Log in

Relevant bibliographies by topics / Bond rotation / Journal articles

To see the other types of publications on this topic, follow the link: Bond rotation.

Journal articles on the topic 'Bond rotation'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Bond rotation.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Schaefer, Ted, Christian Beaulieu, and Rudy Sebastian. "2-Phenyladamantane as a model for axial phenylcyclohexane. 1H NMR and molecular orbital studies of motion about the Csp2—Csp3 bond." Canadian Journal of Chemistry 69, no. 3 (1991): 503–8. http://dx.doi.org/10.1139/v91-075.

Full text

Abstract:

The 1H NMR spectra of the aromatic groups of 2-phenylcyclohexane and 2-phenyladamantane, in CS2/C6D12 solution at 300 K, are analyzed to yield the long-range coupling constants between the α and ring protons. The coupling over six bonds is related to the internal rotational potential about the Csp2—Csp3 bond in these molecules. It is confirmed that the equatorial isomer of phenylcyclohexane has the parallel conformer, that in which the aromatic plane lies in the symmetry plane bisecting the cyclohexane moiety, as the most stable. The apparent twofold barrier to rotation about the exocyclic carbon–carbon bond follows as 7.1 kJ/mol from the six-bond coupling constant. For 2-phenyladamantane, the six-bond coupling constant strongly implies that the perpendicular conformer, perhaps slightly skewed, is that of lowest energy and that the apparent twofold barrier to rotation about the Csp2—Csp3 bond is about 7.5 kJ/mol. Insofar as 2-phenyladamantane mimics axial phenylcyclohexane, these results confirm recent conclusions about the conformation of the latter and provide evidence for its internal mobility. Geometry-optimized AMI and STO-3G MO computations are reported for the internal motion in both isomers of phenylcyclohexane. The former agree best with experiment for the equatorial isomer, but both imply a significant fourfold, of opposite sign to the twofold, component of the internal rotational potential. For the axial isomer, the two sets of computations find a skewed perpendicular conformer as most stable, in rough agreement with force-field results. However, the barrier to rotation about the Csp2—Csp3 bond is computed as small and AMI has the parallel conformer as more stable than the perpendicular. Key words: 2-phenyladamantane, 1H NMR and internal rotation; phenylcyclohexane, 1H NMR and internal rotation; MO computations, 2-phenyladamantane and phenylcyclohexane.

APA, Harvard, Vancouver, ISO, and other styles

2

Jalili, Seifollah, Farzad Molani, and Jeremy Schofield. "First principles study on energetic, structural, and electronic properties of defective g-C3N4-zz3 nanotubes." Journal of Theoretical and Computational Chemistry 13, no. 04 (2014): 1450021. http://dx.doi.org/10.1142/s0219633614500217.

Full text

Abstract:

The energetic, electronic and structural properties of defective g- C 3 N 4-zz3 nanotubes are considered based on spin-polarized density-functional theory calculations. Nine basic system types with vacancy defects are characterized by their stabilization energies and band gaps. It is found that the nitrogen atom denoted as N 3 is the most favorable atom for a vacancy defect. In all cases, local bond reconstruction occurs in the presence of vacancy defects. The role of C / N bond rotations on the above properties has been also investigated. The results show that N 1– C 3 bond rotation is the most favorable rotational defect. In addition, the electronic properties of the semiconducting g- C 3 N 4-zz3 nanotube with defects have been studied using band structure and density of states plots.

APA, Harvard, Vancouver, ISO, and other styles

3

Pérez-Torrente, Jesús J., Marta Angoy, Daniel Gómez-Bautista та ін. "Synthesis and dynamic behaviour of zwitterionic [M(η6-C6H5-BPh3)(coe)2] (M = Rh, Ir) cyclooctene complexes". Dalton Trans. 43, № 39 (2014): 14778–86. http://dx.doi.org/10.1039/c4dt02105c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Hong, Jung-Ho, Adil S. Aslam, Min-Sung Ko, Jonghoon Choi, Yunho Lee, and Dong-Gyu Cho. "Bond Rotation in an Aromatic Carbaporphyrin: Allyliporphyrin." Chemistry - A European Journal 24, no. 40 (2018): 10054–58. http://dx.doi.org/10.1002/chem.201802176.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Snyder, James P., Neysa Nevins, Sylvie L. Tardif, and David N. Harpp. "Inherently Hindered Rotation about a Disulfide Bond." Journal of the American Chemical Society 119, no. 51 (1997): 12685–86. http://dx.doi.org/10.1021/ja9728536.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Zhu, Qi-zhi, and Tao Ni. "Peridynamic formulations enriched with bond rotation effects." International Journal of Engineering Science 121 (December 2017): 118–29. http://dx.doi.org/10.1016/j.ijengsci.2017.09.004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

LI, GUOPING, WEIREN XU, CHAOJUN ZHANG, JIANWU WANG, and CHENGBU LIU. "THEORETICAL STUDY ON THE INTERNAL ROTATION OF NITROTYL OF BENZALDOXIMES." Journal of Theoretical and Computational Chemistry 05, no. 01 (2006): 111–20. http://dx.doi.org/10.1142/s0219633606002088.

Full text

Abstract:

The internal rotations of nitrotyl around the bond C–C in Z- and E-benzaldoximes and their various substituted species have been investigated theoretically by the method of density functional theory (DFT) at the B3LYP/6-31G* level. The corresponding rotation transition states have been optimized. The potential barriers and the rates of the internal rotations of various species have been calculated. The rotation barrier of Z-benzaldoxime is lower than that of E-isomer. The para-substitution has only a small influence on the rotation barriers. The conjugations are consolidated in the acidic and basic species of both Z- and E-isomers. The experimental NMR spectrums of Z- and E-benzaldoxime are explained based on the calculation results.

APA, Harvard, Vancouver, ISO, and other styles

8

Ullah, Rooh, Muhammad Fahim, and Muhammad Nouman. "Joint Shear Deformation and Beam Rotation in RC Beam-Column Eccentric Connections." Civil Engineering Journal 7, no. 2 (2021): 236–52. http://dx.doi.org/10.28991/cej-2021-03091650.

Full text

Abstract:

This paper discusses joint shear deformation and beam rotation for RC beam-column eccentric connections. Two eccentric connections were designed according to ACI 318-14 and ACI-352 and their half scaled models were constructed sequentially to introduce a cold joint at the beam column interface. Specimen having eccentricity equal to bc/8 (12.5% of column width) and bc/4 (25% of column width) were named as specimen 1 and specimen 2 respectively. The specimens were tested under quasi static full cyclic loading. The results are presented in the form of beam rotation versus drift and beam rotation versus lateral load plots. In addition, joint shear deformation versus drift is also plotted for both specimens. Careful observation of the damage pattern revealed that bond slip occurred at 2.5% drift in both specimens with no yielding of beam longitudinal bars in the joint core due to the presence of construction joint. An increase in out of plane rotation was observed with increase in eccentricity. However, in plane rotation was more in specimen 1 as compared to specimen 2, primarily due to negligible out of plane rotations. Furthermore, joint shear deformation increased with increase in eccentricity. However, it was negligible due to slab contribution as well as bond slippage with minimum load transfer to the joint core. It is concluded that bond slippage is the principal failure pattern whereas out of plan rotation increases with eccentricity without significant contribution to the final failure pattern. Doi: 10.28991/cej-2021-03091650 Full Text: PDF

APA, Harvard, Vancouver, ISO, and other styles

9

Colebrook, Lawrence D. "A molecular mechanics study of conformational isomerism in 1- and 3-aryl hydantoins and 3-aryl-2-thiohydantoins." Canadian Journal of Chemistry 69, no. 12 (1991): 1957–63. http://dx.doi.org/10.1139/v91-281.

Full text

Abstract:

Energy profiles for internal rotation about the C—N pivot bond in a series of 1- and 3-aryl hydantoins and 3-aryl-2-thiohydantoins have been computed using the MMX molecular mechanics force field. Rotational ground and transition states have been identified and their energies calculated. Conformational preferences of diastereomeric rotamers have been investigated. Computed rotational energy barriers generally are within ± 2 kcal/mol of the experimentally determined values. Key words: conformational isomerism, hindered rotation, hydantoins, thiohydantoins, molecular mechanics.

APA, Harvard, Vancouver, ISO, and other styles

10

Look, Kai, and Robert K. Norris. "Formation by SRN1 Reactions and 1H N.M.R. Properties of Sterically Encumbered 2,4,6-Trialkylphenyl p-Nitrobenzyl Sulfides." Australian Journal of Chemistry 52, no. 11 (1999): 1077. http://dx.doi.org/10.1071/ch99080.

Full text

Abstract:

Sterically hindered p-nitrobenzylic chlorides (1) and (2) react with the sodium salts of 2,4,6-trialkylbenzenethiols (3a)–(5a) by the SRN1 reaction to give good yields of the corresponding p-nitrobenzylic aryl sulfides (6)–(10). For example, the reaction of sodium 2,4,6-triisopropylbenzenethiolate (4b) with α-t-butyl-a-methyl-p-nitrobenzyl chloride (2) gives the sulfide (10) in over 80% yield after 2 h at room temperature in Me2SO. Only in reactions involving 2,4,6-tri-t-butylbenzenethiol (5a) are low yields or failed reactions encountered. Qualitative examination of the dynamic nuclear magnetic resonance spectra of the sulfides prepared in these reactions shows that up to three restricted rotational phenomena can be identified. These are rotation about the benzylic-carbon to p-nitrophenyl ring bond, rotation about the sulfur to aromatic ring bond, and rotation about the bond joining the t-butyl group to the benzylic carbon. The last phenomenon produces, in the sulfide (9), the relatively rare and unusual situation wherein the t-butyl group appears as three distinct methyl resonances at low temperatures.

APA, Harvard, Vancouver, ISO, and other styles

11

Jones, W. J. "High-resolution Raman spectroscopy of gases and the determination of molecular bond lengths." Canadian Journal of Physics 78, no. 5-6 (2000): 327–90. http://dx.doi.org/10.1139/p00-041.

Full text

Abstract:

This review highlights the developments that have taken place in the field of high-resolution Raman spectroscopy of gases from the pioneering studies of Stoicheff and Welsh in the early fifties to the present day. This period has seen major changes in the methods that have been employed for investigating pure rotation and vibration-rotation spectra from these initial studies with Hg excitation through to the deployment of laser sources for incoherent Raman scattering at enhanced sensitivity, and the subsequent development of the techniques of nonlinear Raman spectroscopy at resolutions of ~10-3 cm-1. A central theme in this review is the measurement of accurate rotational constants for nonpolar molecules that have then been employed for the determination of molecular geometries and bond lengths. The studies by Stoicheff of the pure rotational spectra of a wide range of linear and symmetric-top molecules provided an extensive data base that served to supplement bond-length determinations from other methods and enabled him to correlate CC and CH bond length variations in noncyclic compounds with changes in their environment. The discovery of laser sources in the sixties provided exciting new opportunities for the examination of pure rotation and vibration-rotation spectra at enhanced resolution and sensitivity and broadened dramatically the scope of the field. Apart from the improvements in the incoherent scattering methods afforded by these new sources, the discovery of a range of new nonlinear Raman phenomena, a field in which Stoicheff made equally important contributions, led to the creation of a range of new coherent nonlinear Raman methods that have been widely employed for the study of all rotor classes. Representative examples of the many investigations performed with the various spectroscopic methods over this period are given, together with the results of the structure determinations achieved from the analyses of the rotational spectra.PACS Nos.: 33.20Fb, 36.20.Hb

APA, Harvard, Vancouver, ISO, and other styles

12

Barrows, Susan E., and Thomas H. Eberlein. "Understanding Rotation about a C=C Double Bond." Journal of Chemical Education 82, no. 9 (2005): 1329. http://dx.doi.org/10.1021/ed082p1329.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Jung, Taesub, Hee-Jin Do, Jongwoo Son, et al. "Hindered C N bond rotation in triazinyl dithiocarbamates." Journal of Molecular Structure 1152 (January 2018): 215–22. http://dx.doi.org/10.1016/j.molstruc.2017.09.063.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Huggins, Michael T., Tanay Kesharwani, Jonathan Buttrick, and Christopher Nicholson. "Variable Temperature NMR Experiment Studying Restricted Bond Rotation." Journal of Chemical Education 97, no. 5 (2020): 1425–29. http://dx.doi.org/10.1021/acs.jchemed.0c00057.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Kendelewicz, T., J. E. Klepeis, J. C. Woicik, et al. "Large-angle bond-rotation relaxation for CdTe(110)." Physical Review B 51, no. 16 (1995): 10774–78. http://dx.doi.org/10.1103/physrevb.51.10774.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Bragg, Ryan A., Jonathan Clayden, Gareth A. Morris, and Jennifer H. Pink. "Stereodynamics of Bond Rotation in Tertiary Aromatic Amides." Chemistry - A European Journal 8, no. 6 (2002): 1279–89. http://dx.doi.org/10.1002/1521-3765(20020315)8:6<1279::aid-chem1279>3.0.co;2-7.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Collins, Terrence J., and José M. Workman. "Amides Nonplanar Solely by CN Bond Rotation." Angewandte Chemie International Edition in English 28, no. 7 (1989): 912–14. http://dx.doi.org/10.1002/anie.198909121.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Penner, Glenn H., Baiyi Zhao, and Kenneth R. Jeffrey. "Molecular Dynamics in the Solid Trimethylamine-Borane Complex: A Deuterium NMR Study." Zeitschrift für Naturforschung A 50, no. 1 (1995): 81–89. http://dx.doi.org/10.1515/zna-1995-0111.

Full text

Abstract:

Abstract The molecular dynamics of solid (CH3)3NBH3 is investigated by deuterium NMR spectroscopy. Variable temperature lineshape analyses yield activation energies of 27 ± 3, 19 ± 2, and 12.5 ± 2 kJ/mol for -CH3, -N(CH3)3 and -BH3 rotation, respectively. Analysis of the temperature depen dence of the spin-lattice relaxation times, T1 , gives activation energies of 33 ± 3, 15 ± 1.5, and 14 ± 1.5 kJ/mol, respectively. Direct comparison of rotational exchange rates (from lineshape simu lations) an of rotational correlation times (from T1 analyses) for -N(CH3)3 and -BH3 rotation indicate that the two motions are correlated in solid (CH3)3NBH3 and together constitute a whole molecule reorientation about the N-B bond. This is supported by an internal rotational barrier of 18.0 kJ/mol for-BH3 rotation, obtained from ab initio molecular orbital calculations at the MP2/6-31G* level.

APA, Harvard, Vancouver, ISO, and other styles

19

Grossner, Ulrike, Jürgen Furthmüller, and Friedhelm Bechstedt. "Bond-rotation versus bond-contraction relaxation of (110) surfaces of group-III nitrides." Physical Review B 58, no. 4 (1998): R1722—R1725. http://dx.doi.org/10.1103/physrevb.58.r1722.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Marshall, R. Andrew, Magdalena Dorywalska, and Joseph D. Puglisi. "Irreversible chemical steps control intersubunit dynamics during translation." Proceedings of the National Academy of Sciences 105, no. 40 (2008): 15364–69. http://dx.doi.org/10.1073/pnas.0805299105.

Full text

Abstract:

The ribosome, a two-subunit macromolecular machine, deciphers the genetic code and catalyzes peptide bond formation. Dynamic rotational movement between ribosomal subunits is likely required for efficient and accurate protein synthesis, but direct observation of intersubunit dynamics has been obscured by the repetitive, multistep nature of translation. Here, we report a collection of single-molecule fluorescence resonance energy transfer assays that reveal a ribosomal intersubunit conformational cycle in real time during initiation and the first round of elongation. After subunit joining and delivery of correct aminoacyl-tRNA to the ribosome, peptide bond formation results in a rapid conformational change, consistent with the counterclockwise rotation of the 30S subunit with respect to the 50S subunit implied by prior structural and biochemical studies. Subsequent binding of elongation factor G and GTP hydrolysis results in a clockwise rotation of the 30S subunit relative to the 50S subunit, preparing the ribosome for the next round of tRNA selection and peptide bond formation. The ribosome thus harnesses the free energy of irreversible peptidyl transfer and GTP hydrolysis to surmount activation barriers to large-scale conformational changes during translation. Intersubunit rotation is likely a requirement for the concerted movement of tRNA and mRNA substrates during translocation.

APA, Harvard, Vancouver, ISO, and other styles

21

Liao, Zhaoliang, Nicolas Gauquelin, Robert J. Green, et al. "Metal–insulator-transition engineering by modulation tilt-control in perovskite nickelates for room temperature optical switching." Proceedings of the National Academy of Sciences 115, no. 38 (2018): 9515–20. http://dx.doi.org/10.1073/pnas.1807457115.

Full text

Abstract:

In transition metal perovskites ABO3, the physical properties are largely driven by the rotations of the BO6 octahedra, which can be tuned in thin films through strain and dimensionality control. However, both approaches have fundamental and practical limitations due to discrete and indirect variations in bond angles, bond lengths, and film symmetry by using commercially available substrates. Here, we introduce modulation tilt control as an approach to tune the ground state of perovskite oxide thin films by acting explicitly on the oxygen octahedra rotation modes—that is, directly on the bond angles. By intercalating the prototype SmNiO3 target material with a tilt-control layer, we cause the system to change the natural amplitude of a given rotation mode without affecting the interactions. In contrast to strain and dimensionality engineering, our method enables a continuous fine-tuning of the materials’ properties. This is achieved through two independent adjustable parameters: the nature of the tilt-control material (through its symmetry, elastic constants, and oxygen rotation angles), and the relative thicknesses of the target and tilt-control materials. As a result, a magnetic and electronic phase diagram can be obtained, normally only accessible by A-site element substitution, within the single SmNiO3 compound. With this unique approach, we successfully adjusted the metal–insulator transition (MIT) to room temperature to fulfill the desired conditions for optical switching applications.

APA, Harvard, Vancouver, ISO, and other styles

22

Gao, Shan, and Seik Weng Ng. "2-[(2-Hydroxybenzyl)amino]pyrazinium perchlorate–2-[(pyrazin-2-ylamino)methyl]phenol (1/1)." Acta Crystallographica Section E Structure Reports Online 68, no. 8 (2012): o2475. http://dx.doi.org/10.1107/s1600536812031558.

Full text

Abstract:

In the crystal structure of the title co-crystal, C11H12N3O+·ClO4−·C11H11N3O, the perchlorate ion is disordered about a twofold rotation axis with the Cl atom located on the twofold rotation axis; the 2-[(2-hydroxybenzyl)amino]pyrazinium cation and the neutral 2-[(pyrazin-2-ylamino)methyl]phenol molecule are disordered about the rotation axis in a 1:1 ratio. These two are connected by a pyrazine–pyrazine N1—H...N4hydrogen bond. The cation, whose two aromatic rings are twisted along the –CH2—NH– bond by 76.8 (1)°, is a hydrogen-bond donor to the perchlorate ion through the N atom of this link.

APA, Harvard, Vancouver, ISO, and other styles

23

Gascooke, Jason R., and Warren D. Lawrance. "The Case for Methyl Group Precession Accompanying Torsional Motion." Australian Journal of Chemistry 73, no. 8 (2020): 775. http://dx.doi.org/10.1071/ch19469.

Full text

Abstract:

For molecules containing a methyl group, high precision fits of rotational line data (microwave spectra) that encompass several torsional states require considerably more constants than are required in comparable rigid molecules. Many of these additional terms are ‘torsion-rotation interaction’ terms, but their precise physical meaning is unclear. In this paper, we explore the physical origins of many of these additional terms in the case where the methyl group is attached to a planar frame. We show that torsion-vibration coupling, which has been observed in toluene and several substituted toluenes, provides the dominant contribution to a number of the torsion-rotation constants in toluene. It is further demonstrated that this coupling is intimately related to precession of the methyl group. A number of the constants required in the high resolution fits of rotational line data are shown to arise as a natural consequence of methyl precession. By considering several molecules whose rotational line spectra have been fit to high precision, we demonstrate that the experimental evidence is consistent with the occurrence of methyl group precession. Quantum chemistry calculations of the optimised molecular structures at key torsional angles provide further evidence that methyl precession occurs. There is both a torsional angle dependent tilt of the Cmethyl-frame bond and of the methyl group principal rotation axis relative to the Cmethyl-frame bond.

APA, Harvard, Vancouver, ISO, and other styles

24

Nithya, C., M. Sithambaresan, S. Prathapan, and M. R. Prathapachandra Kurup. "(2E,7E)-2,7-Bis[(thiophen-2-yl)methylidene]cycloheptanone." Acta Crystallographica Section E Structure Reports Online 70, no. 6 (2014): o722. http://dx.doi.org/10.1107/s1600536814011866.

Full text

Abstract:

The whole molecule of the title compound, C17H16OS2, is generated by two-fold rotational symmetry. The carbonyl C and O atoms of the cycloheptanone ring lie on the twofold rotation axis which bisects the opposite –CH2–CH2– bond of the ring. The molecule exists in anE,Econformation with respect to the C=C double bond. The cycloheptanone ring exhibits a twisted chair conformation and its mean plane makes a dihedral angle of 50.12 (19)° with the planes of the thiophene rings. The two S atoms are in anantiarrangement with respect the carbonyl O atom and the dihedral angle between the two thiophene ring planes is 69.38 (7)°. In the molecule, there are two intramolecular C—H...S hydrogen bond, formingS(6) ring motifs. In the crystal, inversion dimers are generatedviapairs of C—H...O hydrogen bonds. These dimers are interconnected by another interaction of the same kind with a neighbouring molecule, forming a molecular chain along thec-axis direction.

APA, Harvard, Vancouver, ISO, and other styles

25

Baddeley, Thomas C., Iain G. Davidson, Christopher Glidewell, John N. Low, Janet M. S. Skakle та James L. Wardell. "Supramolecular structures of substituted α,α′-trehalose derivatives". Acta Crystallographica Section B Structural Science 60, № 4 (2004): 461–71. http://dx.doi.org/10.1107/s0108768104010912.

Full text

Abstract:

The structures of five substituted α,α′-trehalose trehalose derivatives have been determined, and these are compared with those of four previously published analogues. In 2,2′,3,3′,4,4′-hexaacetato-6,6′-bis-O-methylsulfonyl-α,α′-trehalose, C26H38O21S2, where the molecules lie across twofold rotation axes in the space group C2, a single C—H...O=S hydrogen bond links the molecules into sheets. 2,2′,3,3′,4,4′-Hexaacetato-6,6′-bis-O-(4-toluenesulfonyl)-α,α′-trehalose, C38H46O21S2, crystallizes with Z′ = 2 in the space group P212121 and a combination of three C—H...O hydrogen bonds, each having a carbonyl O atom as an acceptor, and a C—H...π(arene) hydrogen bond link the molecules into a three-dimensional framework. 2,2′,3,3′,4,4′-Hexaacetato-6,6′-diazido-α,α′-trehalose, C24H32N6O15, crystallizes as a partial ethanol solvate and three C—H...O hydrogen bonds link the substituted trehalose molecules into a three-dimensional framework. In 2,2′,3,3′-tetraacetato-6,6′-bis(N-acetylamino)-α,α′-trehalose dihydrate, C24H36N2O15·2H2O, the substituted trehalose molecules lie across twofold rotation axes in the space group P21212 and a three-dimensional framework is generated by the combination of O—H...O and N—H...O hydrogen bonds. The diaminotrehalose molecules in 6,6′-diamino-α,α′-trehalose dihydrate, C12H24N2O9.2(H2O), lie across twofold rotation axes in the space group P43212: a single O—H...N hydrogen bond links the trehalose molecules into sheets, which are linked into a three-dimensional framework by O—H...O hydrogen bonds.

APA, Harvard, Vancouver, ISO, and other styles

26

Brownstein, S., and J. Roovers. "Calculation of barriers to rotation in PEEK and some of its substituted derivatives." Canadian Journal of Chemistry 75, no. 9 (1997): 1225–28. http://dx.doi.org/10.1139/v97-147.

Full text

Abstract:

Barriers to rotation have been calculated by molecular mechanics, using the force field MM+, for a fragment of PEEK and its methyl, ethyl, isopropyl, tert-butyl and di-tert-butyl, substituted derivatives. The barrier for the nearer C—O bond increases from 2.0 kcal/mol in KEEK to 16 kcal/mol in dibutyl substituted KEEK as the bulkiness of the substituent increases. The rotation barrier of the further C—O bond is not affected by the substituent. Keywords: rotation barriers, PEEK, molecular mechanics.

APA, Harvard, Vancouver, ISO, and other styles

27

Lee, Gun-Do, Alex W. Robertson, Sungwoo Lee, et al. "Direct observation and catalytic role of mediator atom in 2D materials." Science Advances 6, no. 24 (2020): eaba4942. http://dx.doi.org/10.1126/sciadv.aba4942.

Full text

Abstract:

The structural transformations of graphene defects have been extensively researched through aberration-corrected transmission electron microscopy (AC-TEM) and theoretical calculations. For a long time, a core concept in understanding the structural evolution of graphene defects has been the Stone-Thrower-Wales (STW)–type bond rotation. In this study, we show that undercoordinated atoms induce bond formation and breaking, with much lower energy barriers than the STW-type bond rotation. We refer to them as mediator atoms due to their mediating role in the breaking and forming of bonds. Here, we report the direct observation of mediator atoms in graphene defect structures using AC-TEM and annular dark-field scanning TEM (ADF-STEM) and explain their catalytic role by tight-binding molecular dynamics (TBMD) simulations and image simulations based on density functional theory (DFT) calculations. The study of mediator atoms will pave a new way for understanding not only defect transformation but also the growth mechanisms in two-dimensional materials.

APA, Harvard, Vancouver, ISO, and other styles

28

Ma, Jin-Shi, and David A. Lightner. "Restricted bond rotation and fluorescence following photoexcitation of dipyrrinones." Tetrahedron 47, no. 23 (1991): 3719–26. http://dx.doi.org/10.1016/s0040-4020(01)80898-x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Kang, Young Kee, and Hae Sook Park. "Internal rotation about the C–N bond of amides." Journal of Molecular Structure: THEOCHEM 676, no. 1-3 (2004): 171–76. http://dx.doi.org/10.1016/j.theochem.2004.01.024.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Vargas, Rubicelia, Jorge Garza, David Dixon, and Benjamin P. Hay. "C(sp2)−C(Aryl) Bond Rotation Barrier inN-Methylbenzamide." Journal of Physical Chemistry A 105, no. 4 (2001): 774–78. http://dx.doi.org/10.1021/jp003340f.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Ishida, Hiroyuki, Yoshihiro Kubozono, Setsuo Kashino, and Ryuichi Ikeda. "Structural Parameters and Internal Rotational Barriers of tert-Butylammonium Ion: AM1 and ab initio Calculations." Zeitschrift für Naturforschung A 47, no. 12 (1992): 1255–56. http://dx.doi.org/10.1515/zna-1992-1215.

Full text

Abstract:

Semiempirical and ab initio MO calculations were performed to estimate the structural parameters of tert-butylammonium ion and its potential energies for the internal rotation of the CH3 and NH3+ groups. The barrier height for the rotation of NH3+ was found to be lower than for that of CH3 , corresponding to the C - N bond being longer than the C - C bond.

APA, Harvard, Vancouver, ISO, and other styles

32

Zhao, Sha-Sha, Qiong Su, Zhi-Hong Peng, and De-Lie An. "2,6-Bis(4-methoxyphenyl)-1,4-dithiine." Acta Crystallographica Section E Structure Reports Online 70, no. 2 (2014): o137. http://dx.doi.org/10.1107/s1600536814000397.

Full text

Abstract:

The title molecule, C18H16O2S2, reveals crystallographic twofold rotation symmetry (with both S atoms lying on the axis) and one half-molecule defines an asymmetric unit. The dithiine ring is in a boat conformation. The aromatic ring and the C=C bond are nearly coplanar, with small torsion angles of −171.26 (19) and 8.5 (3)°. The two S—C bond lengths [1.7391 (19) and 1.7795 (18) Å] are shorter than single C—S bonds and longer than analogous C=S double bonds, which indicates a certain degree of conjugation between the lone pair on the S atom and π electrons of the C=C bond. The crystal packing only features van der Waals interactions.

APA, Harvard, Vancouver, ISO, and other styles

33

JÍMENEZ-FABIAN and A. F. JALBOUT. "THE ORIGIN OF THE ROTATIONAL BARRIER IN DIMETHYL ETHER AND DIMETHYL SULFIDE: A THEORETICAL STUDY." Journal of Theoretical and Computational Chemistry 06, no. 03 (2007): 421–34. http://dx.doi.org/10.1142/s0219633607003210.

Full text

Abstract:

The torsional potential function for methyl rotation in dimethyl ether (DME) and dimethyl sulfide (DMS) has been determined by utilizing ab initio (Hartree–Fock and MP2) and density functional theory (B3LYP, B3P86, and B3PW91) methods along with several basis sets. Natural bond orbital (NBO) analysis was also applied to investigate the origin of the rotational barrier.

APA, Harvard, Vancouver, ISO, and other styles

34

Ernst, Ludger, Thomas Rieck, and Mark Soliven. "Article." Canadian Journal of Chemistry 77, no. 11 (1999): 1697–706. http://dx.doi.org/10.1139/v99-130.

Full text

Abstract:

Schaefer's "J method" was employed to show that 2-cyclopropyl-1,3-dimethylbenzene (5) in solution prefers the perpendicular conformation in which the torsional angle Θ between the C(1)-H bond of the cyclopropyl group and the plane of the benzene ring is 90°. This is opposed to the situation in cyclopropylbenzene (3) where the bisected conformer (Θ = 0°) prevails. From the value of -0.85 ± 0.01 Hz for 6J(H-alpha,H-para) in 5 (for solutions in CS2 and in acetone) a barrier to rotation about the cyclopropyl-aryl bond of 6.4 kJ/mol can be derived if a predominantly two-fold potential and a vanishing 6J(H,H) for Θ = 0° are assumed. The introduction of the two ortho-methyl groups into 3 thus effectively interchanges the ground and transition state conformations of the internal rotation. This effect is well reproduced by ab initio (STO-3G and 6-31G*) and semiempirical (AM1) molecular orbital computations. The preference for the perpendicular conformation of an ortho-disubstituted cyclopropyl substituent was also demonstrated by a dynamic NMR study of 2-cyclopropyl-4-isopropyl-1,3,5-trimethylbenzene (10). Exchange-broadened 1H spectra due to slow rotation of the cyclopropyl group were only obtained near the low-temperature limit of the spectrometer (-140°C), and the barrier to rotation is estimated to lie near 28 kJ/mol (deltaG). MM3 molecular mechanics computations suggest that the rather large increase of the rotational barrier in 10 relative to 5 is caused by the combined buttressing effect of the isopropyl and the 5-methyl groups. The present findings explain why an earlier attempt (in 1970) to determine the rotational barrier in 2-cyclopropyl-1,3,5-trimethylbenzene by dynamic NMR was bound to fail.Key words: conformation, cyclopropylbenzenes, ortho-disubstituted, NMR spectroscopy, rotational barrier.

APA, Harvard, Vancouver, ISO, and other styles

35

Hardhienata, Hendradi, Ignu Priyadi, Bayti Nurjanati, and Husin Alatas. "Third harmonic generation in ZnO semiconductor using the simplified bond hyperpolarizability model." Journal of Nonlinear Optical Physics & Materials 27, no. 03 (2018): 1850025. http://dx.doi.org/10.1142/s021886351850025x.

Full text

Abstract:

We describe the fourth rank tensor and the related third harmonic generation (THG) light intensity profile in a (0002) wurtzite structure using the simplified bond hyperpolarizability model (SBHM). We show that the resulting THG intensity is isotropic e.g., does not depend on the azimuthal rotation angle of the material. Assuming that THG inside wurtzite structures are dominated solely by bulk dipoles, only one fitting parameter in terms of the effective THG hyperpolarizability is required to generate the Rotational Anisotropy THG (RATHG) experiment result.

APA, Harvard, Vancouver, ISO, and other styles

36

Santoso, Nugroho, Bambang Suharnadi, Benidiktus Tulung Prayoga, and Lilik Dwi Setyana. "CHARACTERISTIC OF INTERFACE BIMETAL ALUMINUM-COPPER FOR BIMETAL BUSHING PRODUCED BY CENTRIFUGAL CASTING." Acta Metallurgica Slovaca 27, no. 1 (2021): 28–31. http://dx.doi.org/10.36547/ams.27.1.756.

Full text

Abstract:

Bimetallic is a type of metal composite that combines two metals that form a metallurgical bond. The manufacture of bimetallic bushings by centrifugal casting has not been developed much. Recently, there is no recommendation yet for optimum temperature and speed of rotation to produce bimetallic bushings. The research was conducted to determine the rotation of the mold in centrifugal casting so as to produce a well-integrated interface. The materials used are aluminum and copper. Aluminum was melted at 750 °C, while copper was melted at 1200 °C. Molten metal was pouring alternately. First, aluminum was poured into the mold, and then after the aluminum temperature reached 400º C, copper was poured into the mold to form a bushing aluminum-copper bimetallic. The molten metal was poured into a rotating sand mold with a constant filling speed of about 0.15 kg s-1. The variations of the rotational speed of the mold were 250, 300, and 350 rpm. The result shows that the interface’s width increases as the mold rotation increases during the pouring process. Interface hardness and wear are increased compared to the base metal. Hence, centrifugal casting with 350 rpm is recommended for aluminum-copper bimetal bushing applications.

APA, Harvard, Vancouver, ISO, and other styles

37

Samolová, Erika, та Jan Fábry. "Poly[[tetradecakis(μ-propionato)heptabarium] propionic acid monosolvate tetrahydrate]". Acta Crystallographica Section E Crystallographic Communications 76, № 2 (2020): 264–69. http://dx.doi.org/10.1107/s2056989020000924.

Full text

Abstract:

The title compound, {[Ba7(C3H5O2)14]·0.946C3H6O2·4H2O} n , is represented by a metal–organic framework structure that is held together by Ba—O—Ba bonds, as well as by O—H...O hydrogen bonds of moderate strength. The structure comprises of four independent Ba2+ cations (one of which is situated on a twofold rotation axis), seven independent propionate and two independent water molecules. The bond-valence sums of all the cations indicate a slight overbonding. There is also an occupationally, as well as a positionally disordered propionic acid molecule present in the structure. Its occupation is slightly lower than the full occupation while the disordered molecules occupy two positions related by a rotation about a twofold rotation axis. In addition, the methyl group in the symmetry-independent propionic acid molecule is also disordered, and occupies two positions. Each propionic acid molecule coordinates to just one cation from a pair of symmetry-equivalent Ba2+ sites and is simultaneously bonded by an O—H...Opropionate hydrogen bond. This means that on a microscopic scale, the coordination number of the corresponding Ba2+ site is either 9 or 10. The methyl as well as hydroxy hydrogen atoms of the disordered propionic acid molecule were not determined.

APA, Harvard, Vancouver, ISO, and other styles

38

Laidig, Keith E., and Lynn M. Cameron. "What happens to formamide during C—N bond rotation? Atomic and molecular energetics and molecular reactivity as a function of internal rotation." Canadian Journal of Chemistry 71, no. 6 (1993): 872–79. http://dx.doi.org/10.1139/v93-116.

Full text

Abstract:

We investigate the energetics of rotation about the C—N bond in formamide at the molecular and atomic levels using the HF/6-31G**//HF/6-31G** level of theory. At the molecular level, the barrier to rotation results from a decrease in overall attractive energies upon rotation away from the planar conformation, primarily due to the lengthening of the C—N bond. At the atomic level, the barrier is due to the loss in interatomic attraction between the nitrogen and its bonded neighbors. We investigate the susceptibility of formamide to electrophilic attack at nitrogen and oxygen as well as nucleophilic attack at carbonyl carbon as a function of C—N bond rotation using the Laplacian model of reactivity. The model predicts the susceptibility to nucleophilic attack at carbonyl carbon to reach a maximum with a O—C—N—H torsional angle of 60°. As a mimic of solvent fields, we investigate the effect of solvation upon these predictions with the application of homogeneous electric fields. This geometry–reactivity relationship is related to proposed models of activation in the enzymatic catalysis of peptides.

APA, Harvard, Vancouver, ISO, and other styles

39

Marekha, Bogdan A., and Johannes Hunger. "Hydrophobic pattern of alkylated ureas markedly affects water rotation and hydrogen bond dynamics in aqueous solution." Physical Chemistry Chemical Physics 21, no. 37 (2019): 20672–77. http://dx.doi.org/10.1039/c9cp04108g.

Full text

Abstract:

Femtosecond infrared spectroscopies reveal the substitution pattern of alkylated ureas to be decisive for hydrogen-bond strengths, water rotation, and hydrogen bond fluctuation in the hydration shell.

APA, Harvard, Vancouver, ISO, and other styles

40

Li, Zhi. "3-Oxapentane-1,5-diyl dicarbamate." Acta Crystallographica Section E Structure Reports Online 68, no. 4 (2012): o1171. http://dx.doi.org/10.1107/s1600536812011981.

Full text

Abstract:

The complete molecule of the title compound, C6H12N2O5, is generated by a rotation about a twofold axis. The conformation along the bond sequence linking the two amino groups istrans-trans-(+)gauche-trans-trans. In the crystal, N—H...O hydrogen bonds link the molecules into a three-dimensional supramolecular architecture.

APA, Harvard, Vancouver, ISO, and other styles

41

Cati, Dilovan S., and Helen Stoeckli-Evans. "Crystal structure of a pyrazine-2,3-dicarboxamide ligand and of its silver(I) nitrate complex, a three-dimensional coordination polymer." Acta Crystallographica Section E Crystallographic Communications 73, no. 6 (2017): 798–803. http://dx.doi.org/10.1107/s2056989017006387.

Full text

Abstract:

The title ligand, C18H16N6O2·2H2O (L1) [N2,N3-bis(pyridin-4-ylmethyl)pyrazine-2,3-dicarboxamide], crystallized as a dihydrate. The molecule is U-shaped with the carboxamide groups beingcisto one another, making a dihedral angle of 81.6 (5)°. The terminal pyridine rings are inclined to one another by 58.5 (4)°. There is an intramolecular N—H...Npyrazinehydrogen bond present, forming anS(5) ring motif. In the crystal, adjacent molecules are linked by N—H...Ocarboxamidehydrogen bonds, forming a chain along [001]. A chain of hydrogen-bonded water molecules is linked to the chain of (L1) molecules by O—H...N hydrogen bonds, forming columns propagating along thecaxis. The columns are linked by C—H...O and C—H...N hydrogen bonds, forming a three-dimensional supramolecular structure. The reaction of ligand (L1) with silver(I) nitrate led to the formation of a new three-dimensional coordination polymer, {[Ag(C18H16N6O2)]NO3}n, poly[[[μ4-N2,N3-bis(pyridin-4-ylmethyl)pyrazine-2,3-dicarboxamide]silver(I)] nitrate] (I). The asymmetric unit is composed of half of one silver ion, located on a twofold rotation axis, half a ligand molecule and half a positionally disordered nitrate anion located about a twofold rotation axis. The full molecule of the ligand is generated by twofold rotational symmetry, with this twofold axis bisecting the Car—Carbonds of the pyrazine ring and the Ag—Ag bond. The carboxamide groups are nowtransto one another, making a dihedral angle of 65.8 (4)°. The two terminal pyridine rings are inclined to one another by 6.6 (3)°. Two ligands wrap around an Ag—Ag bond of 3.1638 (11) Å, forming a figure-of-eight-shaped complex molecule. Each silver ion is coordinated by two pyridine N atoms and by two carboxamide O atoms of neighbouring molecules, hence forming a three-dimensional framework. The nitrate anion is linked to the framework by N—H...O and C—H...O hydrogen bonds.

APA, Harvard, Vancouver, ISO, and other styles

42

Huang, Shih-Hung, Yeo-Wan Chiang, and Jin-Long Hong. "Luminescent polymers and blends with hydrogen bond interactions." Polymer Chemistry 6, no. 4 (2015): 497–508. http://dx.doi.org/10.1039/c4py01146e.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Harcourt, Richard D. "Valence bond studies of the barrier to rotation around the NN bond of N2O4." Chemical Physics Letters 218, no. 1-2 (1994): 175–82. http://dx.doi.org/10.1016/0009-2614(93)e1429-k.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Zhang, Song, Lian Wang, Miaomiao Zhou, and Bing Zhang. "Evidence for Free Rotation Restriction of Unsaturated Bond in Aggregation-Induced Emission." EPJ Web of Conferences 205 (2019): 09014. http://dx.doi.org/10.1051/epjconf/201920509014.

Full text

Abstract:

We experimentally demonstrate that that nonradiative process, which competes with radiative decay, involves two main stages, namely the restricted intramolecular rotation and internal conversion process. The free rotation restriction of the unsaturated bond at the excited state is the key factor for AIE effects.

APA, Harvard, Vancouver, ISO, and other styles

45

Yu, Hong, Yue-Bao Jin, Yong-Kang Chang, and Ke-Wei Lei. "2-[(E)-(4-Fluorobenzyl)iminomethyl]-6-methoxyphenol." Acta Crystallographica Section E Structure Reports Online 68, no. 8 (2012): o2401. http://dx.doi.org/10.1107/s1600536812027419.

Full text

Abstract:

In the title Schiff base, C15H14FNO2, the dihedral angle between the benzene rings is 53.32 (8)°. In the crystal, molecules related by a twofold rotation axis are linked by pairs of C—H...O hydrogen bonds into dimers withR22(18) ring motifs. An intramolecular O—H...N hydrogen bond is also observed.

APA, Harvard, Vancouver, ISO, and other styles

46

Breit, Nora C., Tibor Szilvási, and Shigeyoshi Inoue. "Facile rotation around a silicon–phosphorus double bond enabled through coordination to tungsten." Chemical Communications 51, no. 56 (2015): 11272–75. http://dx.doi.org/10.1039/c5cc04247j.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Schaefer, Ted, and Glenn H. Penner. "The conformational properties of some phenyl esters. Molecular orbital and nuclear magnetic resonance studies." Canadian Journal of Chemistry 65, no. 9 (1987): 2175–78. http://dx.doi.org/10.1139/v87-363.

Full text

Abstract:

Extensive, geometry-optimized, STO-3G MO computations on phenyl formate imply a strongly nonplanar Z conformer (C=O bond cis to the phenyl group) at ambient temperatures. The internal barrier to rotation about the C(1)—O bond in this conformer is computed as V/kJ mol−1 = (−5.17 ± 0.27) sin2 θ − (2.42 ± 0.27) sin2 2θ, θ being zero for the planar conformer; the twofold is nearly twice as large as the fourfold component. The expectation value of θ is 58° at 300 K. The spin–spin coupling constants over six bonds between 13C and I9F nuclei in 4-fluorophenyl formate, acetate, propionate, and isobutyrate, as well as in the 2,6-dichloro-4-fluorophenyl acetate, are adduced as evidence for nonplanar conformers of these molecules. The magnitudes of these six-bond coupling constants are consistent with internal barriers to rotation about the C(1)—O bonds, which are similar in magnitude to those given by the computations on the Z conformer of phenyl formate. The energies of the planar and nonplanar E conformers, as well as the interconversion energies for [Formula: see text] isomerization, are computed. Small amounts of the nonplanar E conformer are predicted at ambient temperatures. The 13C chemical shifts and the one-bond 13C, 19F coupling constants are consistent, respectively, with only minor variations in the conformational behavior of the ester moieties caused by the fluorine substituent and by changes in the structures of these moieties themselves.

APA, Harvard, Vancouver, ISO, and other styles

48

Breedveld, Peter. "Stability of rigid body rotation from a bond graph perspective." Simulation Modelling Practice and Theory 17, no. 1 (2009): 92–106. http://dx.doi.org/10.1016/j.simpat.2008.02.006.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Liu, Shubin. "Origin and Nature of Bond Rotation Barriers: A Unified View." Journal of Physical Chemistry A 117, no. 5 (2013): 962–65. http://dx.doi.org/10.1021/jp312521z.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Roth, Wolfgang R., and Michael Quast. "The Barrier to Rotation about the Double Bond in Methylenecyclopropane." European Journal of Organic Chemistry 1998, no. 5 (1998): 763–68. http://dx.doi.org/10.1002/(sici)1099-0690(199805)1998:5<763::aid-ejoc763>3.0.co;2-f.

Full text

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!