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Journal articles on the topic 'Hyperconjugative effect'

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Published: 5 June 2025

Last updated: 1 August 2025

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1

Wu, Judy I.-Chia, and Paul von Ragué Schleyer. "Hyperconjugation in hydrocarbons: Not just a “mild sort of conjugation”." Pure and Applied Chemistry 85, no. 5 (2013): 921–40. http://dx.doi.org/10.1351/pac-con-13-01-03.

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This article emphasizes two underappreciated aspects of hyperconjugation in hydrocarbons, two-way hyperconjugation and hyperconjugation in tight spaces. Nonplanar polyenes [e.g., cyclooctatetraene (D2d), biphenyl (D2), styrene (C1)], the nonplanar rotational transition states (TSs) of planar polyenes (e.g., perpendicular 1,3-butadiene), as well as the larger nonplanar Hückel or Möbius annulenes, are stabilized by effective σ-electron delocalization (involving either the C–C or C–H bonds) via two-way hyperconjugation. The collective consequence of two-way hyperconjugation in molecules can be ne

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2

HONG, Hu, Zhao-He HUANG, Zheng-Qi CHAI, and Yuan-Jin ZHANG. "Hyperconjugative and Stereoelectronic Effect." University Chemistry 32, no. 1 (2017): 84–105. http://dx.doi.org/10.3866/pku.dxhx201603010.

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3

King, James F., Manqing Li, Allan Zijun Cheng, Vinod Dave та Nicholas C. Payne. "Variation of the ease of α-sulfonyl carbanion formation with the orientation of different β-substituents: Experimental evidence for the generality of negative hyperconjugation as an important substituent effect". Canadian Journal of Chemistry 81, № 6 (2003): 638–46. http://dx.doi.org/10.1139/v03-015.

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Following up on our previous observation that the rate of formation of a β-alkoxy-substituted α-sulfonyl carbanion depends on the stereochemistry of the alkoxy group, we have found similar behaviour when the β-substituent is R2N, RS, or R3N+. With each substituent, the variation of kN (defined by kN = (kexch)X /(kexch)model) is consistent with an equation of the form log kN = a + b cos2θ, where θ is the H-C-C-X torsion angle. We propose that the a term describes the polar (field plus inductive) effect and the b term the negative hyperconjugative effect of the substituent; we show how the varia

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4

Silla, Josué M., Claudimar J. Duarte, Rodrigo A. Cormanich, Roberto Rittner, and Matheus P. Freitas. "Conformational analysis of 2,2-difluoroethylamine hydrochloride: double gauche effect." Beilstein Journal of Organic Chemistry 10 (April 16, 2014): 877–82. http://dx.doi.org/10.3762/bjoc.10.84.

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The gauche effect in fluorinated alkylammonium salts is well known and attributed either to an intramolecular hydrogen bond or to an electrostatic attraction between the positively charged nitrogen and the vicinal electronegative fluorine atom. This work reports the effect of adding a fluorine atom in 2-fluoroethylamine hydrochloride on the conformational isomerism of the resulting 2,2-difluoroethylamine chloride (2). The analysis was carried out using NMR coupling constants in D2O solution, in order to mimic the equilibrium conditions in a physiological medium, in the gas phase and in implici

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5

Port, Vinicius C., and Rodrigo A. Cormanich. "There and back again: the role of hyperconjugation in the fluorine gauche effect." Physical Chemistry Chemical Physics 23, no. 32 (2021): 17329–37. http://dx.doi.org/10.1039/d1cp02806e.

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The fluorine gauche effect was revisited by comparing the rotational profile of 1,2-difluoroethane (DFE) with several analogues, such as peroxides and dissulfides. Hyperconjugative effects are the most important ones for the gauche preference of DFE.

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6

Zhang, Jianen, Mingjun Chen, Xiaojie Ren, et al. "Effect of conjugation length on fluorescence characteristics of carbon dots." RSC Advances 13, no. 40 (2023): 27714–21. http://dx.doi.org/10.1039/d3ra05031a.

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Fluorescence emission is highly correlated with the conjugation length. The lower aromatic stabilization leads to longer fluorescence wavelength. The influence of sp3 carbon atoms mainly reflects in the hyperconjugative effect.

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7

Martins, Francisco A., Josué M. Silla, and Matheus P. Freitas. "Conformational impact of structural modifications in 2-fluorocyclohexanone." Beilstein Journal of Organic Chemistry 13 (August 24, 2017): 1781–87. http://dx.doi.org/10.3762/bjoc.13.172.

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2-Haloketones are building blocks that combine physical, chemical and biological features of materials and bioactive compounds, while organic fluorine plays a fundamental role in the design of performance organic molecules. Since these features are dependent on the three-dimensional chemical structure of a molecule, simple structural modifications can affect its conformational stability and, consequently, the corresponding physicochemical/biological property of interest. In this work, structural changes in 2-fluorocyclohexanone were theoretically studied with the aim at finding intramolecular

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8

MO, YIRONG, LINGCHUN SONG, WEI WU, ZEXING CAO, and QIANER ZHANG. "ELECTRONIC DELOCALIZATION: A QUANTITATIVE STUDY FROM MODERN AB INITIO VALENCE BOND THEORY." Journal of Theoretical and Computational Chemistry 01, no. 01 (2002): 137–51. http://dx.doi.org/10.1142/s0219633602000099.

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An ab initio spin-free valence bond code called Xiamen-99 has been developed based on an efficient algorithm called paired-permanent-determinant approach, where Hamiltonian and overlap matrix elements are expressed in terms of paired-permanent-determinants. With this tool, we probed the electronic delocalization phenomenon in a few typical examples including benzene, formamide and ethane. Our computations revealed that ab initio valence bond methods are able to estimate the energetic contribution from the delocalization effect to the stabilization of molecules, thus pave the way to illuminate

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9

Chen, XiangJun, Fang Wu, Mi Yan, et al. "Hyperconjugative effect on the electronic wavefunctions of ethanol." Chemical Physics Letters 472, no. 1-3 (2009): 19–22. http://dx.doi.org/10.1016/j.cplett.2009.02.064.

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10

Behrouz, Athena, and Davood Nori-Shargh. "The Importance of the Pauli Exchange-Type Repulsions and Hyperconjugative Interactions on the Conformational Properties of Halocarbonyl Isocyanates and Halocarbonyl Azides." Australian Journal of Chemistry 70, no. 1 (2017): 61. http://dx.doi.org/10.1071/ch16227.

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To gain further insight into the origin of the anomeric relationships in planar open-chain (acyclic) compounds, we examined the effects of the hyperconjugative generalized anomeric effect (HC-GAE), Pauli exchange-type repulsion (PETR), the electrostatic model associated with the dipole–dipole interactions (EM-DDI), and the attractive electrostatic interactions (AEI) between the natural atomic charges (NACs) on the conformational properties of halocarbonyl isocyanates [halogen = F (1), Cl (2), Br (3)] and halocarbonyl azides [halogen = F (4), Cl (5), Br (6)] by means of G3MP2, CCSD, MP2, and B3

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11

R., C. RASTOGI, H. KHAN R., and C. BORTHAKUR R. "A Direct Evidence for Hyperconjugation from Nuclear Overhauser Effect Study." Journal of Indian Chemical Society Vol. 69, Jun 1992 (1992): 310–11. https://doi.org/10.5281/zenodo.6004556.

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Synthetic Organic Chemistry Division, Regional Research Laboratory, Jorhat-785 006 <em>Manuscript received 26 August 1991,  revised 27 march 1992, accepted 30 April 1992</em> Nuclear Overhauser effect studies show that the higher field shift of aromatic proton (2H) in intramolecularly bonded 3-(<em>N</em>,<em>N</em>-dialkylaminomethyl)-4-hydroxyacetophenones is mainly due to a directionally favourable hyperconjugative effect.

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12

Coxon, James M., and D. Quentin McDonald. "The “cieplak effect”: Hyperconjugative interactions in diels alder reactions." Tetrahedron Letters 33, no. 5 (1992): 651–54. http://dx.doi.org/10.1016/s0040-4039(00)92334-7.

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13

Medina, Inmaculada C. Rodriguez, and James R. Hanson. "The Dinitration of Dimethylacetanilides." Journal of Chemical Research 2003, no. 5 (2003): 303–4. http://dx.doi.org/10.3184/030823403103173903.

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The orientation of dinitration of the dimethylacetanilides has been examined by 1H NMR methods and a possible enhancement of the hyperconjugative influence of a methyl group has been considered as an additional factor augmenting the effect of the steric inhibition of resonance on the orientation of substitution.

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14

Coxon, James M., та D. Quentin McDonald. "The “cieplak” effect: hyperconjugative interactions at facially dissymmetric π-systems." Tetrahedron 48, № 16 (1992): 3353–64. http://dx.doi.org/10.1016/0040-4020(92)85011-3.

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15

Nori-Shargh, Davood, Seiedeh Negar Mousavi, Rose Tale, and Hooriye Yahyaei. "Hyperconjugative interactions are the main responsible for the anomeric effect: a direct relationship between the hyperconjugative anomeric effect, global hardness and zero-point energy." Structural Chemistry 27, no. 6 (2016): 1753–68. http://dx.doi.org/10.1007/s11224-016-0791-0.

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16

Tavanaei, Leila, and Davood Nori-Shargh. "New Insights into the Origin of the cis-Configuration Preferences in 1,2-Dihaloethenes: The Importance of the Bonding Orbital Deviations." Australian Journal of Chemistry 71, no. 1 (2018): 1. http://dx.doi.org/10.1071/ch17219.

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The origin of the preferences for the cis-configurations in 1,2-difluoroethene (1), 1,2-dichloroethene (2), and 1,2-dibromoethene (3) were explored by means of the G3MP2, LC-ωPBE and CCSD(T) methods with the 6–311+G** basis set on all atoms, and natural bond orbital interpretation. On the basis of the results obtained, the cis-configurations preferences decrease in going from compound 1 to compound 3. Effectively, the deletions of the hyperconjugative interactions from the Fock matrices of the cis- and trans-configurations of compound 1 lead to the increase of the trans-conformation stability

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17

Cooney, BT, and DAR Happer. "The Baker-Nathan Order: Hyperconjugation or a Solvent Effect?" Australian Journal of Chemistry 40, no. 9 (1987): 1537. http://dx.doi.org/10.1071/ch9871537.

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The electronic effect of alkyl groups attached to an aromatic ring has been determined under varying conditions of electron demand by measuring their influence on the 13C n.rn.r. chemical shifts of the β-carbon of β-substituted styrenes. When the group, is para to the side chain their ability to donate electrons follows the order Me > Et > Pri > But, and, when meta, But > Pri > Et > Me. This order is the same in CCl4, CDCl3, Me2SO and EtOH solvent, the results suggesting that the Baker-Nathan effect is a hyperconjugative rather than solvation phenomenon.

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18

Wang, Ke-dong, Hai-xia Zhang, and Yu-fang Liu. "Ab initioStudy of Hyperconjugative Effect on Electronic Wavefunctions of 2-chloroethanol." Chinese Journal of Chemical Physics 24, no. 4 (2011): 434–38. http://dx.doi.org/10.1088/1674-0068/24/04/434-438.

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19

Craig, DC, MN Paddonrow, and HK Patney. "The Syntheses and Crystal-Structures of Decahydro-5,14:6,13:7,12-Trimethanopentacene and Decahydro-5,14-7,12-Dimethanopentacene: Two Useful Molecules for Investigating Laticyclic Hyperconjugation." Australian Journal of Chemistry 39, no. 10 (1986): 1587. http://dx.doi.org/10.1071/ch9861587.

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The syntheses of decahydro-5,14:6,13:7,12-trimethanopentacene and decahydro-5,14:7,12-dimethanopentacene are described (see Schemes 1 and 2 respectively). Diels -Alder reaction of diene (10) with two equivalents of tetrachlorothiophen 1,1-dioxide (11) gave the adduct (12), which was aromatized to (13) through treatment with base. Reductive dechlorination (Na/ PriOH ) of (13) gave (6). A similar set of reactions performed on (17), itself prepared from cyclohexa-1,4-diene and two equivalents of hexachlorocyclopentadiene (15), gave (7). The crystal structures of (6) and (7) were determined. An in

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20

Mo, Yirong. "Computational evidence that hyperconjugative interactions are not responsible for the anomeric effect." Nature Chemistry 2, no. 8 (2010): 666–71. http://dx.doi.org/10.1038/nchem.721.

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21

Mo, Yirong. "Erratum: Computational evidence that hyperconjugative interactions are not responsible for the anomeric effect." Nature Chemistry 2, no. 9 (2010): 789. http://dx.doi.org/10.1038/nchem.826.

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22

Lecoultre, Jacques, Edgar Heilbronner, Paul Müller, and Domingo Rodriguez. "The influence of fluoro substituents on cyclopropa-benzene, -naphthalene, and -anthracene." Collection of Czechoslovak Chemical Communications 53, no. 10 (1988): 2385–98. http://dx.doi.org/10.1135/cccc19882385.

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The He(Iα) PE spectra of cyclopropabenzene, cyclopropa[b]naphthalene, cyclopropa[b]anthracene, their 1,1-difluoro derivatives and of some of their substituted derivatives have been recorded, analyzed and assigned by correlation with the PE spectra of the parent molecules benzene, naphthalene and anthracene. It is shown that the PE spectroscopic data yield no information about the presence or absence of a Mills-Nixon effect in the molecules investigated. The inductive effect of the bridging CH2 group of the cyclopropeno ring is close to zero, whereas that of the CF2 group leads to positive ioni

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23

Taddei, Ferdinando, and Erich Kleinpeter. "The anomeric effect in substituted cyclohexanes. I. The role of hyperconjugative interactions and steric effect in monosubstituted cyclohexanes." Journal of Molecular Structure: THEOCHEM 683, no. 1-3 (2004): 29–41. http://dx.doi.org/10.1016/j.theochem.2004.06.010.

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24

Fernández, Israel, та Gernot Frenking. "Hyperconjugative Stabilization in Alkyl Carbocations: Direct Estimate of the β-Effect of Group-14 Elements". Journal of Physical Chemistry A 111, № 32 (2007): 8028–35. http://dx.doi.org/10.1021/jp073737k.

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25

Taddei, Ferdinando, and Erich Kleinpeter. "The anomeric effect in substituted cyclohexanes. II. The role of hyperconjugative interactions and steric effect in 1,4-disubstituted cyclohexanes." Journal of Molecular Structure: THEOCHEM 718, no. 1-3 (2005): 141–51. http://dx.doi.org/10.1016/j.theochem.2005.01.003.

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26

Wang, Changwei, Fuming Ying, Wei Wu, and Yirong Mo. "How Solvent Influences the Anomeric Effect: Roles of Hyperconjugative versus Steric Interactions on the Conformational Preference." Journal of Organic Chemistry 79, no. 4 (2014): 1571–81. http://dx.doi.org/10.1021/jo402306e.

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27

PARVEEN, SALMA, SUBOJIT DAS, ASIT K. CHANDRA, and THERESE ZEEGERS-HUYSKENS. "THEORETICAL STUDIES OF HYDROGEN BONDING INTERACTION BETWEEN TRIMETHYLAMINE AND SUBSTITUTED PHENOLS, INFLUENCE OF THE SUBSTITUENTS ON THE HYDROGEN BOND PROPERTIES AND THE VIBRATIONAL SPECTRUM." Journal of Theoretical and Computational Chemistry 07, no. 06 (2008): 1171–86. http://dx.doi.org/10.1142/s0219633608004507.

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Hydrogen bonding interactions between trimethylamine (TMA) and a series of para substituted phenols (X– C 6 H 4 OH , X = H , CH 3, NH 2, Cl , CN , and NO 2) are studied by using density functional theory with the hybrid B3LYP functional and the 6-31++G(d,p) basis set. Both electron donor and acceptor substituents (X) are chosen to study systematically the relation between the proton donor ability of the phenols and the strength of the OH … N hydrogen bond. The effect of hydrogen bonding on spectral and structural parameters and their inter relation are discussed. The natural bond orbital (NBO)

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28

Almogati, Rawan N., Saadullah G. Aziz, and Rifaat Hilal. "Effect of substitution on the optoelectronic properties of dyes for DSSC. A DFT approach." Journal of Theoretical and Computational Chemistry 16, no. 02 (2017): 1750018. http://dx.doi.org/10.1142/s0219633617500183.

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The present work aims at a better and deeper insight into the forces that govern the intramolecular charge transfer (ICT) and photo injection processes in dyes for dye sensitized solar cells (DSSC). The geometry, electronic structure, electron density distribution, and absorption spectra, for a selected donor-[Formula: see text]-acceptor (D-[Formula: see text]-A) dye for DSSC were computed and analyzed at a high level of DFT theory. The coplanar geometry of the studied dye (D1) indicates a strong conjugation which facilitates ICT. NBO analyses reveal that this ICT amounts to 0.8e, which is loc

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29

Shindo, Mitsuru, Kenji Matsumoto, and Kozo Shishido. "Hyperconjugative effect of C–Ge bonds: synthesis of multisubstituted alkenylgermanes via torquoselective olefination of acylgermanes with ynolates." Tetrahedron 63, no. 20 (2007): 4271–77. http://dx.doi.org/10.1016/j.tet.2007.03.048.

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30

Scheidt, Felix, Christian Thiehoff, Gülay Yilmaz, et al. "Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines." Beilstein Journal of Organic Chemistry 14 (May 9, 2018): 1021–27. http://dx.doi.org/10.3762/bjoc.14.88.

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Herein, we describe a catalytic fluorooxygenation of readily accessible N-allylcarboxamides via an I(I)/I(III) manifold to generate 2-oxazolines containing a fluoromethyl group. Catalysis is conditional on the oxidation competence of Selectfluor®, whilst HF serves as both a fluoride source and Brønsted acid activator. The C(sp3)–F bond of the mono-fluoromethyl unit and the C(sp3)–O bond of the ring are aligned in a synclinal relationship thereby engaging in stabilising hyperconjugative interactions with vicinal, electron-rich σ-bonds (σC–C→σ*C–F and σC–H→σ*C–O). This manifestation of the stere

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31

Kucuk, Ceyhun. "Theoretical insights into the structural, spectroscopic, solvent effect, reactivity, NCI, and NLO analyses of 5,7-dichloro-8-hydroxyquinoline-2-carbaldehyde." European Journal of Chemistry 16, no. 1 (2025): 70–82. https://doi.org/10.5155/eurjchem.16.1.70-82.2634.

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In this study, the characterization of the 5,7-dichloro-8-hydroxyquinoline-2-carbaldehyde molecule was carried out by nuclear magnetic resonance (1H and 13C NMR), Fourier transform infrared (FT-IR), ultraviolet-visible (UV-vis) spectroscopy and theoretical calculations in density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The integral equation formalism polarizable continuum (IEFPCM) solvation model was used for ethanol, dimethylsulfoxide (DMSO), and water solvents. The conformation of the molecule was analyzed, and the most stable structure was optimized, a

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32

Wolf, W. M. "X-ray investigations of sulfur-containing fungicides. III. Intramolecular forces governing the conformation of a novel orthorhombic polymorph of benzoylmethyl phenyl sulfone, benzoylmethyl 4-chlorophenyl sulfone and benzoylphenylmethyl phenyl sulfone." Acta Crystallographica Section B Structural Science 57, no. 6 (2001): 806–14. http://dx.doi.org/10.1107/s0108768101016238.

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The crystal and molecular structures of three β-ketosulfones: benzoylmethyl phenyl sulfone (I), benzoylmethyl 4-chlorophenyl sulfone (II) and benzoylphenylmethyl phenyl sulfone (III) have been investigated using X-ray analysis and quantum mechanics ab initio calculations. Compound (I) crystallizes in the monoclinic and orthorhombic crystal systems. The crystal structure of the orthorhombic polymorph has not been reported previously. At room temperature and in the presence of daylight the pale yellow orthorhombic crystals undergo transformation to the stable colourless monoclinic polymorph. Hyp

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33

Zainuri, Dian Alwani, Mundzir Abdullah, Muhamad Fikri Zaini, Hazri Bakhtiar, Suhana Arshad, and Ibrahim Abdul Razak. "Fused ring effect on optical nonlinearity and structure property relationship of anthracenyl chalcone based push-pull chromophores." PLOS ONE 16, no. 9 (2021): e0257808. http://dx.doi.org/10.1371/journal.pone.0257808.

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The Ultraviolet-visible (UV-Vis) spectra indicate that anthracenyl chalcones (ACs) have high maximum wavelengths and good transparency windows for optical applications and are suitable for optoelectronic applications owing to their HOMO–LUMO energy gaps (2.93 and 2.76 eV). Different donor substituents on the AC affect their dipole moments and nonlinear optical (NLO) responses. The positive, negative, and neutral electrostatic potential regions of the molecules were identified using molecular electrostatic potential (MEP). The stability of the molecule on account of hyperconjugative interaction

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34

Andrade, Laize A. F., Lucas A. Zeoly, Rodrigo A. Cormanich, and Matheus P. Freitas. "Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines." Beilstein Journal of Organic Chemistry 15 (February 20, 2019): 506–12. http://dx.doi.org/10.3762/bjoc.15.44.

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The active species of the Ishikawa´s reagent [N,N-diethyl-(1,1,2,3,3,3-hexafluoropropyl)amine] is a fluorinating hexafluoropropylamine used to convert alcohols into alkyl fluorides. On the other hand, it is also an example of model compound useful to probe conformational preferences using spectroscopic information from diastereotopic fluorines. Moreover, the possibility of experiencing both the generalized anomeric and gauche effects makes the Ishikawa´s reagent an ideal choice to study the governing stereoelectronic interactions of the conformational equilibrium of organofluorine compounds. T

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35

Rivera, Augusto, Jicli José Rojas, John Sadat-Bernal, Jaime Ríos-Motta, and Michael Bolte. "Mechanochemical synthesis and X-ray structural characterization of three 3-nitrophenol cocrystals with three aminal cage azaadamantanes: the role of the stereoelectronic effect on intermolecular hydrogen-bonding patterns." Acta Crystallographica Section C Structural Chemistry 75, no. 12 (2019): 1635–43. http://dx.doi.org/10.1107/s205322961901516x.

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The structures of the cocrystalline adducts of 3-nitrophenol (3-NP) with 1,3,5,7-tetraazatricyclo[3.3.1.13,7]decane [HMTA, (1)] as the 2:1:1 hydrate, 2C6H5NO3·C6H12N4·H2O, (1a), with 1,3,6,8-tetraazatricyclo[4.3.1.13,8]undecane [TATU (2)] as the 2:1 cocrystal, 2C6H5NO3·C7H14N4, (2a), and with 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane [TATD, (3)] as the 2:1 cocrystal, 2C6H5NO3·C8H16N4, (3a), are reported. In the binary crystals (2a) and (3a), the 3-nitrophenol molecules are linked via O—H...N hydrogen bonds into aminal cage azaadamantanes. In (1a), the structure is stabilized by O—H...N and

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36

Zhou, Pan-Pan, Wen-Yuan Qiu, and Neng-Zhi Jin. "Quantification of hyperconjugative effect on the proton donor X–H bond length changes in the red- and blueshifted hydrogen-bonded complexes." Journal of Chemical Physics 137, no. 8 (2012): 084311. http://dx.doi.org/10.1063/1.4748135.

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37

El-Shishtawy, Reda M., Shaaban A. Elroby, Abdullah M. Asiri, and Rifaat H. Hilal. "Pyran-Squaraine as Photosensitizers for Dye-Sensitized Solar Cells: DFT/TDDFT Study of the Electronic Structures and Absorption Properties." International Journal of Photoenergy 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/136893.

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In an effort to provide, assess, and evaluate a theoretical approach which enables designing efficient donor-acceptor dye systems, the electronic structure and optical properties of pyran-squaraine as donor-acceptor dyes used in dye-sensitized solar cells were investigated. Ground state properties have been computed at the B3LYP/6-31+G**level of theory. The long-range corrected density functionals CAM-B3LYP, PBEPBE, PBE1PBE (PBE0), and TPSSH with 6-311++G**were employed to examine absorption properties of the studied dyes. In an extensive comparison between experimental results and ab initio b

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38

Schaefer, Ted, James Peeling та Rudy Sebastian. "Solvent and α-substituent perturbations of the 2H/1H isotope shifts in the 13C nuclear magnetic resonance of toluene-α-d3". Canadian Journal of Chemistry 65, № 3 (1987): 534–37. http://dx.doi.org/10.1139/v87-093.

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The 2H/1H isotope effect on 13C nmr chemical shifts, nΔ, n being the number of intervening bonds between 2H and 13C nuclei, in toluene-α-d3 is solvent dependent. For example, 1Δ ranges from 817 ppb in CD3OH to 869 ppb in acetone-d6 solutions, a positive number indicating increased shielding in the deuterated species. 1Δ is linearly dependent on a function of the refractive index, nD, of the solvent, allowing extrapolation to nD = 1. The hyperconjugative model, in which the C—D bond is a poorer electron donor to the aromatic system than is a C—H bond, is tested for the substituents CH2D, CHD2,

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39

Wrackmeyer, Bernd, and Oleg L. Tok. "Hyperconjugation In Trialkylboranes Shown By Indirect Nuclear Spin-Spin Coupling Constants. Experimental Data And Density Functional Theory (Dft) Calculations." Zeitschrift für Naturforschung B 60, no. 3 (2005): 259–64. http://dx.doi.org/10.1515/znb-2005-0304.

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Trimethylborane (1), triethylborane (2), 1,3-dimethyl-1-boracyclopentane (3), 1-methyl-1- boracyclohexane (4), 9-methyl- and 9-ethyl-9-borabicyclo[3.1.1]nonane [5(Me) and 5(Et)], and 1- boraadamantane (6) were studied by 11B and 13C NMR spectroscopy with respect to coupling constants 1J(13C,11B) and 1J(13C,13C). Results of DFT calculations at the B3LYP/6-311+g(d,p) level of theory show satisfactory agreement with the experimental data. Hyperconjugation arising from C-C σ bonds adjacent to the tricoordinate boron atom is indicated, in particular for 1-boraadamantane (6), by the optimised calcul

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40

Tarika, J. D. Deephlin, C. L. Shiny, X. D. Divya Dexlin, D. Deva Jayanthi, S. Antony, and T. Joselin Beaula. "Probing into the Outcome of Charge Transfer Interactions and Hyperconjugative Effect on the Antibacterial Molecule 4-dimethylaminopyridine using Spectroscopic Elucidations and DFT Calculations." Journal of Molecular Structure 1251 (March 2022): 132059. http://dx.doi.org/10.1016/j.molstruc.2021.132059.

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41

Wayner, Danial D. M., and Donald R. Arnold. "Substituent effects on benzylic radical hydrogen hyperfine coupling constants. Part 4. The effect of branching of the alkyl substituent." Canadian Journal of Chemistry 63, no. 9 (1985): 2378–83. http://dx.doi.org/10.1139/v85-394.

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The effects of substituents in the meta and para positions of the benzyl radical on the α-hydrogen hyperfine coupling constants (hfc's) are discussed. The electron spin resonance (esr) spectra of the para-methyl, ethyl, isopropyl, and tert-butyl substituted benzyl and cumyl radicals are analysed. Hyperconjugation involving the C—C bond is 40–60% as effective as C—H hyperconjugation for delocalizing spin density. This conclusion is supported by INDO molecular orbital calculations. Similar analysis of the 13Cmr spectra of the para-alkyl substituted cumyl carbocations provides evidence that C—C h

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42

Imran, P. K. Mohamed, and K. Subramani. "Theoretical Studies of Some Fluoro Compounds with Silicon, Phosphorus and Sulphur and Establishment of Negative Hyperconjugation through Calculation of Charge." E-Journal of Chemistry 5, no. 1 (2008): 136–43. http://dx.doi.org/10.1155/2008/468284.

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Hyperconjugation is an act to build π bond character into bonds that have only σ character. Negative Hyperconjugation is the flow or movements of electrons from π to σ* orbitals and more particularly from π orbital of a carbon atom to the σ* orbital of the C—X bond, where X is any electronegative atom. This effect is different from Inductive effects. An attempt is made to study the negative hyperconjugation (Anomeric Effect) by the calculation of the charges at the Density Functional Theory (DFT) level for some compounds with hypervalent atoms like Si, P & S

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43

Buffam, D. J., T. S. Sorensen, and S. M. Whitworth. "A study of the observable axial- and equatorial-2,4-dimethyl-2-adamantyl cations. Further examples of equilibrating nonclassical structures in "ordinary" tertiary carbocations." Canadian Journal of Chemistry 68, no. 10 (1990): 1889–93. http://dx.doi.org/10.1139/v90-292.

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The title cations have been prepared insitu from the corresponding tertiary alcohols, using three different superacid systems. The 13C NMR spectra were measured at a number of different temperatures, using the structurally related 13C peaks of internal 2-methyl-2-adamantyl cation as a reference. Using this protocol, one finds that the 13C chemical shifts of the four β carbons are quite temperature dependent, two of them shifting to higher field and the other two on the opposite face shifting to lower field, or vice versa, as the temperature is increased or decreased. This behavior is uniquely

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Koskinen, Mikko, Ilpo Mutikainen, and Hannu Elo. "Crystal and Molecular Structures of Two Isomers of Phenylglyoxal Bis(amidinohydrazone) [‘Phenylglyoxal Bis(guanylhydrazone)’] Sulphate." Zeitschrift für Naturforschung B 51, no. 8 (1996): 1161–72. http://dx.doi.org/10.1515/znb-1996-0817.

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The first crystallographic study on an aromatic analogue of the antileukemic agent methylglyoxal bis(amidinohydrazone) (MGBG) is reported. Thus, the crystal and molecular structures of two different geometrical isomers of phenylglyoxal bis(amidinohydrazone) (PhGBG) sulphate were determined by single-crystal X-ray diffraction. Crystals were prepared by recrystallizing PhGBG sulphate using either water or aqueous ethanol (volume ratio ethanol:water 1:4) as the solvent. Depending on the solvent, different types of crystals were obtained although the PhGBG sulphate employed was in the both cases f

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Francisco, Camila B., Cleverton S. Fernandes, Ulisses Z. de Melo, Roberto Rittner, Gisele F. Gauze, and Ernani A. Basso. "Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines." Beilstein Journal of Organic Chemistry 15 (April 1, 2019): 818–29. http://dx.doi.org/10.3762/bjoc.15.79.

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The presence of strong stereoelectronic interactions involving the substituents in cis-2-substituted cyclohexanes may lead to results different from those expected. In this work, we studied the conformational behavior of cis-2-fluoro- (F), cis-2-chloro- (Cl), cis-2-bromo- (Br) and cis-2-iodocyclohexylamine (I) by dynamic NMR and theoretical calculations. The experimental data pointed to an equilibrium strongly shifted toward the ea conformer (equatorial amine group and axial halogen), with populations greater than 90% for F, Cl and Br in both dichloromethane-d 2 and methanol-d 4. Theoretical c

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MENG, YAN, CHUANJIN TIAN, FENGTING WANG, et al. "HYPERCONJUGATION EFFECT ON THE STRUCTURAL STABILITY OF A TERT-BUTYL AND ITS DERIVED C4Hn(n = 4–10) ISOMERS." Journal of Theoretical and Computational Chemistry 11, no. 06 (2012): 1217–25. http://dx.doi.org/10.1142/s0219633612500812.

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The hyperconjugation effect on molecular structural stability is studied by performing first-principles calculations on the tert-butyl and its derived C 4 H n(n = 4–10) isomer structures. Four of the isomer structures with n = 7–10 were found to show hyperconjugation similar to that in the tert-butyl, with hyperconjugation orbital energies decreasing with the increase of the number of hydrogen atoms participating in the hyperconjugation (PIH). The distribution of charge carried by the PIH hydrogen atoms is uniform, which reveals a delocalization character in the electronic structures; and the

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Zhao, Yu, Jie Zeng, and Jun Zhu. "Tuning the hyperconjugative aromaticity in Au(iii)-substituted indoliums." Dalton Transactions 50, no. 23 (2021): 8096–101. http://dx.doi.org/10.1039/d1dt00599e.

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Sarkar, Subramee, Swaroop Chandra, B. Suryaprasad, N. Ramanathan, K. Sundararajan, and A. Suresh. "Conformational topography of tris(2-methylbutyl) phosphate and the influence of methyl branching at the non-hyperconjugative carbon on the conformational landscape: insights from matrix isolation infrared spectroscopy and DFT computations." Physical Chemistry Chemical Physics 22, no. 42 (2020): 24372–92. http://dx.doi.org/10.1039/d0cp03403g.

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Saltzman, Martin D. "John William Baker and the origin of the Baker-Nathan effect." Bulletin for the History of Chemistry 37, no. 2 (2012): 82–90. https://doi.org/10.70359/bhc2012v037p082.

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This paper will first deal with the life of John William Baker, then examine how Baker and his collaborator, Wilfred Samuel Nathan, discovered what was believed to be the first example of hyperconjugation. Next, it will briefly discuss the downfall of the Baker-Nathan effect as an explanation of what happens in unexpected rate accelerations in reactions in solns. It would seem that the disappearance of the Baker-Nathan effect from chem. literature is due to a combination of doubt over the utility of the concept in its original and rather restricted realm of application (reactivity in soln.) an

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Exner, Otto, and Stanislav Böhm. "Baker–Nathan effect, hyperconjugation and polarizability effects in isolated molecules." Journal of the Chemical Society, Perkin Transactions 2, no. 6 (1997): 1235–40. http://dx.doi.org/10.1039/a605630j.

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