Solvent and concentration dependence of the hydroxyl chemical shift of methanol

Wendt, Mark A.; Meiler, John G.; Weinhold, Frank; Farrar, Thomas C.

doi:10.1080/00268979809482198

Cited by 60 publications

(40 citation statements)

References 9 publications

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“…At room temperature, the J-coupling for the OH and methyl resonances are well resolved up to a concentration of about 2.0 mole percent methanol in benzene. For methanol in dimethyl sulfoxide the fine structure is well resolved up to concentrations of about 15.0 mole percent methanol 8 .…”

Section: Resultsmentioning

confidence: 87%

Oxygen-17-induced proton relaxation rates for alcohols and alcohol solutions

Farrar

Wendt

Zeidler

1999

J. Braz. Chem. Soc.

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O uso de amostras de álcoois enriquecidas com 17 O, para medir o tempo de correlação do vetor internuclear OH funciona bem quando o próton da hidroxila sofre uma troca rápida. Para álcoois tais como metanol e etanol, a taxa de troca da hidroxila para amostras puras é relativamente lenta, mesmo à temperatura ambiente, podendo resultar em erros sistemáticos significativos se efeitos de troca lenta não forem considerados. Para trocas lentas do próton da hidroxila, 17 OH, o sinal é uma função relativamente complexa da razão de troca química do próton da hidroxila, do acoplamento de spin OH (cerca de 80 Hz para álcoois e água) e do tempo de relaxação para o oxigênio. A largura de linha do OH pode tornar-se tão grande, devido à relaxação escalar com o núcleo de oxigênio, que o sinal torna-se muito difícil de detectar. Para etanol puro enriquecido com 17 O, à temperatura ambiente, o tempo de relaxação do oxigênio é de aproximadamente 3,0 ms e a largura de linha do próton da hidroxila é maior do que 1000 Hz.The use of 17 O enriched samples of alcohols to measure the correlation time of the OH internuclear vector works well when the hydroxyl proton exchanges rapidly. For alcohols such as methanol and ethanol the hydroxyl exchange rate for neat samples is relatively slow even at room temperature and significant systematic errors result if slow exchange effects are not considered. For slow exchange the hydroxyl proton, 17 OH, signal is a relatively complex function of the chemical exchange rate of the hydroxyl proton, the OH spin coupling (about 80 Hz for alcohols and water) and the relaxation time for the oxygen. The OH linewidth can become so large due to scalar relaxation with the rapidly relaxing oxygen nucleus that the signal becomes very difficult to detect. For neat 17 O enriched ethanol at room temperature the oxygen relaxation time is about 3.0 ms and the hydroxyl proton linewidth is over 1000 Hz.

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Section: Resultsmentioning

confidence: 87%

Oxygen-17-induced proton relaxation rates for alcohols and alcohol solutions

Farrar

Wendt

Zeidler

1999

J. Braz. Chem. Soc.

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“…DMSO may be bound to one or two alcohol molecules depending on the concentration [12 ± 15]. In dilute solutions, the 1 : 1 complex 1 between MeOH and DMSO is clearly favoured over the 2 : 1 complex 2 [12], in keeping with the semiempirically calculated 8.28 and 7 kcal/mol binding energy for the H-bonds in 1 and 2, respectively [12] (Fig. 1).…”

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confidence: 76%

“…3) (14) and HOÀC(12) of 15 reveals that HOÀC (14) resonating at 3.64 ppm is involved in a strong H-bond and HOÀC (12), resonating at 2.23 ppm ± at best ± in a weak one. The strong downfield shift of HOÀC (14) is clearly due to the bifurcated Hbond to the 9,11-epoxy substituent and to HOÀC (12), and this intramolecular H-bond is responsible for the synperiplanar arrangement of HÀOÀC (12)ÀH. These data are compatible only with structure 15a.…”

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confidence: 96%

1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

Bernet

Vasella

2000

HCA

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The interpretation of 1H‐NMR chemical shifts, coupling constants, and coefficients of temperature dependence (δ(OH), J(H,OH), and Δδ(OH)/ΔT values) evidences that, in (D6)DMSO solution, the signal of an OH group involved as donor in an intramolecular H‐bond to a hydroxy or alkoxy group is shifted upfield, whereas the signal of an OH group acting as acceptor of an intramolecular H‐bond and as donor in an intermolecular H‐bond to (D6)DMSO is shifted downfield. The relative strength of the intramolecular H‐bond depends on co‐operativity and on the acidity of OH groups. The acidity of OH groups is enhanced when they are in an antiparallel orientation to a C−O bond. A comparison of the 1H‐NMR spectra of alcohols in CDCl3 and (D6)DMSO allows discrimination between weak and strong intramolecular H‐bonds. Consideration of IR spectra (CHCl3 or CH2Cl2) shows that the rule according to which the downfield shift of δ(OH) for H‐bonded alcohols in CDCl3 parallels the strength of the H‐bond is valid only for alcohols forming strong intramolecular H‐bonds. The combined analysis of J(H,OH) and δ(OH) values is illustrated by the interpretation of the spectra of the epoxyalcohols 14 and 15 (Fig. 3). H‐Bonding of hexopyranoses, hexulopyranoses, alkyl hexopyranosides, alkyl 4,6‐O‐benzylidenehexopyranosides, levoglucosans, and inositols in (D6)DMSO was investigated. Fully solvated non‐anomeric equatorial OH groups lacking a vicinal axial OR group (R=H or alkyl, or (alkoxy)alkyl) show characteristic J(H,OH) values of 4.5 – 5.5 Hz and fully solvated non‐anomeric axial OH groups lacking an axial OR group in β‐position are characterized by J(H,OH) values of 4.2 – 4.4 Hz (Figs. 4 – 6). Non‐anomeric equatorial OH groups vicinal to an axial OR group are involved in a partial intramolecular H‐bond (J(H,OH)=5.4 – 7.4 Hz), whereas non‐anomeric equatorial OH groups vicinal to two axial OR form partial bifurcated H‐bonds (J(H,OH)=5.8 – 9.5 Hz). Non‐anomeric axial OH groups form partial intramolecular H‐bonds to a cis‐1.3‐diaxial alkoxy group (as in 29 and 41: J(H,OH)=4.8 – 5.0 Hz). The persistence of such a H‐bond is enhanced when there is an additional H‐bond acceptor, such as the ring O‐atom (43 – 47: J(H,OH)=5.6 – 7.6 Hz; 32 and 33: 10.5 – 11.3 Hz). The (partial) intramolecular H‐bonds lead to an upfield shift (relative to the signal of a fully solvated OH in a similar surrounding) for the signal of the H‐donor. The shift may also be related to the signal of the fully solvated, equatorial HO−C(2), HO−C(3), and HO−C(4) of β‐D‐glucopyranose (16: 4.81 ppm) by using the following increments: −0.3 ppm for an axial OH group, 0.2 – 0.25 ppm for replacing a vicinal OH by an OR group, ca. 0.1 ppm for replacing another OH by an OR group, 0.2 ppm for an antiperiplanar C−O bond, −0.3 ppm if a vicinal OH group is (partially) H‐bonded to another OR group, and −0.4 to −0.6 for both OH groups of a vicinal diol moiety involved in (partial) divergent H‐bonds. Flip‐flop H‐bonds are observed between the diaxial HO−C(2) and HO−C(4) of the inositol 40 (J(H...

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“…Despite the fact that the aromatic ring provides a pi electron Lewis-base source of hydrogen bonding, it has been demonstrated that solute-solute aggregation is favored over solute-solvent interactions. It is generally assumed that a marked downfield shift of hydroxylic proton can be attributed to hydrogen bonding [18], the stronger the hydrogen bond, the larger the shift in frequency [19].…”

Section: H-nmr Concentration Dependencementioning

confidence: 99%

Synthesis and Determination of Polymerization Rate Constants of Glucose-Based Monomers

Sharma

Durand

Pucci

2011

Designed Monomers and Polymers

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To prepare non-ionic amphiphilic polymers usable for solubilizing integral membrane proteins, hydrophilic and amphiphilic β-D-glucose-based tris(hydroxymethyl)acrylamidomethane monomers were synthesized and their radical homopolymerization rate constants (f k 2 p /k t ) were determined. The polymerization kinetics, monitored by 1 H-NMR, were carried out in THF in the presence of AIBN as radical initiator. The plot of monomer conversion as a function of time followed Tobolsky's equation. The number of hydroxyl groups, as well as the nature of the substituents grafted onto the hydroxyl groups, was found to alter the rates of polymerization. While the steric hindrance significantly affected the kinetics, intermolecular hydrogen bonds between hydroxyl groups, as demonstrated by NMR investigations at different concentrations and temperatures, may also play a role in the rate constants of polymerization.

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Solvent and concentration dependence of the hydroxyl chemical shift of methanol

Cited by 60 publications

References 9 publications

Oxygen-17-induced proton relaxation rates for alcohols and alcohol solutions

Oxygen-17-induced proton relaxation rates for alcohols and alcohol solutions

1H-NMR Analysis of Intra- and Intermolecular H-Bonds of Alcohols in DMSO: Chemical Shift of Hydroxy Groups and Aspects of Conformational Analysis of Selected Monosaccharides, Inositols, and Ginkgolides

Synthesis and Determination of Polymerization Rate Constants of Glucose-Based Monomers

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