Hydrogen-bonded dimers and the 2.86-.mu. band in alcohols

Hammaker, Robert M.; Clegg, Robert M.; Patterson, L. K.; Rider, Paul E.; Rock, S. L.

doi:10.1021/j100851a090

Cited by 24 publications

(6 citation statements)

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“…For the dilute solutions used in this study, these quantities can be taken as equal to those for cyclohexane. At 25 °C we found 2x2pu/103RT = 7.78 X 10-8 cgs and 6/(pCp) = 3.55 cm3/kcal when the concentrations are expressed in mol/L and the average volume change AV°and enthalpy change AH0 for the formation of one H bond in cm3/mol and kcal/mol, respectively. In this study we have assumed that AV°can be neglected with respect to the enthalpy term in eq 17. Indeed |AV°| is probably less than 3 cm3/mol.34 On the other hand, \AH°\ is larger than 5 kcal/mol.1,2,5•6,21-23 Thus AV°r epresents less than 15% of the enthalpy term and may be neglected when considering the errors resulting from the approximations involved in the derivation of eq 14, 17, 19, and 20 (see below), particularly the assumed absence of species other than A, A", and AnC.…”

Section: Discussionmentioning

confidence: 79%

Ultrasonic absorption in relation to hydrogen bonding in solutions of alcohols. 2. Ultrasonic relaxation spectra of solutions of alcohols in cyclohexane

Djavanbakht¹,

Láng²,

Zana³

1977

J. Phys. Chem.

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The ultrasonic absorption of solutions of ethanol, 1-butanol, 1-octanol, 1-dodecanol, 1-hexadecanol, 3-octanol, 2-methyl-3-heptanol, and 2,4-dimethyl-3-hexanol in cyclohexane at 25 °C has been measured in the frequency range 4-250 MHz. The relaxation spectra of all of the investigated solutions could be fitted to a relaxation equation with a single relaxation frequency. The results have been interpreted on the basis of a reaction mechanism where n alcohol molecules associate to give cyclic and noncyclic n-mers. The absorption is attributed to the perturbation by the sound waves of the association equilibrium leading to noncyclic n-mers. For all primary alcohols no fit to the data could be obtained for = 3 but equally good fits were obtained for = 4 and n-5, except with 1-hexadecanol for which = 5 provides the best fit. The results indicate that (1) the rate of association of alcohol molecules through H bonds is close to its diffusion-controlled limit, even for the most hindered alcohol investigated; (2) the dissociation rate constant of one alcohol molecule from a noncyclic rc-mer is only very slightly dependent on the alcohol chain length for primary alcohols. This rate constant increases with the degree of steric hindrance, reflecting the decreased stability of noncyclic aggregates. For 2methyl-3-heptanol the best fit to the data is obtained for = 3. Likewise, the results for 2,4-dimethyl-3-hexanol appear to indicate that the association of this alcohol is essentially restricted to dimerization. Larger associated species appear to be present only in very small amount. The relation between ultrasonic absorption data and dipole moment data for octanol solutions is examined.

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Section: Discussionmentioning

confidence: 79%

Ultrasonic absorption in relation to hydrogen bonding in solutions of alcohols. 2. Ultrasonic relaxation spectra of solutions of alcohols in cyclohexane

Djavanbakht¹,

Láng²,

Zana³

1977

J. Phys. Chem.

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“…i 4 The following paH values were found in mixtures 3.53 X M in tetrabutylammonium picrate and 0.226, 0.439, and 0.835 M in picric acid: 8.92, 8.51, and 8.10, respectively, from which an average value of K f~p i a -= 2.4 f 0.5 was obtained. Picric acid2 and tetrabutylammonium picrate2 were products used previously.…”

Section: The Homoconjugation Constant Of Picricmentioning

confidence: 79%

Temperature dependence of the molar absorptivity of the OH stretching vibration

Hoover¹,

Robinson²,

McQuate³

et al. 1969

J. Phys. Chem.

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Table I Electrolyte' (in propylene carbonate) t -0 18ec 10 aec 1 min 10 min 1 hr ----.-IBo (mA/am*) at time indiaated-0.257 m LiC104->12 10.2 7 . 8 5.4 2.8 1.6 <0.001 m HzO 0.02 m HzO 0.229 m LiC104->10 8 3.1 1.5 0.30 0.026 0.257 m LiC10,->5 -3 -1 -0.1 .. . .. . 0.54 m HzO time. Values previously r e p~r t e d~~~~~ are consistent with our measurements after 10 min to 1 hr. Our values at t = 0 were obtained by extrapolation on a tl'l scale. I n the dry (<0.001 m HzO) electrolyte, the doublelayer capacity (obtained from the initial portion of the potential-time trace) is approximately 45 pF/cm2, a reasonable value for a rough solid metal surface. In the presence of 0.54 m HzO, the capacity drops to as low as 0.3 pF/cm2, indicating the formation of a dielectric film (possibly LiOH) on the metallic surface. Itis not possible a t this time to distinguish between the effects of recrystallization of the cold-worked surface and the effect of trace water in dry electrolyte, but future experiments with ultradry electrolyte should make this distinction clear.* (7) Propylene carbonate was purified by distillation and analyzed by gas chromatography as described by R. Absorptivity of the OH Stretching VibrationSir: Several have reported the temperature dependence of the molar absorptivity for the fundamental OH stretching vibration of various monomeric molecules in dilute solution; corrections for this temperature dependence have been made by Hammaker, et al.,4 for solutions of methanol, t-butyl alcohol, and di-t-butyl carbinol in carbon tetrachloride. Finch and Lippincott6 have suggested that a true temperature dependence should exist for hydrogen-bonded complexes. Thus, if the solute should hydrogen bond to the solvent, a temperature dependence would be expected. However, Fletcher and Heller6 argue that the molar absorptivity should not change with temperature, and therefore consider any temperature adjust-100 90 80 70 >. h 60 8 9 5 0 5 40 E 30 6 20 1 0 O( e 35'C A 60'C I I I I I I I I I I 0. 1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1. 0 HEAD SPACE (mi) Figure 1. CH stretch of methanol in carbon tetrachloride at 35 and 60' as a function of the head space over the solution. concentration was 0.0048 M at 35".Change in the molar absorptivity for the OH andThe solution ment incorrect. Swenson,' in an attempt to determine the cause of this temperature dependence for methanol in carbon tetrachloride solution, has ascribed the decrease of the molar absorptivity with increasing temperature to reduced concentration of the methanol in solution due to evaporation of the methanol into the head space above the solution. Thus Swenson concludes that a true temperature dependence of the molar absorptivity does not exist. Because of the relative importance of the temperature dependence of the molar absorptivity to the interpretation of spectral data, it seemed that some of our preliminary results in this area should be reported. The change in the molar absorptivity as a function of increasing head space over a solution of methanol in carbon tetrach...

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“…3470 and 3390 cm-', which have been assigned to associated forms of alcohols (6,8,11). These absorptioils are either absent or obscured by the band at 3300 cm-I when salt is present (see Fig.…”

Section: Inpared Us Nuclear Maguetic Resonancementioning

confidence: 97%

“…; Kc = 25. For simplicity we assume that at low concentrations the dimer, in which one of the two OH protons is hydrogen bonded, is the only polymer present (8,9). Consistent with previous studies (7) we assume a typical dimerization constant, K,, of 0.75 M-'.…”

Section: Table I1mentioning

confidence: 99%

Anion–molecule complexes in solution. III. Nuclear magnetic resonance studies of halide ion–alcohol association

Green¹,

Martin²,

Cassie³

et al. 1969

Can. J. Chem.

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Certain alkyl-, aryl-, and arene-substituted alcohols form linear, hydrogen bonded complexes with bromide and other halide ions in tetrachloromethane. The hydroxyl proton shifts ca. 4 p.p.m. downfield in the complex, regardless of the degree or type of substitution. The interaction is enhanced by inductive electron withdrawal by substituents on the C-0-H moiety. A comparison of the present results with infrared spectroscopy shows that the absorption at ca. 3300 cm-I is entirely due to 1 :I alcohol-anion complexes. The a coefficient in Buckingham's equation for electrostatic interaction of a molecule with an ion, 8csE = aE, -bE2, is found to be 5.5 for alcohol 0-H bonds.Canadian Journal of Chemistry, 47, 1639 (1969) Nuclear magnetic resonance (n.m.r.) and infrared (i.r.) spectroscopy have been used extensively in the detection and characterization of the hydrogen bonding of alcohols and other hydroxyl bearing compounds to a variety of bases (1-3). Characteristically, hydrogen bond formation results in a decrease in shielding of the hydrogen nucleus. The extent of this deshielding has been regarded as a measure of hydrogen bond strength, in much the same way as have hydrogen bond shifts and intensities in the i.r. (1,3,4). Both the i.r. frequency shift and the n.m.r. shielding change have been correlated with the enthalpy of hydrogen bond formation (5).Pursuant to our studies of specific complexes to anions in weakly interacting solvents, we have observed deshielding of hydroxyl protons in methanol, pjimary, secondary, and tertiary alcohols, and a phenol, of magnitude up to 4.5 p.p.m., on addition of a tetrabutylammonium salt to a dilute solution of the alcohol in tetrachloromethane. We interpret the monotonic salt concentration dependence of the hydroxyl proton shifts as arising from specific hydrogen bonded interaction of the alcohols with the anions. alcohol to alcohol hydrogen bonding, and the proton shielding observed as a function of the halide ion concentration. Experimental MaterialsMetllartol This was Shawinigan reagent grade, and contained less than 0.2% water when received. This material was dried by storing over 4A molecular sieves (m.s.) for several days; tlie initial vigorous effervescence ceased after about 24 h. The tightly stoppered vial was kept in tlie dry-box. Samples containing nietlianol and tetrabutylammonium bromide decomposed slowly, the n.ni.r. spectrum showing a change after 1 day, but no observable change within 1 11 of sample preparation. All speclra were obtained within 1 11 of preparation of the sample. E t l~a~~o lThis was 98 %, as received, and showed no benzene in the n.m.r. and, at most, traces of water. This niaterial was distilled, and a center fraction totalling ca. 75% collected on n1.s. The fraction collected was refluxed over tlie m.s. for 1 11. The material was then redistilled with a center fraction totalling ca. 50% being collected on m.s. (boiling range 0.4 "C). The tightly-stoppered flask was immediately transferred to the dry-box, where the ethanol was placed in a ...

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Hydrogen-bonded dimers and the 2.86-.mu. band in alcohols

Cited by 24 publications

References 0 publications

Ultrasonic absorption in relation to hydrogen bonding in solutions of alcohols. 2. Ultrasonic relaxation spectra of solutions of alcohols in cyclohexane

Ultrasonic absorption in relation to hydrogen bonding in solutions of alcohols. 2. Ultrasonic relaxation spectra of solutions of alcohols in cyclohexane

Temperature dependence of the molar absorptivity of the OH stretching vibration

Anion–molecule complexes in solution. III. Nuclear magnetic resonance studies of halide ion–alcohol association

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