Pulsed carbon-13 Fourier transform nuclear magnetic resonance spectra of monohalo-substituted cyclohexanes at low temperatures

Subbotin, O. A.; Sergeev, N. M.

doi:10.1021/ja00838a022

Cited by 47 publications

(12 citation statements)

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“…The solid-state 13 C spectra of the TOAB, AT-4, AT-2, and AT-0.5 samples are shown in Figure a. As expected, in the solid state, the signals are shifted to higher chemical shifts due to the predominance of segments with an all-trans conformation, leading to the loss of the γ-gauche shielding effect − (Table ). More importantly, in the 13 C spectrum of AT-4 one can see the emergence of new signals besides the relatively stronger signals of pure TOAB.…”

Section: Resultsmentioning

confidence: 62%

Investigation into the Mechanism and Microstructure of Reaction Intermediates in the Two-Phase Synthesis of Alkanethiol-Capped Silver Nanoparticles

2015

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To gain better control over the characteristics of the alkanethiol-capped silver nanoparticles (SNP) prepared by the two-phase method, the intermediate stage of this reaction and the structure of the precursor compound were investigated. Samples taken from the intermediate stage of the reaction were analyzed by NMR and vibrational spectroscopy both in solution and after solvent removal. The (1)H NMR chemical shifts of the complexes formed during the phase-transfer step were used to detect any structural changes that occur upon introduction of nonanethiol. Moreover, the presence of silver thiolate was monitored by comparing the FTIR and Raman spectra of silver nonanethiolate with the dried samples. Further insights into the microstructure of the intermediate compounds were sought by characterizing samples differing in molar ratios of tetraoctylammonium bromide (TOAB) to silver nitrate (AgNO3). (13)C solid-state NMR chemical shifts, (13)C relaxation times, and the DSC transitions of these samples revealed a dependence of their phase structure on the initial concentration of the reagents. At least two phases with distinct mobility and conformational ordering of their octyl chains were identified in the samples prepared with excess TOAB, which was associated with the presence of multiple anionic species. The observations regarding the composition of the phase-transfer product were further related to the quality of the resulting nanoparticles. It was demonstrated that a large excess of TOAB, which is commonly used in two-phase methods, can be avoided without compromising the size and dispersity of the silver nanoparticles produced. This modification to the synthetic procedure simplifies the purification of the product, mitigates the propensity of the nanoparticles for aggregation, and facilitates their redispersion.

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Section: Resultsmentioning

confidence: 62%

Investigation into the Mechanism and Microstructure of Reaction Intermediates in the Two-Phase Synthesis of Alkanethiol-Capped Silver Nanoparticles

2015

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“…It is well-known that in the liquid phase, the e-conformer is more stable, and that upon cooling the liquid, the e-conformer should be even more preferred. [40,41] Based on previous infrared studies, we conclude that we may have some of the a-conformer in the matrix. Our evidence for this comes from the fact that although most of the parent bands are identical for the a-versus e-conformer, there are a few bands for which the a-conformer's fundamental does not overlap with that of the e-conformer.…”

Section: Discussionmentioning

confidence: 57%

Matrix Isolation Infrared Spectroscopic and Density Functional Theory Study of the 1:1 Complex of Bromocyclohexane with NH₃: Evidence for a Weak C–H–N Hydrogen Bond

Hess

Samet

2008

Spectroscopy Letters

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The hydrogen-bonded bromocyclohexane-ammonia complex has been isolated and characterized for the first time in argon matrices at 16 K. Coordination of the proton adjacent to the Br substituent on the cyclohexane ring to the amino nitrogen was evidenced by distinct blue shifts of bending modes involving the H-C 1 -Br unit. In particular, C-C 1 -Br, H-C 1 -Br, and C-C 1 -H bending modes produced blue shifts ranging from 2.8 to 12.2 cm À1 . Density Functional Theory (DFT) calculations at the B3LYP=6-31 þ G(d, p) level yield an essentially linear Br-C 1 -H-NH 3 hydrogen bond with a C-H-N distance of 2.412 Å and a hydrogen bond energy of 2.95 kcal=mol.

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“… a Experimental error is ±0.5 Hz. b Calculated values were obtained at the SOPPA(CCSD)/EPR-III and DFT/B3LYP/EPR-III levels. DFT-calculated values are shown in parentheses. c Only absolute values of these couplings were measured in this work. d Taken from ref . …”

Section: Resultsmentioning

confidence: 99%

Effect of Electronic Interactions on NMR ¹J_CF and ²J_CF Couplings in cis- and trans-4-t-Butyl-2-fluorocyclohexanones and Their Alcohol Derivatives

et al. 2011

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In order to study the influence of hyperconjugative, inductive, steric, and hydrogen-bond interactions on (1)J(CF) and (2)J(CF) NMR spin-spin coupling constants (SSCCs), they were measured in cis- and trans-4-t-butyl-2-fluorocyclohexanones and their alcohol derivatives. The four isotropic terms of those SSCCs, Fermi contact (FC), spin dipolar (SD), paramagnetic spin-orbit (PSO), and diamagnetic spin-orbit (DSO), were calculated at the SOPPA(CCSD)/EPR-III level. Significant changes in FC and PSO terms along that series of compounds were rationalized in terms of their transmission mechanisms by employing a qualitative analysis of their expressions in terms of the polarization propagator formalism. The PSO term is found to be sensitive to proximate interactions like steric compression and hydrogen bonding; we describe how it could be used to gauge such interactions. The FC term of (2)J(CF) SSCC in cis-4-t-butyl-2-fluorocyclohexanone is rationalized as transmitted in part by the superposition of the F and O electronic clouds.

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Pulsed carbon-13 Fourier transform nuclear magnetic resonance spectra of monohalo-substituted cyclohexanes at low temperatures

Cited by 47 publications

References 1 publication

Investigation into the Mechanism and Microstructure of Reaction Intermediates in the Two-Phase Synthesis of Alkanethiol-Capped Silver Nanoparticles

Investigation into the Mechanism and Microstructure of Reaction Intermediates in the Two-Phase Synthesis of Alkanethiol-Capped Silver Nanoparticles

Matrix Isolation Infrared Spectroscopic and Density Functional Theory Study of the 1:1 Complex of Bromocyclohexane with NH₃: Evidence for a Weak C–H–N Hydrogen Bond

Effect of Electronic Interactions on NMR ¹J_CF and ²J_CF Couplings in cis- and trans-4-t-Butyl-2-fluorocyclohexanones and Their Alcohol Derivatives

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Pulsed carbon-13 Fourier transform nuclear magnetic resonance spectra of monohalo-substituted cyclohexanes at low temperatures

Cited by 47 publications

References 1 publication

Investigation into the Mechanism and Microstructure of Reaction Intermediates in the Two-Phase Synthesis of Alkanethiol-Capped Silver Nanoparticles

Investigation into the Mechanism and Microstructure of Reaction Intermediates in the Two-Phase Synthesis of Alkanethiol-Capped Silver Nanoparticles

Matrix Isolation Infrared Spectroscopic and Density Functional Theory Study of the 1:1 Complex of Bromocyclohexane with NH3: Evidence for a Weak C–H–N Hydrogen Bond

Effect of Electronic Interactions on NMR 1JCF and 2JCF Couplings in cis- and trans-4-t-Butyl-2-fluorocyclohexanones and Their Alcohol Derivatives

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Matrix Isolation Infrared Spectroscopic and Density Functional Theory Study of the 1:1 Complex of Bromocyclohexane with NH₃: Evidence for a Weak C–H–N Hydrogen Bond

Effect of Electronic Interactions on NMR ¹J_CF and ²J_CF Couplings in cis- and trans-4-t-Butyl-2-fluorocyclohexanones and Their Alcohol Derivatives