J. Phys. Chem. 1993, 97, 13335-13340
13335
Excited-State Proton Transfer from Hydroxyalkylnaphtholsf Laren M. Tolbert,' Lilia Cuesta Harvey, and Rachel C. Lum School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400 Received: July 8, 19930
The excited-state proton-transfer (ESPT) reactions of 1-propyl-2-naphthol(PN), 1-(3-hydroxypropyl)..2-naphthol (HPN), and 1-(2,3-dihydroxypropy1)-2-naphthol(DPN) in aqueous methanol solutions have been investigated. The hydroxypropyl and dihydroxypropyl side chains have a pronounced effect on the rate of the proton transfer and on the number of water molecules involved, indicating that proton transfer in alcoholic solvents is more complex than simple models of water clusters can accommodate. Alternative models in which a side chain facilitates the formation of the requisite geometry for proton transfer are discussed.
Introduction The critical role of proton transfer as one of the most fundamental chemical processes has elicited numerous groundand excited-state investigations. The mechanisticdetailsof proton transfer to water, however, remain surprisingly elusive. Chief among the methods for studying the dynamics of this process has been the time-resolved spectroscopy of naphthol derivatives. Both 1- and 2-naphthol undergo pKa (Ferster) shifts upon photoexcitation, with the result that, at neutral pH in aqueous solution, naphthols exist in their neutral form in the ground state but exist largely as their conjugate base in the first excited singlet state.' Since the neutral and conjugate base excited-state forms are emissive,the evolution of solvated neutral to solvated anion within the lifetime of the excited state has provided a practical subject for time-resolved spectroscopic investigation of both proton transfer and solvent reorganization. The work of Robinson has provided much of our understanding of the dynamics of excited-state proton transfer to water,*while at the same time fueling a controversy over the details of the mechanism. The general approach used by Robinson and others is to investigate the fluorescence decay of the neutral, or fluorescence rise time of the anion, as a function of water concentration in a miscible but nonbasic cosolvent. Typically, the cosolvent is methanol or ethanol. The increase in the neutral decay rate as a function of increasing water concentration is associated with proton transfer to water, a conclusion which is generally supported by the observation of anion rise in concert with neutral decay. In the alcoholic solventsreported,' the increase in decay rate exhibits higher than first order dependence upon water concentration. A statistical analysis using a Markov random walk method of the increase in decay rate upon increasing water concentration led Robinson to propose that a water cluster of order 4 f 1 was required for proton transfer to This cluster size is maintained not only for neutral 1-naphthol4and 2-naphthol3 but also for anionic 1-naphthol-2-sulfonatesand the cationic 6-methoxyquinolinium ions6 Although the intervention of water clusters as proton acceptors in proton transfer reactions has been invoked in many contexts, the structures of the solvent cluster and its protonated form remain unknown. Certainly, the solvated proton within a tetrahedral shell of water molecules provides a compelling structure, but the possibility of more extended hydrogen-bonded networks cannot be excluded. Moreover, our observation that more acidic naphthols such as 5-cyano2-naphthol can transfer protons to methanol in the absence of water7 belies the absolute requirement for water as a proton acceptor. Dedicatedto the memory of Gerhard Claw-teacher, scholar,and friend. *Abstract published in Aduancr ACS Absrracrs. November 15, 1993.
The requirement for a water cluster as proton acceptor has been adopted by others, including Shizuka.8 Huppert and coworkers, however, have developed a somewhat different model emphasizing the effectsof solutes on water activity.9 The kinetics in the presence of ionic solutes can be readily expressed by the formula shown in eq 1 (or, in logarithmic form, eq 2), where kd is the decay rate in ionic aqueous media, ko is the decay rate in pure water, a(H2O) is the activity of water, and n is an order parameter which may be roughly associated with the number of water molecules involved in the proton transfer step.
h(kd) = ln(ko) 4- n ln[a(H20)] Although eq 2 has some superficial similarity with Robinson's proposed model, Agmon, Huppert, Masad, and Pinesloultimately reject the water cluster model of Robinson, ascribing instead the major effect of increasing water concentration to more efficient solvation of the conjugate base and proposing a mechanism apparently involving solvation of a single hydronium ion by methanol or water. In order to develop a better understanding of the geometric requirements for solvation of the incipient proton, we elected to investigatenaphthols which incorporated an alkyl chain containing a varying number of hydroxyl groups, which would reduce the degrees of freedom in the proton-transfer reaction and would provide insight into the structure of the transition state. We chose to study excited state proton transfer in 1-(3-hydroxypropyl)-2-naphthol (HPN), 1-(2,3-dihydroxypropy1)-2-naphthol (DPN), and, as a reference, 1-propyl-2-naphthol (PN). The results of these studies are, we propose, in consonance with the Huppert mechanism and with a structure in which solvation of the hydronium ion is rate-limiting. Results. Synthesis of Substrates The desired substrateswere conveniently prepared from 1-allyl2-naphthol (AN), which was obtained by Claisen rearrangement of the requisite allylnaphthyl ether (see Figure 1). Catalytic hydrogenation of AN yielded PN, hydroboration and hydrogen peroxide deboronation of AN yielded HPN, and osmium tetroxide bishydroxylation of AN yielded DPN. All substrates provided unambiguous spectra and exact masses. Results. Steady-State Fluorescence Measurements Initial fluorescencemeasurements were carried out in methanol and methanollwater mixtures. All substituted naphthols exhibited similar fluorescence properties, with emission maxima in pure methanol of 362-364 nm correspondingto excitation maxima at 289 nm. Upon addition of water, a new emission at 441444
0022-365419312097-13335$04.00/0 0 1993 American Chemical Society
Tolbert et al.
13336 The Journal of Physical Chemistry, Vol. 97, No. 50, 1993
0
AN
.3
2
Be
U 3
2
PN
HPN
DPN
0.00
Figure 1. Synthesis of propylnaphthols PN, HPN, and DPN,
335
435
535
h, nm Figure 4. Effect of water on the emission of 1-(2,3-dihydroxypropyl)2-naphthol (DPN) in methanol. Arrows indicate increasing water concentration in increments of 0.1 from 0.0 to 0.9 volume fraction.
l6'O1
335
435
535
h, nm
DPN
Figure 2. Effect of water on the emission of 1-propyl-2-naphthol(PN) in methanol. Arrows indicateincreasingwater concentrationin increments of 0.1 from 0.0 to 0.9 volume fraction.
- HPN 0 PN @
7.0 ! 0.0
I
0.2
0.4
0.6
0.8
1
1 .o
Vol. Fraction [H20]
F i p e 5. Dependence of the rate constant for neutral decay on water concentration for (a) PN, (b) HPN, and (c) DPN. Solid lina represent the best fit to eq 3. Dashed lines represent best fits to eqs 4 and 5 (see
text).
1
335
435
535
h, nm Figure 3. Effect of water on the emission of 1-(3-hydroxypropyl)-2naphthol (HPN) in methanol. Arrows indicate increasing water concentration in increments of 0.1 from 0.0 to 0.9 volume fraction.
nm was observed. The magnitude of the shift in emissionmaxima was consistent with the prototropic behavior of naphthols, and we conclude that the emissions at 363 and 443 nm correspond to the singlet excited states of neutral (naphthol) and anion (naphtholate), respectively. Most significantly, the intensity of the anion emission increased with hydroxy substitution (compare Figures 2, 3, and 4). Results. Time-Resolved Fluorescence Measurements The distinction between neutral and anion emission in the three naphthol derivatives allowed an investigation of the dynamics of neutral decay, anion formation, and anion decay through timecorrelated single photon counting. The decay of the neutral emission at ca. 360 nm in all three naphthols could be readily
reconstructed through an iterative deconvolution procedure involving the sum of two exponentials, indicating the presence of a major "slow" decay process kd and a minor "fast" decay process kd'. As the amount of water in methanol/water solutions was increased, the decay rate of the neutral increased (see Figure 5 ) . This increase in neutral decay rate, however, was associated with increases in the major decay rate constant kd only (see Tables 1-111). An investigation of the dependence of the minor decay pathway on emission wavelength indicated a significant wavelength dependence. As with the neutral decay, the anion decay associated with the ca. 440-nm emission could be simulated through the use of three exponentials. One exponent was accompanied by a negative preexponential factor and thus corresponded to the rate of proton transfer k, to form the anion excited state, while the remaining two exponents k& and kb' corresponded to the decay of anion excited state. As was the case for neutral decay, the "slow" process in anion decay k& was the dominant component. The anion rise time was a function of water concentration, with increasing water content producing faster anion formation for PN and HPN (see Figure 6). The statistics for DPN were not sufficient to ascertain a trend in the anion rise time. However, the slow component of the anion decay for all three naphthols exhibited very little change as a function of water concentration (see Figure 7). The decay of the neutrals in aqueous methanol solutions exhibited a nonlinear dependence upon water concentration, as shown in Figure 5 . A simple preassociation model for water cluster formation involving a cluster of order 4 would be expected to produce a simple fourth-order dependence on water concen-
The Journal of Physical Chemistry, Vo1. 97, No. 50, 1993 13337
Hydroxyalkylnaphthols
TABLE I: Fluorescence Lifetimes of 1-Propyl-2-naphtbolin Water/Methanol Mixtures’ 96 H206 kd kd‘ kP( 0 10 20 30 40 50 60 70 80 90
7.6 f 0.1 (91) 7.5 f 0.1 (86) 7.7 f 0.1 (91) 7.9 f 0.1 (92) 7.8 f 0.1 (85) 8.2 0.1 (87) 8.7 f 0.1 (87) 9.2 f 0.1 (84) 10.7 0.3 (85) 12.1 f 0.2 (77)
60.0 f 42.0 (9) 62.5 f 53.6 (14) 87.9 f 51.4 (9) 80.8f 43.9 (8) 78.0 f 71.2 (15) 1 1 1.4 f 95.4 (13) 91.9 f 56.6 (13) 86.0 h 67.6 (16) 84.7 f 45.4 (15) 93.2 f 76.1 (23)
*
Rates are in units of
lo7 s-l.
7.3 f 0.3 8.0 f 0.4 9.2f 0.1 9.7 f 1.4 10.8 f 1.1
k&
kbf
5.6 f 0.3 (98) 5.7 f 0.4 (99) 5.8 f 0.5 (99) 5.4f 0.4 (99) 5.8f 0.6 (100)
590 f 230 (2) 520 f 320 (1) 400*300(1) 570 f 30 (1) 690 f 00 (0)
The percent contribution is listed in parentheses. Percentage of water is measured by volume.
TABLE Ik Fluorescence Lifetimes of l-(%-Hydroxypropyl)-2-naphth0l in Water/Methanol Mixtures’ kd 8.0f 0.1 (94) 8.2f 0.0 (92) 8.5 f 0.1 (96) 8.4 f 0.3 (90) 8.6f 0.2 (90) 9.1 f 0.0(93) 9.4 f 0.1 (93) 10.1 f 0.1 (92) 11.4 f 0.4(90) 13.0 f 0.6(89)
5% H206
0 10 20 30 40 50 60 70 80 90 4
Rates are in units of
lo7 s-l.
kdf 40.4 f 13.7(6) 48.8 f 25.0(8) 71.9f 15.4 (4) 67.8f 44.0 (10) 56.1 f 45.1 (10) 78.9f 40.3 (7) 60.2 24.7 (7) 42.9 f 19.8 (8) 52.5 f 18.7 (10) 60.6 f 24.0 (1 1)
*
kpl
kb
k&’
7.9 f 0.3 8.3 f 0.3 9.4 f 0.5 10.2 f 0.7 11.4f 0.9
5.7f 0.2 (99) 5.8 f 0.1 (100) 5.6f 0.0 (97) 5.8f 0.1 (100) 5.8 f 0.1 (99)
480 f 360 (1) 34000 f 29000 (0) 130 f 170 (3) 550 f 260 (0) 100 f 60 (1)
The percent contribution is listed in parentheses. b Percentage of water is measured by volume.
TABLE IIk Fluorescence Lifetimes of l-(2,1Dibydroxypropy1)-2-~ph~ol in Water/Methanol Mixtures’ 9.6f 0.3 (92) 9.7 f 0.0(92) 9.8 f 0.4(92( 10.2 f 0.1 (86) 10.7 f 0.1 (62) 11.0fO.1(81) 1 1.7f 0.2 (88) 12.5f 0.4 (83) 13.7f 0.1 (93) 15.4 f 0.9 (76)
0 10 20 30 40 50 60 70 80 90 4
Rates are in units of
79.1 f 24.2 (8) 79.7f 43.9 (8) 46.1 f 12.8 (8) 110.0 f 145.3 (14) 153.1 f 139.9 (38) 152.9 f 126.4 (19) 132.5f 142.2 (12) 138.2 f 138.2(17) 178.8 f 176.9 (7) 115.2 f 149.0(24)
17.3f 6.8 14.9f 1.7 21.4f 10.1 16.6 f 3.1 14.9 f 1.8
lo7 s-*. The percent contribution is listed in parentheses.
22.0-
6.6 f 0.2(97) 7.0 f 0.5 (96) 6.3f 0.2(97) 6.8A 0.2 (85) 7.0f 0.1 (82)
520 f 160 (3) 380 f 200 (4) 500 f 17 (3) 320 f 290 (15) 170 f 230 (18)
Percentage of water is measured by volume. 8.01
0
19.00
c
0
0
16.0-
(4
0
cn
0
13.0X
e
v Y
10.0-
e 0
O
8
e
(4
0
6
5.01
7.04.0 0.4
e
0
(b)
0 I
I
0.6
0.8
DPN HPN PN I
1.o
4.01 0.4
I
I
0.5
3
l
0.7
0.6
I
1
0.8
0
DPN HPN PN 1
0.9
1
1.0
Vol. Fraction [H20]
Figure 7. Dependence of the rate constant for anion d a y on water concentration in aqueous methanol for (a) PN, (b) HPN, and (c) DPN.
+ k,[H 0 kd = ko k,[H OI 3 kd ko + kw[H20] 12 k d = ko
+
(3) (4) (5)
Discussion. Analysis of Fluorescence Spectra and h y Kinetics The steady-state fluorescence measurements indicate an increasing progression in anion emission from propyl- to hydroxypropyl- to dihydroxypropylnaphthols. A cursory exami-
13338 The Journal of Physical Chemistry, Vol. 97, No. 50, 1993 nation would lead to the conclusion that hydroxy groups facilitate the deprotonation of the naphthol during the lifetimeof the excited state. Such conclusions, based upon steady-state measurements, must be supported by the underlying rate constants. Due to the complexity of solvation of the 2-naphthol molecule, the singlet decay of naphthols does not lend itself to simple firstorder exponential analysis. Thus the decay kinetics have been modeled by multiple exponentials" and by power law dependence.10 All of these methods involve considerable manipulation of data and assumptions about the nature of the decay kinetics when two (or more) emitting species are involved. Such assumptions and manipulations make comparison of the various models for naphthol decay a daunting task, particularly since the use of one or more models to successfully simulate kinetic data is not prima facie evidence that the correct decay kinetics have been identified. Nevertheless, our approach was to use the model involving the fewest assumptions, that is, a double exponential in the case of neutral decay, or, in order to account for anion rise, a triple exponential. This approach involved no assumptionsabout themagnitudeof the rateconstants,"Jnor did it requiresubtraction of anion decay from neutral decay.1° This treatment invariably gave excellent residuals, with x* < 2. A minor fast component of neutral decay was invariant with respect to water concentration. This same component was emission wavelength dependent, suggesting the presence of a minor decay pathway not dependent upon water but which involved, perhaps, a neutral with a different hydrogen-bonding environment. Therefore, the discussion is limited to the water-dependent component. A difficulty addressed by Robinson's treatment of the data for 2-naphthol' was a consequence of the nonmonotonic dependence of the decay of photoexcited 2-naphthol on water concentration. The absence of such behavior in the propylnaphthols PN, HPN, and DPN allowed us to take a more direct approach. The possibility of a cluster of four water molecules as a proton acceptor suggested that a simple kinetic model provided by eq 3 could account for the behavior of our naphthols. However, only PN exhibited a decay dependenceupon water which could be modeled by this equation (see solid lines in Figure 5 ) . In contrast, HPN could be modeled by an equation involving only a third-order dependence, eq 4, while DPN could be modeled most effectively by an equation involving a second-order dependence, eq 5 (see dashed lines in Figure 5 ) . This second- and third-order dependence suggested that water trimers and dimers are involved in the proton-transfer reaction. Clearly, the apparent dependence of the water molecularity upon the nature of the side chain provides a provocative topic for debate. Discussion. The Role of Water in Naphthol Deprotonations The proposal by Robinson for preformation of a cluster of 4 f 1water molecules before proton transfer takes place has intuitive
appeal, since it anticipates the thermodynamic driving force for formation of a solvation shell around the proton during the transition state. This rationalization presents a conundrum, however, since gas-phase determinations of the proton affinity of methanol and water indicate that the former is higher by 15 kcal/mol.Iz In fact, Meot-Ner has found13 that the preference for solvation by methanol of the proton does not diminish for cluster sizes of up to seven solvent molecules. In contrast, Garvey and co-workers have observed the presence of "magic numbers" for the formation of methanol/H30+ clusters and suggest the highest stability for hydronium ion surrounded by a series of nine methanol molecules forming five-membered rings.14 More recently, Karpas and co-workers have disputed the claims of Garvey, citing possible differences in the conditions under which ions are formed and dissociate.15 Nonetheless, it is prudent when discussing the dynamics of proton transfer in solution to discuss the relevance of gas-phase cluster data. Obviously, two differences between the gas-phase cluster data and the solution-phase proton-transfer data are evident. First,
Tolbert et al. H
H
Figure 8. Possible geometry for proton transfer in DPN.
the former deals with the thermodynamics of the solvated proton, while the latter deals with the kinetics. Therefore, the cluster with greatest stability may not be the most efficiently formed. Meot-Ner made an attempt to recognize this fact by observing that "clusters grow by attachment to hydrogen, and HjO+ in the center allows branched structures which place more molecules near the charged center."" This picture also fits neatly with the cluster model proposed by Garvey.1' This difference between thermodynamic and kinetic effects in solution has been discussed in different terms by Suwaiyan et al." They have suggested that solvent clustering may operate for proton transfer from poor excited-state proton donors, e.g., 2-naphthol or the naphthols discussed here, while solvent reorientation is dominant for strong excited-state proton donors. A second difference is the extrapolation from a proton within a finite solvent cluster to a fully solvatedproton in aqueous solution. Stace et a1.,16for instance,observe that the preference for solvation of the proton by methanol shifts to water at an approximate cluster size of 8-10, Thus in bulk solution, the formation of hydrogen bonds to water by hydronium may occur at the expense of the formation of hydrogen bonds to methanol, which introduces an anomalous preference for solvation of the proton by water rather than by methanol. In our case, the effect of a hydroxyl substituent on an internally solvating side chain is, paradoxically, to increase the effect of water on the deprotonation rate, apparently facilitating proton transfer at smaller cluster sizes. This effect is incompatible with a simpledynamicmodel in which water serially replaces methanol in the proton solvent shell, leading to proton transfer only when the cluster size of four water molecules is reached. That is, this simple model would also imply that the decrease in entropy required for displacement of an intramolecularly, as opposed to intermolecularly, hydrogen-bonded solvent molecule would lead to a decreased, rather than increased, deprotonation rate. Our results are compatible, however, with a model in which a proton is transferred to a single water molecule, forming a hydronium ion solvated both intra- and intermolecularly by alcohol moieties and thus increasing the rate of proton transfer in the presence of increased hydroxylation of the side chain (see Figure 8). Conclusions The proton-transfer dynamics of photoexcited hydroxyarenes continues to provide a rich source of information on topological and solvolytic effects on proton transfer. The presence of one or more hydroxy groups on an alkyl side chain incorporated into the photoacid facilitates the proton transfer to water in methanol solution. We conclude that the excited-state proton-transfer reaction in aqueous alcohols must occur with intimate participation of the alcoholic solvent. Further insight can be gained by use of hydroxyarenes which do not require water for efficient proton transfer. Such studies are in progress. Experimental Section Materials. 1 -Propyl-2-naphthol (PN) , 1- (3-hydroxypropyl)2-naphthol (HPN), and 1-(2,3-dihydroxypropy1)-2-naphthol (DPN) were synthesized as described below. All naphthol derivatives were purified by recrystallization (from petroleum ether or hexanes) and/or by sublimation' before use in the spectroscopic experiments. Spectrophotometric grade (99.9%
Hydroxyalkylnaphthols pure) or HPLC grade (99.9+% pure) methanol (Aldrich) and HPLC grade water (Aldrich) were used as received. Fluorescence Spectra. Fluorescence spectra were recorded using a SPEX Model F112X spectrofluorometerequipped with a xenon arc lamp and a single grating excitation monochromator. Sample fluorescence was collected at right angles from the excitation beam, and monochromator entrance and exit slit widths were set at 1.O nm. All spectra were corrected for the wavelength dependence of the photomultiplier response using a rhodamine B quantum counter. Data were collected every 1.0 nm. Solutions used in the fluorescence experiments were prepared in 5- or IO-mL volumetric flasks and then transferred to longneck quartz cuvettes fitted with rubber septa. For the water quenching studies, the concentration of fluorophore was held constant while varying the water volume fraction in methanol solvent from 0.0 to 0.9. The solutions were purged with a solventsaturated inert gas, typically argon, for 20 min prior to spectral acquisition. Concentrations were maintained between 10-4and 10-5M. Spectra were acquired at ambienttemperature. Emission spectra were obtained with the excitation monochromator set at 289 nm. Fluorescence quantum yields were obtained from the ratio of fluorescence intensity with and without water. Fluorescence Lifetimes. Excited-statelifetimes were measured at ambient temperature using a time-correlated single photon countingfluorometerwhich has been describedprevi0us1y.l~The nanosecond lamp comprised tungsten electrodes which were set 1-3 mm apart and operated under a nitrogen atmosphere. The lamp voltage was typically maintained between 3.2 and 3.4 kV. To minimize interference from stray light, Hoya filters were used for the monitoring of sample fluorescence; filter UV-36 was used for neutral emission while an L-37 was used for anion emission. Lamp profiles were measured using a scattering sample, consisting of a drop of milk in about 5 mL of distilled water, while both the excitation and emission monochromators were set at 338 nm. When the data for the sample were collected, the emission monochromator settings were set to the fluorescence emission maxima for the neutral or the anionicspecies. Lamp and sample data were acquired until 10000 data points were collected. Fluorescence lifetimes were determined by an iterative deconvolution technique using both the lamp scattering profile and the sample emission data. Samples for fluorescencelifetime measurements were prepared in the same manner as those for the steady-state experiments. Sampleconcentrations were between 1Wand 10-5M. All samples were deoxygenated with methanol-saturated argon for at least 25 min before use in the single photon counting experiment. All ultraviolet and visible spectra were acquired with a Gilford Response spectrophotometer. Spectra were obtained using a 1-nm instrumental bandpass and a scan increment of 0.5 nm. Nuclear magnetic resonance spectra were acquired with a Varian Gemini 300 MHz spectrometer. Mass spectra were obtained using a VG Analytical 70-SE spectrometer. GC/MS analyses were conducted with a Hewlett-Packard5890 gas chromatographequipped with a DB-5 column interfaced with the mass spectrometer. l-Propyl-2-naphthol(PN). l-Allyl-2-naphtho11*(0.245 g, 1.33 mmol) was dissolved in 30 mL of ethyl acetate followed by addition of 0.0779 g of palladium on carbon. Hydrogen was introduced into the reaction flaskviaan externallatex balloon and the reaction mixture purged three times with hydrogen before starting the reduction. After 24 h, filtration and column chromatography (SiOz, 10% ethyl ether in hexanes) yielded 1-propyl-2-naphthol (PN) in 81%yield (0.202 g, 4.09 mmol). The spectral data were as follows: 1H NMR (300 MHz, CDC13) 6 1.03 (3 H, t), 6 1.67 (2 H, m), 6 2.98 (2 H, t), 6 4.91 (1 H, s), 6 7.04 (1 HI d, J = 8.8 Hz), 6 7.30 (1 H, t), 6 7.45 (1 H, t), 6 7.61 (1 H, d, J = 8.8 Hz), 6 7.76 (1 H, d, J = 8.24 Hz), 6 7.92 (1 H, d, J = 8.6 Hz); MS m/z (re1 intensity) 187 (8), 186 (SO), 157 (loo), 141 (S), 129 (27), 115 (9). Anal. Calcd for C13H140: 186.1045. Found: 186.1043.
The Journal of Physical Chemistry, Vol. 97, No. 50, 1993 13339
1-(3-Hydroxypropyl)-2-naphtl10l (HPN). 1-Allyl-2-naphthol (3.07 g, 0.0167 mol) was flushed with argon for 45 min in a dry reaction vessel, followed by addition of 25 mL of distilled tetrahydrofuran. Boranetetrahydrofuran complex (8.12 mL of a 1 M solution, 6.12 mmol) was transferred to the reaction flask over a I5 min period. After 75 min with stirring, water (0.65 mL) was added followed by 6 mL of 3 M NaOH. Hydrogen peroxide (30%, 3.4 mL) was added over 15 min, during which the reaction temperature was not allowed to exceed 50 OC. The reaction mixture was warmed to 45 OC for 45 min, then added to 100mL of saturated ammoniumsulfate solution, and extracted with ether (3 X 50mL). Thecombinedether extracts werewashed twice with water (200 mL), dried over MgS04, and concentrated in vacuo. The residue was recrystallized from hexanes to yield 2.53 g (12.5 mmol, 75%) of 1-(3-hydroxypropyl)-2-naphthol (HPN), mp 125-127 OC. The spectral data were as follows: 'H NMR (300 MHz, acetone-&) 6 1.86 (2 H, m), 6 2.84 (1 H, s), 6 3.16 (2 H, t), 6 3.60 (2 HI t), 6 7.17 (1 HI d, J = 8.8 Hz), 6 7.27 (1 H, t), 6 7.43 (1 H, t), 6 7.64 (1 H, d, J = 8.9 Hz), 6 7.77 (1 H, d, J = 8.2 Hz), 6 7.99 (1 H, d, J = 8.8 Hz); MS m/z (relative intensity) 203 (14), 202 ( 7 9 , 184 (36), 183 (16), 169 (33), 158 (23), 157 (loo), 156 (12), 144 (14), 141 (12), 129 (48), 128 (51), 127 (23), 115 (21), 102 (5). Anal. Calcd for C13H1402: 202.0994. Found 202.0996. 1-(2,3-Dihydroxypropyl)-2-naphthol (DPN).Os04 (8.6 mg, 0.034 mmol) and N-methylmorpholine N-oxide (0.453 g, 3.86 mmol) was added to 10 mL of water, 4.5 mL of acetone, and 2 mL of tert-butyl alcohol. To this mixture 0.686 g (3.73 mmol) of 1-allyl-2-naphtholwas added. After 24 hat room temperature under argon, a slurry of 0.5 g of sodium hydrosulfite and 2 g of fluorisil in 20 mL of water was added to the reaction mixture. The mixture was filtered and the filtrate neutralized to pH 7 with 1 N HzSO4. The acetone was removed via rotary evaporation and the pH further adjusted to 2. The solution was treated with saturated ammonium sulfate and extracted with ethyl acetate. The combined organic fractions were dried over MgS04,and the solvent was removed to yield a yellow oil. The product was purified by recrystallization from hexanes to yield 0.545 g (2.50 mmol, 67%) of 1-(2,3-dihydroxypropyl)-2-naphthol (DPN), mp 124126 OC. Thespectral data wereas follows: 'H NMR (300 MHz, acetone-d6)63.14(1H,dd,J=7.1H z , J = 14.3Hz),3.34(1 HI dd, J = 5.5 Hz, J = 14.3 Hz), 3.50 (1 H, dd, J = 5.0 Hz, J = 1 0 . 6 H z ) , 3 . 6 1 ( 1 H , d d , J = 4 . 5 H z , J = 10.7Hz),4.02-4.11 (2 H, m), 4.66 (1 H, s), 7.16 (1 H, d, J = 8.8 Hz), 7.28 (1 H, t), 7.44 (1 H, t), 7.68 (1 H, d, J = 8.8 Hz), 7.79 (1 H, d, J = 8.1 Hz), 8.03 (1 H, d, J = 8.8 Hz), 8.89 (1 H, s); MS ( m/z (relative intensity) 219 (8), 218 (46), 169 (17), 158 (70), 157 (loo), 156 (6), 144 ( l l ) , 141 (17), 129 (51), 128 (48), 127 (20), 115 (19), 102 (5). Anal. Calcd for C13H1403: 218.0943. Found: 218.0941. Acknowledgment. Support of this research by the National Science Foundation through Grant CHE-9111768 is gratefully acknowledged. References and Notes (1) For reviews, see: (a) Weller, A. Prog. Rcoct. Kinct. 1%1,1,187. (b) Ireland, J. F.; Wyatt, P. A. H. Adu. Phys. Org. Chem. 1976, 12, 131. (2) See,for example: Robinson, G. W.; Thistlethwaite, P. J.; Lee,J. J .
Phys. Chem. 1986, 90,4224. (3) Lee,J.; Griffin, R. D.; Robinson, G. W. J . Chcm. Phys. 1985, 82, 4920. (4) Lee,J.; Robinson, G. W.; Webb, S. P.; Philip, L.A.; Clark, J. H. J . Am. Chcm. Soc. 1986, 108,6538. (5) Krishnan,R.; Fil1ingim.T. G.;Lee,J.; Robinson,G. W. J. Am. Chem. Soc. 1990, 112, 1353. (6) Yao, G. H.; Lee,J.; Robinson, G. W. J . Am. Chem. Soc. 1990,112, 5698. (7) Tolbert, L. M.; Haubrich, J. E. J . Am. Chem. Soc. 1990,112,8163.
13340 The Journal of Physical Chemistry, Vol. 97, No. 50, 1993 (8) (a) Shizuka, H. Acc. Chem. Res. 1985,18,141. (b) Shmka, H.; Kamcta, K.;Shinozaki, T.J. Am. Chem. Soc. 1985,107,3956.(c) Shizuka, H.;Sefkwa, M.J . P h p . Chem. 1986,90,4573.(d) Shizuka, H.;Serhwa, M.; Okazaki, K.; Shioya, S . J. Phys. Chem. 1986,90,4694. (9) Huppert, D.;Kolodney, E.; Gutman, M.; Nachliel, E.J . Am. Chem. Soc. 1982, 104,6949.
(lo) Agmon’ N’; Huppert’ D’;Masad’ A’; 95,10407.
E’ J‘ phys’
1991’
(1 1) Suwaiyan, A,; AI-Adel, F.; Hamdan, A.; Klein, U. K. A. J. Phys. Chem. 1990,94,7423. (12) Lias, S. G.;Liebman, J. F.; Levin, R.D. J. Phys. Chem. Ref Data
1984,13.695.
Tolbert et al. (13) Meot-Ner (Mautner), M.J . Am. Chem. Soc. 1986,108,6189. (14) Herron, W.J.; Coolbaugh, M. T.;Vaidyanathan, G.; Peifer, W.R.; Gamey, J. F. J . Am, Chem. sm.1992,114,3684. (15) Karpas, Z.; Eiceman, G. A.; Harden, C. S.;Ewing, R.G. J. Am. Soc. Mass sPecrrom, 1993,4, 507. (16) (a) Stace, A. J.; Shukla, A. K. J. Am. Chem. Soc. 1982,104,5314. (b) Stace, A. J,; Moore, C. J , p h p . Chem. 1982,86,3681. (c) Stam, A. J.; Moore* c*J* Am* Chem* lW39 Io’* 1814. (17) Tolbert, L. M.; Ntsselroth, S . M. J. Phys. Chem. 1991,95,10331. (18) Marcinkiewicz, S.;Green, J.; Mamalis, P. Tetrahedron 1961,14,
208.
