10310
J. Phys. Chem. 1996, 100, 10310-10315
17O-
and 1H-NMR Studies of the Water Structure in Binary Aqueous Mixtures of Halogenated Organic Compounds Kazuko Mizuno,* Kazuya Oda, and Yohji Shindo Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Fukui UniVersity, Fukui 910, Japan
Akiko Okumura Department of Chemistry, Faculty of Science, Nara Women’s UniVersity, Nara 630, Japan ReceiVed: January 26, 1996; In Final Form: April 9, 1996X
The chemical shifts of water (17O- and 1H-NMR) and the spin-lattice relaxation time of water (17O-NMR) were measured on binary aqueous mixtures of halogenated ethanols, propanols, acetamide and acetone to investigate the effect of their halogen groups on water structure. The solute molecules were 2-chloroethanol, 2-bromoethanol, 2-iodoethanol, 2,2-dichloroethanol, 3-chloropropan-1-ol, 2,3-dichloropropan-1-ol, chloroacetamide, and chloroacetone together with ethanol, propan-1-ol, acetamide and acetone. The results give clear evidence of the fact that the hydrogen bonds of the water molecules become weaker around the halogen group irrespective of the presence of an OH group in the molecules.
Introduction Experimental and theoretical studies have been carried out so far on the water structure in aqueous solutions of nonelectrolytes such as alkanols1-5 and halogenoanions.6-8 However, the effects of halogenated nonelectrolytes on water structure have been left to be studied. This is due to their relatively poor solubilities into water. Halogenoalcohols such as 2-chloroethanol (ClEtOH), 2-bromoethanol (BrEtOH), and 3-chloropropan-1-ol (ClPrOH) are, however, miscible with water over a wide range of their concentrations so that their effects on water structure can be studied. It is reasonable to consider that a structural change in water on hydration of solute molecules is related to the change in hydrogen-bonding strength of the water molecules surrounding solute molecules. 1H-NMR is one of the useful methods to study the hydrogen bonds of water molecules in aqueous solutions of nonelectrolytes as well as electrolytes.9,10 This is because the chemical shift of water 1H resonance gives information about the electronic polarization and hydrogenbonding strength of water molecules. In a previous work,11 we carried out 1H-NMR measurements of aqueous halogenoalcohol mixtures using an external reference method and evaluated the chemical shift of the water 1H from that of the water and alcoholic OH proton peak coalesced by their exchange. The results show the high-field shift of the water 1H resonance peak with increasing the alcohol concentrations. We interpret this high-field shift as indicating the breakdown of water structure due to the interaction of the water molecules with the halogen group in the halogenoalcohols. To confirm our interpretation, we have measured FT-IR spectra and 17O-NMR relaxation time of aqueous halogenoalcohol mixtures. In FT-IR study of aqueous ethanol mixtures, it was found that the bending vibration spectra of the water molecules provide significant information about their hydrogen bonds since the bending band does not overlap any band of the alcohol.12 The stretching vibration spectra are not useful for studying aqueous alcohol mixtures because of the overlap with those of the alcohols. The results of the FT-IR studies on the X
Abstract published in AdVance ACS Abstracts, May 15, 1996.
S0022-3654(96)00194-3 CCC: $12.00
aqueous halogenoalcohol mixtures will be reported elsewhere.13 also has an advantage over 1H-NMR in the analysis of the chemical shift of the water in the mixtures, because there is no exchange of water oxygen with the halogenoalcohols. Fister and Herz14 reported the low-field shift of the 17O resonance peak of pure water on cooling and attributed the shift to the deshielding of oxygen nuclei owing to an increase in hydrogen-bonding interaction among water molecules. In aqueous methanol mixtures, the water 17O resonance14,15 and the water 1H resonance peaks16,17 were observed to shift downward with increasing methanol content, and the shifts were interpreted in terms of an increasing hydrogen-bonding interaction among water molecules. Thus, the water 17O peak shifts in the same direction as the water 1H peak. Accordingly, it is reasonable to expect a high-field shift of the water 17O peak in aqueous halogenoalcohol mixtures where the water 1H peak was found to shift to high-field with increasing alcohol contents.11 The 17O nucleus possesses an electric quadrupole moment which interacts with electric field gradient produced by the surrounding electric charges within a molecule containing an 17O nucleus. The electric quadrupolar interaction is the predominant relaxation mechanism for the 17O nucleus. Thus, the spin-lattice relaxation time, T1, of water 17O provides information about the local motion of the water molecules surrounding solute molecules.10,14,18-20 T1 of water 17O has been measured in aqueous mixtures of many kinds of electrolytes and nonelectrolytes but not of halogenoalcohols. We have carried out 17O- and 1H-NMR measurements on aqueous mixtures of several organic halogenated compounds. In the present paper we report the chemical shift and the T1 of the water 17O in aqueous mixtures of halogenated ethanols and propanols. The 1H chemical shift of water is also reported for aqueous mixtures of chloroacetamide and chloroacetone that have no protons exchangeable with water protons. 17O-NMR
Experimental Section Materials. ClEtOH and ClPrOH were purchased from Wako Pure Chemical, BrEtOH, chloroacetone (ClAC), and 2,3dichloropropan-1-ol (DClPrOH) from Tokyo Kasei Organic Chemicals, and 2,2-dichloroethanol (DClEtOH) from Aldrich. © 1996 American Chemical Society
17O-
and 1H-NMR Studies of Water Structure
Figure 1. Chemical shift of the water ClPrOH vs mole fraction of ClPrOH.
17O
J. Phys. Chem., Vol. 100, No. 24, 1996 10311
in aqueous mixtures of
Ethanol (EtOH), propan-1-ol (PrOH), the halogenoalcohols, and ClAC were preserved together with 3 Å molecular sieves and distilled in vacuo. Acetamide (AA) and chloroacetamide (ClAA) of Wako Pure Chemical were recrystallized three times from a mixture of ethyl acetate and diethyl ether (3:1 in volume). Acetone (AC) (Wako Pure Chemical, spectral grade) was used as received. Water was purified twice by repeating distillation of deionized water. The compositions of the mixtures were determined by weight and are denoted by the mole fraction of the halogenated compounds. NMR Measurements. 17O-NMR measurements were carried out with a JEOL GX-270 spectrometer operating at 36.6 MHz. The chemical shift is referenced to the 17O resonance peak of the external CD3OD. A sealed capillary tube of CD3OD, a locking substance, was inserted at the center of a 10 mm sample tube. The chemical shifts of the water 17O in aqueous mixtures of ClPrOH were determined at 25 °C with increasing the mole fraction of ClPrOH up to 0.50. In all the mixtures, only a single peak was observed. The resonance peaks for 17O of the pure halogenoalcohols and of pure water appear at almost the same frequencies,11 but the peaks of the former are much broader than that of the latter. The height of the ClPrOH 17O peak is too low to affect the frequency of the water 17O peak. The spin-lattice relaxation time, T1, was measured for the aqueous mixtures of halogenoalcohols or the amides by inversion-recovery-method. In all the mixtures also, only a single peak was observed for water 17O, and the baseline of the single peak is discriminated from any other peaks for the alcohol and the amide 17O. The concentrations of the solutes were so low and the width of the alcohol 17O peaks so wide that the observed peak is assigned unambiguously to the water 17O in the mixtures. 1H-NMR spectra were measured at 20°C with a JEOL GX270 spectrometer operating at 270 MHz for the aqueous mixtures of AC, AA, ClAC, or ClAA. The chemical shifts are referenced to the peak of the methyl 1H of external sodium 3-(trimethylsilyl)propanesulfonate dissolved in D2O as a locking solvent.11 Results Chemical Shift of the Water 17O in Aqueous ClPrOH Mixtures. Figure 1 shows the concentration dependence of the chemical shift of the water 17O in the aqueous mixtures of ClPrOH. The resonance peak of the water 17O shifts to highfield monotonically with increasing ClPrOH content. The highfield shift of the water 17O peak can be attributed to the shielding of the oxygen nuclei,14,15 or to a decrease in electronic
Figure 2. Chemical shift of the water 1H in aqueous mixtures of AC, AA, ClAC, or ClAA vs mole fraction of solute.
polarization of the water molecules. This result indicates that the hydrogen bonds among the water molecules in the mixtures become weaker with increasing ClPrOH concentration, which is consistent with the conclusion obtained from the 1H-NMR measurements.11 1H Chemical Shift of the Water in Aqueous Mixtures of Ketone or Amide. In Figure 2, the 1H chemical shift of the water in the aqueous mixtures of AA, AC, ClAA, or ClAC is plotted against the concentration. For the mixtures of AA or AC, the resonance peak of the water 1H shifts to low-field with increasing AA or AC concentration. This indicates an increase in the electronic polarization or the hydrogen-bonding strength of the water molecules in the mixtures. The water 1H resonance peak for aqueous mixtures of ClAA or ClAC, on the other hand, shifts to high-field with increasing ClAA or ClAC content, which is ascribed to a decrease in the hydrogen-bonding strength of the water molecules in the mixtures. From the fact that the two solute molecules with the same polar groups (AC and ClAC with a carbonyl group, and AA and ClAA with an amide group) induce the opposite changes in the hydrogen-bonding strength of the water molecules, the changes are ascribed predominantly to the hydration of the part in the solute molecules other than the polar groups; the formation of water structure is due to the hydration of the methyl groups of AC and AA, and the breakdown of water structure is due to the hydration of the chlorine groups of ClAC and ClAA. From Figure 2, the magnitude of the low-field shift for the mixtures of AC with two methyl groups is found to be about twice as large as that for the mixtures of AA with a methyl group. The magnitude of the low-field shifts for these mixtures is approximately proportional to the number of the methyl groups in AC and AA. This result also shows that the observed low-field shifts are interpreted in terms of the formation of water structure around the methyl groups, that is, the hydrophobic hydration. What should be noted in Figure 2 is that the difference in the chemical shift between aqueous AC and aqueous ClAC mixtures is almost equal to that between aqueous AA and aqueous ClAA mixtures. We see that a chlorine substitution of a methyl hydrogen in AC and AA gives rise to almost the same amount of high-field shift of the water 1H peak irrespective of the kind of their polar groups. It is clear that the high-field shifts due to the hydration of the Cl group overwhelm the low-
10312 J. Phys. Chem., Vol. 100, No. 24, 1996
Mizuno et al.
field shifts due to the hydration of the CH3 groups. We discuss this problem later again in the Discussion Section. Here, we should mention the method of determining the chemical shift of water 1H that we employed. The chemical shifts are referenced to the external reference. The low-field shift of the water 1H peak for the aqueous AC mixtures corresponds well to the low-field shift of the water 17O peak in the same mixtures measured using the external reference method.15 Wen-Yang and Herz21 reported a completely different concentration dependence of the chemical shift of the water 1H peak for aqueous mixtures of AC from that shown in Figure 2. The water 1H peak does not shift up to X ) 0.02 and then shifts to high-field with further increase in AC concentration. They referenced the chemical shift of the water 1H to the frequency of the methyl 1H resonance peak of AC, assuming its relatively small shift.21 However, we found that the peak of the methyl 1H also shifts downward almost the same as the peak of the water 1H. This observation corresponds well to their result. Thus, the internal reference method gives no reliable chemical shift of the water 1H in the mixtures. For aqueous ethanol mixtures, we measured both the chemical shift of the water 1H using the external reference method and the frequency of the bending vibrational band of the water molecules.12 The concentration dependence of the chemical shift of the water 1H thus obtained is extremely different from that obtained by the internal reference method, but the concentration dependencies of the hydrogen-bonding strength for the water molecules determined from the 1H-NMR and the IR studies are almost equal. This result indicates that the external reference method is essential to determining the chemical shift of water 1H in aqueous mixtures. T1 of the Water 17O in Aqueous Mixtures of Amide or Halogenoalcohol. The linear relationship between the relaxation rate, R1 ) 1/T1, of water 17O and the solute molarity, m, has been found in a low concentration range of solute (m < 2 mol kg-1) as
R1/R1° ) T1°/T1 ) 1 + Bm
(1)
where T1° and R1° are the relaxation time and the rate of pure water 17O, respectively, and B is a coefficient characteristic of a solute molecule.14,19,20,22,23 For aqueous mixtures of alcohols,14,19,22 amides,19,22 and other organic compounds,22,23 B coefficients are found to be positive, whereas Fister and Hertz reported negative B coefficients for Cl-1, Br-1, and I-1 ions.14 The positive and the negative B coefficients are interpreted as indicating the suppression of the rotational motion of the water molecules around the solute molecules, i.e. the formation of water structure, and inversely the breakdown of water structure, respectively.14 T1 was measured for aqueous mixtures of AA, ClAA, EtOH, ClEtOH, DClEtOH, PrOH, ClPrOH, or DClPrOH at 25 °C. Figure 3 shows the plots of T1°/T1 against m for the mixtures. In Figure 4, B coefficients of the chlorinated acetamides, ethanols, and 1-propanols are plotted as functions of the chlorine number, N, in homologs like AA and ClAA. It is clear that the chlorine substitution of a methyl hydrogen in AA, EtOH, and PrOH gives rise to a decrease in their B coefficients although B remains positive. The T1 of water 17O varies with temperature according to an Arrhenius relation,
T1 ) A exp(-Ea/RT)
(2)
where A is a constant, and Ea is the activation energy of the rotational motion. Ea for aqueous mixtures of the halogenated
Figure 3. T1°/T1 of water 17O vs molality; aqueous mixtures of (a) 1-propanols, (b) ethanols, and (c) acetamides.
Figure 4. B coefficient vs number of chlorine atoms, N, in the chlorinated acetamides, ethanols, or 1-propanols.
compounds should also provide information about the effect of the halogen groups on the water structure. The T1 of water 17O was measured for the 2 mol % (m ) 1.13) aqueous mixtures of EtOH, ClEtOH, DClEtOH, BrEtOH, or IEtOH in the temperature range of 15-35 °C. The Arrhenius plots are shown in Figure 5. The obtained Ea is listed in Table
17O-
and 1H-NMR Studies of Water Structure
J. Phys. Chem., Vol. 100, No. 24, 1996 10313
Figure 6. ∆R1/m vs N for aqueous mixtures of chlorinated acetamides, ethanols, or 1-propanols.
Figure 5. Arrhenius plots of T1 for pure water and 2 mol% aqueous mixtures of EtOH, ClEtOH, DClEtOH, BrEtOH, or IEtOH.
TABLE 1: Ea and ∆Ea Obtained from the Arrhenius Plots for 2 Mol % Aqueous Mixtures of Halogenoethanols alcohol
Ea (kJ mol-1)
∆Ea (kJ mol-1)
(water) EtOH ClEtOH DClEtOH BrEtOH IEtOH
19.1 ( 0.1 22.1 ( 0.1 22.1 ( 0.3 21.2 ( 0.3 21.3 ( 0.1 20.8 ( 0.3
3.0 ( 0.2 3.0 ( 0.4 2.1 ( 0.4 2.2 ( 0.2 1.7 ( 0.4
1. For aqueous ClEtOH mixtures, Ea is close to that for aqueous EtOH mixtures, whereas aqueous DClEtOH mixtures have smaller Ea than do aqueous EtOH mixtures. It is inevitable that activation energies obtained on the basis of the relaxation times measured at several temperatures have a larger uncertainty than the relaxation times themselves, but Table 1 shows that Ea becomes smaller with increasing the size of halogen group from Cl to Br and I. In Figure 4, we find that chlorination of AA, EtOH, and PrOH results in a decrease in their B coefficients by almost the same amount. This leads us to an hypothesis that the decrease in B is associated with the breakdown of the water structure around the chlorine groups, whereas the water structure around the remaining part of the solute molecules remains rather unchanged even after chlorination. In order to verify the above hypothesis, we analyzed the results of the T1 measurement on the basis of the following hydration model: (1) The solute molecules are halogenated organic compounds with N halogen atoms per molecule, and the hydration occurs in two shells with different water structure, one around the halogen group and the other around the remaining part. (2) NMx and Mr moles of water solvate the halogen and the remaining parts of one mole of the solute, respectively. Mx and Mr are constants characteristic of the halogen group and the molecular structure of the remaining part, respectively, at a low concentration of solute like m < 2. R1 in eq 1 is an average over all species of water 17O with different relaxation rates in the mixtures. On the basis of the above hydration model, there are three kinds of water 17O, i.e. the water 17O in the bulk, in the hydration shells around the
halogen group, and around the remaining part of the solute molecules, and their relaxation rates are expressed by R1°, R1x and R1r, respectively. R1° may be assumed to be identical to the relaxation rate of pure water 17O as long as m is small. Since a mixture at the concentration of molality m is composed of m moles of solute and 1000 g (55.5 mol) of water, the R1 of this aqueous mixture may be expressed as
R1 ) (55.5 - mNMx - mMr)R1°/55.5 + mNMxR1x/55.5 + mMrR1r/55.5 ) {(55.5 - mNMx - mMr)R1° + mNMxR1x + mMrR1r}/55.5 ) (1 - mNfx - mfr)R1° + mNfxR1x + mfrR1r
(3)
where fx ) Mx/55.5 and fr ) Mr/55.5. Rearrangement of eq 3 using the relations ∆R1 ) R1 - R°, ∆R1x ) R1x - R1°, and ∆R1r ) R1r - R1° led us to the following equation:
∆R1/m) Nfx∆R1x + fr∆R1r
(4)
In Figure 6, ∆R1/m is plotted against N according to eq 4 for the aqueous mixtures of chlorinated ethanols, 1-propanols, or acetamides. Approximately linear dependences of ∆R1/m on N are obtained. From this result, we may approximate fr∆R1r in eq 4 closely to ∆R1/m obtained for corresponding nonhalogenated homologs. This means that the water structure around the solute molecules other than the halogen group remains almost unchanged from that before chlorination. From the negative slopes of the lines, ∆R1x in eq 4 for the three homologs are found to be negative. Since ∆R1x ) R1x - R1°, this fact shows clearly that a breakdown of water structure occurs in the hydration shell of the halogen groups. In conclusion, the present T1 study shows clearly that the breakdown of water structure occurs around the very halogen groups in the halogenated compounds and verifies the conclusion of the chemical shift study of 1H-NMR described in the above section and in the previous paper.11 Discussion The B coefficients for all the solutes are found to be positive so that all of them are classified as makers of water structure
10314 J. Phys. Chem., Vol. 100, No. 24, 1996
Mizuno et al.
Figure 7. ∆δ/m vs N for aqueous mixtures of chlorinated acetamides, acetones, ethanols, or 1-propanols.
TABLE 2: fx∆R1x, fr∆R1r, fx∆δx, and fr∆δr Obtained from Figures 6 and 7, and |fx∆R1x/fr∆R1r| and |fx∆δx/fr∆δr| solute
fx∆R1x
fr∆R1r
|fx∆R1x/ fr∆R1r|
fx∆δx
fr∆δr
|fx∆δx/ fr∆δr|
acetamides ethanols 1-propanols
-4.5 -3.3 -6.4
18 31 36
0.25 0.11 0.18
-0.087 -0.060 -0.047
0.0089 0.060 0.026
9.8 1.0 1.8
according to the criterion mentioned above. This is contrary to the conclusion obtained from the high-field shift of the water 1H resonance peak for the same mixtures. We will show below that the concentration dependences of the chemical shift of water 1H and the B coefficient are different from each other for the same aqueous mixtures of the halogenated organic compounds. A relationship similar to that expressed by eq 4 should hold also for the chemical shift of the water 1H in terms of ∆δ ) δ - δ°, ∆δx ) δx - δ°, and ∆δr ) δr - δ° and may be expressed again as
∆δ/m ) Nfx∆δx + fr∆δr
(5)
where δ°, δx, and δr are the chemical shifts of the water 1H in the bulk water, in the hydration shells around the halogen group, and around the remaining part, respectively. In Figure 7, ∆δ/m is plotted against N for the aqueous mixtures of chlorinated ethanols, 1-propanols, acetamides, and acetones. The measured ∆δ are positive for the aqueous EtOH12 and aqueous 1-propanol mixtures. For aqueous 1-propanol mixtures, details will be published in a separate paper. ∆δ are positive for the aqueous AA and aqueous AC mixtures also as shown in Figure 2. For the aqueous mixtures of haloethanols,11 chloropropanols,11 ClAA or ClAC, on the other hand, ∆δ is negative in contrast to the cases of ∆R1 and ∆Ea. From eqs 4 and 5, the signs of ∆R1 and ∆δ are positive when |Nfx∆R1x/fr∆R1r| < 1 and |Nfx∆δx/fr∆δr| < 1, and are negative when |Nfx∆R1x/fr∆R1r| > 1 and |Nfx∆δx/ fr∆δr| > 1. fx∆R1x and fx∆δx are correlated to the slopes of the lines in Figures 6 and 7, and fr∆R1r and fr∆δr are also correlated approximately to the intercepts of the lines, as discussed above. |fx∆R1x/fr∆R1r| and |fx∆δx/fr∆δr| thus obtained from the lines are summarized in Table 2 and have the following relationship
|fx∆R1x/fr∆R1r| < 1 < |fx∆δx/fr∆δr|
(6)
The apparent inconsistency of the sign between ∆R1 and ∆δ for the aqueous mixtures of ClAA or halogenated alcohols is attributable to the relationship expressed by eq 6.
The chemical shift of water 1H is directly correlated to the electron density around the water proton, hence to the electronic polarization of water molecules. The changes in the chemical shift of water 1H on dissolving solute molecules directly reflect the intermolecular interaction between solute and water molecules as well as the interaction among water molecules. The quadrupolar relaxation rate of water 17O is, on the other hand, purely intramolecular10 and reflects only local rotational motion of water molecules. The difference in the mechanism of the chemical shift and the relaxation rate spoils the one-to-one correspondence between these two quantities. The deduced relationship of eq 6 is probably due to a small magnitude of |∆R1x/∆R1r|, which implies that the rotational motion of the water molecules is strongly suppressed around the part other than the halogen group in the solute molecules. The halogenoalcohols have much higher proton donating acidity than the corresponding alkanols because of the electron withdrawal by the electronegative halogen groups.24,25 This strong acidity of the OH group in the halogenoalcohols may give rise to the change in the water structure. The almost similar slopes of the lines in Figure 7 shows that the chlorination of a methyl hydrogen causes a decrease in ∆δ/m by almost the same amount irrespective of the kind of solute molecules as exemplified by AA and AC shown in Figure 2. This result shows also that the chlorination of a methyl hydrogen does not cause significant change in the effect of the polar group of the solute molecules on the water structure. The halogen part and the remaining part contribute to the breakdown and to the formation of water structure separately. This is exactly the same conclusion as that of the previous paper.11 Conclusion In aqueous mixtures of ClPrOH, the resonance peak of the water 17O shifts to high-field. The water 1H peak in the aqueous mixtures of AA or AC shifts to low-field, whereas the peak in the mixtures of ClAA or ClAC shifts to high-field. These results show the breakdown of the water structure around the halogen group in the solute molecules, which is the conclusion obtained in the previous paper.11 The study of the T1 of water 17O in the mixtures of halogenated acetamides, ethanols, or 1-propanols also shows that the breakdown is attributable to the interaction of the water molecules with the halogen group in the solute molecules. References and Notes (1) Patterson, D. J. Solution Chem. 1994, 23, 105. (2) Lyashchenko, A. K. In Relaxation Phenomena in Condensed Matter; Coffey, W., Ed.; John Wiley & Sons, Inc.: New York, 1994; p 379. (3) Bergmann, D. L.; Eckert, C. A. ACS Symp. Ser. 1992, 509, 218. (4) Kaatze, U.; Potel, R. J. Mol. Liq. 1992, 52, 181. (5) Shinoda, K. AdV. Colloid Interface Sci. 1992, 41, 81. (6) Perela, L.; Berkowitz, M. L. J. Phys. Chem. 1993, 99, 4222. (7) Degreve, L.; Quitale, C., Jr. Chem. Phys. Lett. 1993. 208, 530. (8) Kuznetsov, An. M. Chem. Phys. 1993, 179, 47. (9) Glasel, J. A. In Water, A comprehensiVe treatise; Franks, F., Ed.; Plenum Press: New York, 1973; Vol. 1, Chapter 6. (10) Zeidler, M. D. In Water, A comprehensiVe treatise; Franks, F., Ed.; Plenum Press: New York, 1973; Vol. 2, Chapter 10. (11) Mizuno, K.; Oda, K.; Maeda, S. ; Shindo, Y. J. Phys. Chem. 1995, 99, 3056. (12) Mizuno, K.; Miyashita, Y.; Shindo, Y.; Ogawa, H. J. Phys. Chem. 1995, 99, 3225. (13) Mizuno, K.; Mabuchi, K.; Miyagawa, T.; Matsuda, N.; Shindo, Y. Abstracts of the 24th IUPAC Conference on Solution Chemistry, Faculty of Sciences, University of Lisbon, Lisbon, Portugal, 1995; p 110. (14) Fister, F.; Herz, H. G. Ber. Bunsenges. Phys. Chem. 1967, 71, 1032.
17O-
and 1H-NMR Studies of Water Structure
(15) Reuber, J. J. Am. Chem. Soc. 1969, 91, 5725. (16) Kuppers, J. R.; Carriker, N. E. J. Magn. Reson. 1971, 5, 73. (17) Harvey, J. M.; Jackson, S. E.; Symons, M. C. R. Chem. Phys. Lett. 1977, 47, 440. (18) Goldammer, E. v.; Herz, H. G. J. Phys. Chem. 1970. 74, 3734. (19) Bagno, A.; Lovato, G.; Scorrano, G; Wijnen, J. W. J. Phys. Chem. 1993, 97, 4601. (20) Uedaira, H.; Uedaira, H. Curr. Topics Solution Chem. 1994, 1, 39. (21) Wen, W.-Y.; Hertz, H. G. J. Solution Chem. 1972, 1, 17.
J. Phys. Chem., Vol. 100, No. 24, 1996 10315 (22) Uedaira, H.; Ikura, M.; Uedaira, H. Bull Chem. Soc. Jpn. 1989, 62, 1. (23) Ishimura, M.; Uedaira, H. Bull. Chem. Soc. Jpn. 1990, 63, 1. (24) Ballinger, P.; Long F. A. J. Am. Chem. Soc. 1960, 82, 795. (25) Mizuno, K,; Kaido, H.; Kimura, K.; Miyamoto, K.; Yoneda, N.; Kawabata, T.; Tsurusaki, T.; Hashizume, N.; Shindo, Y. J. Chem. Soc., Faraday Trans. 1 1984, 80, 879.
JP960194Y
