to reference compounds, ascorbic acid and quercetin. The results indicated that several compounds demonstrated strong antioxidant activity in DPPH, ABTS, H2O2, and lipid peroxidation assays where some of them were either as active as or more active than reference compounds. However, all compounds were largely less active than references compounds in the reducing power assay. The results indicated that the thiourea moiety probably played a crucial role in the antioxidant activity of the target compounds, as a thiolate ion. The most favorable R1 groups were the hydrogen atom and methyl group, followed by phenyl and benzyl groups, whereas the most favorable R2 group was iPr, followed by the phenyl and methyl groups. The combination of benzothiadiazine ring with sulfonylthiourea moieties led to valuable new antioxidants, which could be used in the treatment or the prevention of certain diseases or in the field of cosmetics, which needs further investigations in the future.

Crystal and molecular structure of (RS,RS)-Tetraammine(4,5-dihydroxy-4,5-dimethyl-1-pyrroline-2-carboxylato)cobalt(III) perchlorate

1975 ◽  
Vol 28 (10) ◽  
pp. 2129 ◽  
Author(s):  
GB Robertson ◽  
PO Whimp
Keyword(s):  
Molecular Structure ◽  
Hydrogen Atom ◽  
Crystal And Molecular Structure ◽  
Three Dimensional ◽  
Methyl Groups ◽  
Monoclinic Space Group ◽  
Hydrogen Atoms ◽  
Steric Strain ◽  
X Ray ◽  
R Factors

The structure of a cobalt(III) tetraammine complex of 4,5-dihydroxy- 4,5-dimethyl-1-pyrroline-2-carboxylic acid (abbreviated as hmpc), (RS,RS)-[Co(NH3)4(hmpc)] (ClO4)2,H2O, has been determined from three- dimensional X-ray data collected by counter methods. Crystals are monoclinic, space group P21/c, with a 11.984(5), b 8.836(4), c 19.609(7) Ǻ, β 110.58(2)�, Z 4. The structure has been refined to weighted and unweighted R-factors of 0.068 and 0.063, respectively, for the 1616 independent reflections with I/σ(I) ≥ 3.0. Hydrogen atoms could not be located and have not been included in the scattering model. There is considerable steric strain within the substituted pyrroline ligand, and the C=N distance is 1.293(8) Ǻ. Surprisingly, the methyl groups in the 4- and 5-positions are in a cisoid configuration (the torsion angle for the methyl groups about the 4-5 bond is 39.5�), and consequently the hydroxyl oxygen atoms are close [O-O distance, 2.583(8) Ǻ]; this suggests that there may be a bridging hydrogen atom.

Exploring the dynamics of hydrogen atom release from the radical–radical reaction of O(3P) with C3H5

2004 ◽  
Vol 120 (17) ◽  
pp. 7976-7982 ◽  
Author(s):  
Sun-Kyu Joo ◽  
Lee-Kyoung Kwon ◽  
Hohjai Lee ◽  
Jong-Ho Choi
Keyword(s):  
Hydrogen Atom ◽  
Radical Reaction ◽  
Atom Release

Impact of DNA Environment on the Intrastrand Cross-Link Lesions: Hydrogen Atom Release as the Last Step of Formation of G[8-5m]T

2013 ◽  
Vol 117 (51) ◽  
pp. 16397-16404 ◽  
Author(s):  
José Pedro Cerón-Carrasco ◽  
Denis Jacquemin ◽  
Elise Dumont
Keyword(s):  
Hydrogen Atom ◽  
Cross Link ◽  
Atom Release

scholarly journals 2,3-Dimethyl-1H-imidazol-3-ium benzenesulfonate–1,2-dimethyl-1H-imidazole co-crystal

IUCrData ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Noah Cyr ◽  
Matthias Zeller ◽  
Patrick C. Hillesheim ◽  
Arsalan Mirjafari
Keyword(s):  
Hydrogen Atom ◽  
Imidazole Ring ◽  
Strong Hydrogen Bond ◽  
Methyl Groups ◽  
Benzene Sulfonate ◽  
Asymmetric Unit ◽  
Charge Balance ◽  
Imidazolium Cations ◽  
Sulfonate Anion ◽  
Acidic Hydrogen

In the title co-crystal, C5H9N2 +·C6H5O3S−·C5H8N2, the two 1,2-dimethylimidazole rings exist as partially protonated moieties in the asymmetric unit as a two-part disordered unit wherein the acidic hydrogen atom is bound to each ring. The two imidazolium cations share a strong hydrogen bond via the acidic hydrogen atom, which is disordered between two positions, being bonded to the first versus second imidazole ring in a 0.33 (2) to 0.67 (2) ratio. A benzene sulfonate anion is present for charge balance and interacts with the aromatic H atoms on both imidazole rings as well as with the methyl groups on the rings.

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