Solvent effects on OH stretching frequencies for 1-arylallyl alcohols

Article abstract of DOI:10.1016/S1386-1425(01)00591-1

A series of 1-arylallyl alcohols were prepared and its OH stretching frequencies measured in 20 different non-HBD solvents at room temperature. It is noticed that the observed stretching bands were highly sensitive to the nature of the solvents. Multiple

Full text of DOI:10.1016/S1386-1425(01)00591-1

Spectrochimica Acta Part A 58 (2002) 1437–1442
www.elsevier.com/locate/saa
Solvent effects on OH stretching frequencies for 1-arylallyl
alcohols
Salim Y. Hanna *, Moafaq Y. Shandala, Salim M. Khalil
Department of Chemistry, College of Science, Uni6ersity of Mosul, Mosul, Iraq
Received 3 March 2001; received in revised form 18 July 2001; accepted 23 July 2001
Abstract
A series of 1-arylallyl alcohols were prepared and its OH stretching frequencies measured in 20 different non-HBD
solvents at room temperature. It is noticed that the observed stretching bands were highly sensitive to the nature of
the solvents. Multiple parameter equations were applied to investigate the solvent effects on the OꢀH stretching
frequency. The most significant solvent parameters were the nucleophilicity measuring parameter (B) and Gutmann
donor number (DN), whilst the electrophilicity measuring parameter (E) is not significant. © 2002 Elsevier Science
B.V. All rights reserved.
Keywords: Solvent effects; Allyl alcohols; Infrared spectroscopy
The OꢀH stretching vibration of an alcohol in
dilute solution is affected by intra- and inter-
1. Introduction
molecular interactions, the former depends on the
It is generally found that the position, intensity,
molecular structure of the alcohol only, and mea-
and shape of absorption bands are usually influ-
surements in the gas phase can give information
enced by solvents of different polarity [1,2].
on this type of interaction [4]. The latter interac-
These modifications are a result of inter-molec-
tion roughly depends on the type of solvent and
ular solute–solvent interaction forces, such as
the molecular structure of the alcohol.
ion–dipole, dipole–dipole, dipole-induced dipole,
and hydrogen bonding which will tend to alter the
Intra- and inter-molecular hydrogen bonding
results in a downward frequency shift and a very
energy difference between ground and excited
considerable broadening and intensification of the
state of the absorbing species containing the chro-
OꢀH absorption band [5,6]. Solvents interact with
mophore [3].
alcohol molecules through a bulk effect with the
molecule as a whole and through local interaction
with the hydroxy group. In principle, the local
* Corresponding author. Present address: Department of
solute–solvent interaction can occur either
Chemistry, College of Science, University of Nasser, PO Box
through association with the hydroxyl H-atom or
through the oxygen lone pair [7].
40191, Alkhoms, Libya.
E-mail address: syh1@maktoob.com (S.Y. Hanna).
1386-1425/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S1386-1425(01)00591-1

1438
S.Y. Hanna et al. / Spectrochimica Acta Part A 58 (2002) 1437–1442
Much attention has been paid to the chemistry
NaHCO3, and finally with water, dried, and dis-
tilled. Acetone and ethylmethylketone (EMK)
were refluxed with KMnO4, then distilled. MeCN,
MeNO2, DMF, and DMSO were spectroscopic
grade. 1,4-Dioxane was refluxed over sodium until
sodium became bright, then distilled. Tetrahydro-
furan (THF) was refluxed with LiAlH4, then dis-
tilled. Diethylether (DEE) and toluene (PhMe)
were dried with sodium then distilled, anisole
(PhOMe) was shaked with 2 M NaOH then with
water, dried, and distilled over sodium.
of allylic compounds because of their great syn-
thetic utilities, and their widely theoretical studies
[8].
In the present work, we investigate the solvent
effect on the infrared (IR) stretching frequencies
of OꢀH for a series of 1-arylallyl alcohols (Scheme
1).
Various multiple-parameter equations were ap-
plied to explain the solvent effects [9–11].
2. Experimental
2.1. Infrared spectra
2.3. General procedure for preparation of
1-arylallyl alcohols
The IR spectra were measured with a Pye-
Unicam SP 3-200 and Perkin–Elmer 580B spec-
trophotometer. Scan time was 10 and 20 min,
respectively, using ‘liquid’ cells with sodium chlo-
ride windows, an equivalent cell with the pure
solvent was used in the compensating beam. The
concentration of the alcohol solutions usually was
in the range of 0.04–0.06 M, between these limits
the OH stretching frequencies showed no concen-
tration dependence. In general, the frequencies
Substituted bromobenzene (0.1 mol) dissolved
in dry diethyl ether, 75 ml in a dropping funnel,
few drops of it were added to a suspension of
magnesium (0.1 mol) and iodine crystals in dry
DEE (75 ml). The reaction mixture was stirred
until the iodine color disappeared, then the whole
substituted bromobenzene solution was added
dropwise, the reaction mixture was boiled until all
magnesium reacted. After cooling with ice.
Freshly distilled acroleine (0.1 mol) in dry DEE
(50 ml) was added dropwise during 2 h, in ice
bath, stirring was continued for 12 h. The magne-
sium salt was then decomposed with an ice-cold
saturated aqueous solution of ammonium chlo-
ride, the ether layer was washed twice with water
and dried with MgSO4, the DEE was evaporated,
and the crude product was fractionally distilled
under reduced pressure; the middle fraction was
redistilled and used in this study.
reported are accurate within 91 cm−1
.
2.2. Sol6ent purifications
Solvents were purified by standard methods
[12], and stored in dark bottles over molecular
,
sieves type 4 A. n-Hexane, cyclohexane, benzene
(PhH), bromobenzene (PhBr), chlorobenzene
(PhCl), CHCl3, CCl4, CH2Cl2, ClCH2CH2Cl and
Cl3CCH3, were washed with conc. H2SO4, 10%
Scheme 1.

S.Y. Hanna et al. / Spectrochimica Acta Part A 58 (2002) 1437–1442
1439
Table 1
The OꢀH stretching frequencies of eight 1-arylallyl alcohols in 20 different solvents
Number
Solvent
w¯ OH (cm−1) for substituted 1-phenylallyl alcohols
Sub. ꢁH
p-MeO
m-MeO
p-Me
m-Me
p-Cl
o-MeOa
o-Me
1
2
3
4
5
6
7
8
n-Hexane
Cyclohexane
CC14
CHC13
CH2Cl2
(CH2Cl)2
C13CCH3
PhH
PhMe
PhCl
PhOMe
1,4-Dioxane
DEE
3621
3624
3615
3595
3583
3584
3604
3574
3582
3590
3526
3457
3453
3439
3511
3555
3224
3460
3343
3295
3620
3617
3614
3592
3593
3576
3605
3577
3576
3585
3507
3453
3445
3442
3517
3550
3425
3485
3345
3245
3624
3621
3620
3595
3586
3580
3603
3582
3575
3583
3512
3422
3432
3424
3492
3541
3410
3482
3318
3248
3621
3619
3617
3594
3587
3580
3597
3578
3578
3587
3508
3440
3455
3408
3487
3545
3425
3475
3352
3295
3624
3620
3612
3590
3587
3578
3597
3575
3577
3584
3497
3410
3430
3433
3492
3548
3535
3495
3335
3280
3625
3624
3616
3590
3585
3582
3605
3575
3572
3585
3500
3410
3425
3424
3470
3535
3432
3480
3260
3215
3628
3628
3621
3605
3601
3602
3601
3583
3586
3584
3507
3469
3469
3442
3496
3567
3514
3531
3310
3277
3626
3622
3621
3601
3590
3585
3605
3575
3578
3580
3495
3426
3460
3390
3490
3552
3464
3475
3300
3270
9
10
11
12
13
14
15
16
17
18
19
20
THF
MeCN
MeNO2
Acetone
EMK
DMF
DMSO
m=45–140 mol−1 l cm−1; w1/2=0.2–0.3 cm−1 for solvents number 1–10 while m=120–360 mol−1 l cm−1; w1/2=0.8–6 cm−1 for
solvents number 11–20.
a The second absorption band appears in solvents (1–7) at 3584, 3592, 3561, 3565, 3565, 3554, and 3560 cm−1, respectively.
3. Results and discussion
atom and the rotation of the OH group around
CꢀO axis which can be either free or partially
hindered, accordingly leading to a few energeti-
cally favorable conformations.
The calculated heats of formation (DHf) for the
different conformations of 1-phenylallyl alcohol,
using MINDO-forces program 13, are shown in
Scheme 2.
MINDO-forces approximation based on
MINDO/2 approximation using MINDO/3
parameters for core repulsion functions, and en-
ergy was minimized as a function of geometry
using Pulay’s force method [13].
The OꢀH stretching frequencies of eight 1-aryl-
allyl alcohols (Scheme 1) measured at room
temperature in 20 different solvents are listed in
Table 1.
In general, as the solvent polarity increases the
observed absorption band becomes broader and
more intense, this can be attributed to the increas-
ing polarity of OꢀH bond, which might, therefore,
be expected to show a greater difference between
the OꢀH bond dipole moment in the ground and
excited state.
The observed shapes of the OꢀH stretching
were symmetric, asymmetric, with a shoulder or
well splitted (Fig. 1). These effects can be ex-
plained either on the basis of intra- and inter-
molecular hydrogen bonding, the presence of a
second band caused by Fermi-resonance with the
combination band of the a-CH group, or the
oxygen lone pair interaction with a hydrogen
It can be seen from the calculated heats of
formation that the rotational barrier is easily
overcome at room temperature. Hence, alcohols
in solution can be present in many different
conformations.
It can be seen from Table 1 that w¯ values for the
alcohols in the same solvent are almost constant.
This can be explained by either the skeleton is

1440
S.Y. Hanna et al. / Spectrochimica Acta Part A 58 (2002) 1437–1442
always present in the same favorable conforma-
tion or that the different orientations about the
CꢀC axis have no effect on the OH stretching
frequency.
On the other hand, plotting the OH stretching
frequency of one of the phenylallyl alcohols
against the OH stretching frequency of other sub-
stituted phenylallyl alcohols in different solvents
gives a good linear correlation (0.970r00.99),
indicating that the solvents interact with the OH
groups of all arylallyl alcohols by the same inter-
action mechanism.
1-(o-Methoxyphenyl) allyl alcohol shows two
peak maxima in the OꢀH stretching region in
solvents number 1–7 (Table 1; Fig. 1). This obser-
vation is due to presence of at least two conform-
ers, freely and intra-molecular hydrogen-bonded.
Scheme 2. Newman projection along the CꢀO bond of 1-
phenylallyl alcohols showing different rotamers and their heats
of formation.
Scheme 3. Newman projection along the CꢀO of 1-(o-
methoxyphenyl) allyl alcohol showing different rotamers and
its heats of formation.
The calculated heats of formation for different
conformations of 1-(o-methoxyphenyl) allyl alco-
hol are shown in Scheme 3, which clearly indi-
cates the presence of two conformers. In
non-polar aromatic solvents, such as PhH and
PhMe, only one absorption maximum is ob-
served. This indicates that the free conformers
Fig. 1. Part of the IR spectrum of 1-(-o-methoxyphenyl) allyl
alcohol in (A) n-hexane, (B) CC14, (C) CHCl3, (D) PhH, and
(E) 1,4-dioxane.

S.Y. Hanna et al. / Spectrochimica Acta Part A 58 (2002) 1437–1442
1441
were associated with the p-electrons of the aro-
matic solvents forming (p···HO) inter-molecular
hydrogen bonding, which appears in the same
region of (O···HO) hydrogen bonds.
firstly the basicity measuring parameters B, i, and
donor number (DN), then the dipolarity-polariz-
ability measuring parameters Y, P, y* and ET,
and finally the acidity measuring parameter E and
h. The sequence of solvent parameters indicates
that major effecting parameters were the basicity
measuring parameters and the minor effecting
parameters the acidity measuring parameters.
The negative sign of B, i, DN, y*, Y, and ET
coefficients indicate the inverse proportionality of
these parameters with OꢀH stretching frequencies
(Tables 2–4). This means that, as the basicity of
the solvent increases the OꢀH stretching fre-
quency decreases, due to formation of a stronger
hydrogen bond between the solvent and the OꢀH
hydrogen atom. On the other hand, as the polar-
The IR-spectroscopic data of Table 1 were
treated statistically in terms of generalized multi-
ple parameter correlation equations, which split
the gross solvent effects into separate independent
contributions corresponding to different type of
solvent–solute interaction mechanism. Tables 2–4
represent Koppel–Palm, Taft–Kamlet, and
Krygowski–Fawcett equations [9–11], analysis
results from multiple regression of OH stretching
frequencies.
The sequence of importance of solvent parame-
ters during the stepwise regression analysis were
Table 2
Correlation analysis of w¯ OH for substituted 1-arylallyl alcohols using the Koppel–Palm equation [9]
Subst.
w¯ =C+eE+bB+yY=pPa
R
C
E
B
y
p
H
3698.7935.0
3739.4944.1
3718.7937.8
3709.3925.5
3718.9931.1
3750.3950.1
3778.4955.3
3754.7935.9
0.00392.6
−1.2493.2
−2.4192.8
−08591.82
−3.0492.3
−4.8993.7
−1.8594.1
−1.2892.6
−1.8090.1
−1.9290.12
−2.0490.11
−1.8390.07
−1.9490.09
−2.290.14
−1.990.16
−2.0590.1
−63.73950.2
−38.9963.2
−32.13954.2
−54.1935.2
+11.78944.6
−20.4971.9
−24.8979.3
−27.3951.5
−39.429138.9
−273.19174.9
−122.279149.9
−109.3997.4
−220.591 23.4
−241.79199.0
−399.49219.4
−296.49142.4
0.97
0.95
0.97
0.98
0.98
0.96
0.93
0.97
p-MeO
m-MeO
p-Me
m-Me
p-Cl
o-MeO
o-Me
a w¯and C represent the parameters A and A0 in the original equation, the E and B terms represent the solvents electrophilicity and
nucleophilicity. The Y and P terms represent functions of the solvents dielectric and polarizability respectively.
Table 3
Correlation analysis of w¯ OH for substituted 1-arylallyl alcohols using the Kamlet–Taft equation [11]
Subst.
w¯ =C+s(y*−0.38l)+bi+aha
r
C
s
b
A
H
3621.9196.96
3621.99911.2
3624.3910.5
3618.497.2
3615.9911.5
3628.5913.6
3630.2915.2
3624.4910.5
−64.57923.24
−79.14937.4
−79.5935.0
−66.4924.1
−68.3938.4
−94.1935.5
−79.9950.8
−84.4935.0
−311.4925.9
−308.8941.8
−336.79.2
−311.1926.9
−313.2942.9
−357.9950.8
−291.2956.8
−324.5939.1
75.4944.0
117.5970.9
96.9966.4
74.3945.6
95.2972.7
108.0986.2
124.8996.3
126.3966.4
0.97
0.94
0.95
0.97
0.94
0.94
0.89
0.95
p-MeO
m-MeO
p-Me
m-Me
p-Cl
o-MeO
o-Me
a w¯ and C represent the parameter XYZ and XYZ0 in the original equation, y* a scale of the solvents dipolarity-polarizability, h
and i represent a scale of the solvents hydrogen bonding donor and acceptor capability, respectively.

1442
S.Y. Hanna et al. / Spectrochimica Acta Part A 58 (2002) 1437–1442
Table 4
Correlation analysis of w¯ OH for substituted 1-arylallyl alcohols using the Krygowski–Fawcett equation [10]
Subst.
w¯ =C+hET+iDNa
r
C
h
i
H
3692.5942.3
3679.1951.4
3706.3942.5
3696.8929.8
3672.8942.0
3728.5956.2
3696.4962.3
3690.3944.2
−2.9091.10
−2.4991.30
−3.3191.13
−3.0990.79
−2.4591.12
−3.9491.50
−2.6691.66
−2.8091.13
−1.8490.11
−1.9690.11
−2.0690.12
−1.8590.08
−1.9490.11
−2.2092.20
−1.8990.17
−2.0690.13
0.96
0.94
0.97
0.96
0.95
0.95
0.92
0.96
p-MeO
m-MeO
p-Me
m-Me
p-Cl
o-MeO
o-Me
a w¯ and C represent Q and Q0 in the original equation, ET and DN represent the solvents Dimroth–Reichardt constant and the
DN, respectively.
ity of the solvent increases the OꢀH stretching
frequency decreases, this is due to a stronger
polarization of OꢀH bond which leads to a de-
crease of the OH bond force constant.
The positive sign of the hydrogen bonding
donor parameter (h) coefficients indicates its
direct proportionality to the OꢀH stretching
frequency, which means that, as the acidity of
the solvent increases, the stronger interaction
with the oxygen lone pair of the hydroxyl group
leads to an increase in the OꢀH stretching fre-
quency.
References
[1] C. Reichardt, Chem. Rev. 94 (1994) 2319 references cited
therein.
[2] T. Hensel, J. Fruwert, K. Dathe, Collect. Czech. Chem.
Commun. 52 (1987) 22.
[3] C. Reichardt, Solvents and Solvent Effects in Organic
Chemistry, second ed., VCH, Weinheim, 1988 completely
revised ed.
[4] L.J. Bellamy, The Infrared Spectra of Complex
Molecules, third ed., Wiley, New York, 1975.
[5] F.A.J. Singelenberg, E.T.G. Lutz, J.H. Van der Maas,
Vibrational Spectroscopy 1 (1991) 311.
[6] F.A.J. Singelenberg, E.T.G. Lutz, J.H. Van der Maas, J.
Mol. Struct. 245 (1991) 173.
[7] (a) J.F. Bacon, J.H. Van der Maas, J. Chem. Soc., Perkin
Trans. 2 (1988) 1805;
The electrophilicity measuring parameter (E) is
a non-significant parameter because its coefficient
value is lower than its standard error Table 2.
(b) F.A.J. Singelenberg, J.H. Van der Maas, J. Mol.
Struct. 240 (1990) 213.
[8] (a) R.K. Mackie, D.M. Smith, R.A. Aitken, Guidebook
to Organic Synthesis, second ed., Longman, UK, 1990;
(b) Y. Jean, F. Volotron, An Introduction to Molecular
Orbitals, Oxford University Press, New York, 1993 J.
Burdett, Trans.
4. Summary
[9] I.A. Koppel, A.V. Palm, in: N.B. Chapman, J. Shorter
(Eds.), Advances in Linear Free Energy Relationship,
Plenum Press, London, 1972 Chapter 5.
[10] T.M. Krygowski, W.R. Fawcett, J. Am. Chem. Soc. 97
(1975) 2143.
[11] R.W. Taft, J.-L.M. Abboud, M.J. Kamlet, J. Org. Chem.
49 (1984) 2001.
[12] D.D. Perrin, W.L.E. Armarego, D.R. Perrin, Purification
of Laboratory Chemicals, Pergamon Press, Oxford, 1980.
[13] S.M. Khalil, M. Shanshal, Theoret. Chim. Acta (Berl.) 46
(1977) 23.
Twenty non-HBD solvents effect on the OꢀH
stretching frequency of eight phenyl substituted
1-phenylallyl alchohols were performed. The
quantitative description of the solvent effects by
mean of correlation analysis with three well-
known multiparameter equations were carried
out. The three applied multiparameter equation
describe the solvent effects approximately to equal
extent.