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Analysis of the self-association of aliphatic alcohols using Fourier Transform Infrared (FT-IR) spectroscopy John T. Reilly, Arun Thomas, Aileen R Gibson, Chi Y Luebehusen, and Marc D Donohue Ind. Eng. Chem. Res., Just Accepted Manuscript • Publication Date (Web): 12 Sep 2013 Downloaded from http://pubs.acs.org on September 12, 2013

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Industrial & Engineering Chemistry Research

Analysis of the self-association of aliphatic alcohols using Fourier Transform Infrared (FT-IR) spectroscopy John T. Reilly, Arun Thomas, Aileen R. Gibson, Chi Y. Luebehusen and Marc D. Donohue

ABSTRACT A number of industrially important systems contain molecules, such as alcohols, that hydrogen bond. To correlate the thermodynamic properties of such systems, assumptions must be made in modeling the chemical equilibrium. It has been found that the data can be fit to a high degree of accuracy if it is assumed that the system contains monomers, dimers, and trimers or tetramers. Alcohols often are modeled by an infinite equilibrium model that takes into account associated species of all sizes. In this model and in others as well, an additional assumption must be made concerning the values of the various equilibrium constants; it usually is assumed that all the equilibrium constants for a given species are equal. In this work, Fourier transform infrared (FT-IR) spectroscopy has been used to study the chemical association of aliphatic alcohols. Analysis of FT-IR spectroscopic data was used to determine the species present in a mixture, the equilibrium constants, and evaluate the validity of the assumptions commonly made. The effect of molecular size on the enthalpic and entropic contributions to the equilibrium constant was determined by analyzing spectroscopic data for alcohols with carbon numbers of 5, 7, and 9 at different temperatures. A qualitative analysis of the spectra revealed that there are at least three types of hydrogen bonds in the mixture. Equilibrium constants, enthalpy and entropy of association, and the absorptivity of the un-associated OH stretch were determined. The equilibrium constants obtained were found to be a function of temperature and chain length.

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INTRODUCTION Over the last several decades, associating fluids have been studied using experimental and theoretical methods (1-24). These fluids are of interest because they are commonly used as solvents, solutes, and entrainers in chemical and pharmaceutical processes. There have been a number of theoretical studies to calculate thermodynamic properties (1-8) of associating systems. These studies have been based on equations of state or activity coefficient models, and explicitly take into account the different species that exist in the solution due to association. Although there have been a number of theoretical studies on associating systems, they have been limited to two kinds of associating molecules. The first approach has been for associating molecules that are spherical or roughly spherical, having one or more association sites (1, 4-8). This can be used to treat molecules like methanol or acetic acid. The second approach has been for polymeric molecules that can be assumed to be made up of segments with each segment having the same number and type of association sites (24). Although these two models can be used to represent a wide range of associating fluids and mixtures, it is useful to study another model for the associating species. In this model the molecules are made up of segments; however, not every segment has association sites. For example, long-chain aliphatic alcohols can bond only at the hydroxyl group. Several studies have been made on associating fluids using infrared spectroscopy (9-17). These studies are based on the measurement of “free” OH-stretch band and the “associated” OH band. Changes in the equilibrium between the “free” and “associated” species due to temperature and concentration have been ascribed with causing the changes in the relative intensities of the absorption bands (9-17). Thus, by quantitatively studying these bands, insight is obtained into the association occurring in the solution. There are numerous models that relate the spectral peaks that are present in alcohol-inert solvent systems to the types of species present. For example, Liddel and Becker (10) investigated the self-association of methanol, ethanol, and t-butanol in carbon tetrachloride and used a monomer-dimer-tetramer model. Tucker and Becker (15) retracted some of Becker's early work on the existence of a dimer, especially one with a frequency of 3550 cm-1. Tucker and Becker (15) took additional measurement of tert-butyl alcohol in hexadecane and found that there is little or no dimer formation and that either an infinite equilibria model or a monomer-trimer-polymer model should be used to describe the self-association of alcohols. Coburn and Grunwald (11) found that a monomer-polymer model best represented their data of 1-octanol in n-decane. Van Ness et al. (13) investigated the self-association of ethanol in n-hexane and toluene. They suggested that the species present when self-association occurs are un-associated monomer, a cyclic (double-bonded) dimer, and polymer ethanol. Most workers have begun their calculations with a priori assumptions of the species present in the mixture. Presented here is work similar to that of Coburn and Grunwald (11) in that the infinite equilibria model is used to fit spectroscopic data after which the model is evaluated. SCOPE OF PRESENT STUDY The primary objective of this paper is to study the effect of chain length on the selfassociation of alcohols. This study involved the determination of the monomer concentrations of the alcohol at very low to low superficial concentrations in n-alkanes having the same number of segments. That is, the mixtures were such that the carbon


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number of the n-alkane is one higher than that for the alcohol in order to have the same number of segments in both species. Therefore, we chose mixtures containing an alcohol of carbon number 5, 7, or 9, and an alkane of carbon number 6, 8, or 10 respectively. Fourier transform infrared (FT-IR) spectroscopy was chosen for this work because it has been shown to be a valuable tool for characterizing mixtures of associating components. When applied to mixtures there are several advantages. FT-IR spectroscopy can be used to show, qualitatively, when hydrogen bonding occurs in a mixture. If there is association occurring in the mixture, distinct spectral changes are apparent. Discussion of these phenomena is given later in this paper. The extent of hydrogen bonding and the chemical equilibrium constant can be determined from a quantitative analysis of the spectral peaks. The chemical equilibrium constant then may be used to predict the phase behavior. THEORY Heidemann and Prausnitz (2) showed that a closed-form equation of state can be obtained for associating systems by assuming a chemical equilibrium for the association taking place. This approach was used by Donohue and co-workers (4-6, 18) to develop the Associated-Perturbed-Anisotropic-Chain Theory and the Acid-Base-Perturbed-Chain Theory which have been used successfully to model the thermodynamic behavior of associating systems. To obtain a closed-form equation of state for associating compounds, the equilibrium expressions and the material balances are solved simultaneously along with an equation of state that is assumed for the individual species. The equilibrium constant is therefore necessary to model the associating compounds. The equilibrium constant can be obtained independently by solving the equilibrium expressions and material balances simultaneously. For a species A that self-associates the chemical equilibrium is written as: Ai  A1  Ai 1

(1)

where A1 is the monomer and Ai is a species of i associated monomers. Equation (1) represents the infinite equilibrium model, where an infinite number of species having 1, 2, n, associated monomers exist in the system. The equilibrium constant for all the reactions are usually assumed to be the same, and is written as:

K AA 

C Ai1

(2)

C Ai C A1

where C Ai are the concentrations of species Ai . The material balance is written as: 

C A0   iC Ai

(3)

i 1

where C A0 is the superficial concentration i.e. the concentration that would exist if no hydrogen bonding took place (moles/liter of compound in the sample). Substituting



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Equation (2) into Equation (3) and using expressions for the summation of geometric series we obtain:

C A0 

C A1

(4)

(1  K AA C A1 ) 2

At the concentrations used here, it is not expected that all the species exist. Therefore, Equation (3) simplifies depending on the species that are assumed to be present. For example, in the monomer-dimer-tetramer model, only the monomer, dimer, and tetramer species are present, and Equation (3) can be simplified to include just three terms. In analyzing spectroscopic data, it is important to recognize that the measurements reflect the association bonds of the system, and not the associated species present in the system. The un-associated band obtained from spectroscopic measurements represents the un-associated OH stretch. The un-associated OH occurs at one end of each polymeric species irrespective of the number of monomers that form the species, and the unassociated band has contributions from all the species present in the mixture. The first associated band is assumed to represent the OH stretch of the OH group that is hydrogen bonded at the Hydrogen site only. This occurs at the other end of all associated species, and the first associated band has contributions from all these species. The second associated peak is assumed to represent the OH stretch of the OH group that is associated at both the Oxygen and Hydrogen sites. This occurs in the interior of associated species that are made up of three or more monomers, and the second associated band has contributions from each of doubly-bonded OH stretches in each of these associated species. This model is schematically represented in Figure 1. For comparison, Figure 2 shows the model used by Van Ness et al. (13) to model ethanol in nhexane. The model shown in Figure 1, assumes that each i-mer has one un-associated OH: therefore, the concentration of un-associated OH, C A can be written as: 

C  C '

A

i 1

Ai



C A1

1  K

C A1

AA



(5)

Equation (5) is used to model the spectroscopic data, and using a non-linear data regression technique, the association equilibrium constant, K AA is obtained. The natural log of K AA is a linear function of inverse temperature and is written as: ln K AA

H 0 S 0   RT R

where H 0 and S 0 are the enthalpy and entropy of association.


(5)

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EXPERIMENTAL APPARATUS AND PROCEDURE Infrared spectra were measured using a Mattson Polaris FT-IR spectrometer using a temperature controlled demountable cell with variable path length. A 0.95 mm Teflon spacer and CaF2 salt crystal windows were used. The temperature of the cell was maintained by circulating heating fluid through the jacket of the infrared cell. The temperature of the cell was measured with a copper-tungsten thermocouple obtained from Omega Engineering. The thermocouple was placed inside the jacket of the cell and connected to an Omega Engineering digital thermocouple thermometer (model 199). The resolution of the digital thermometer is 1 K. Measurement of the heating water varied by 13 K from the measured value of the cell. The uncertainty in the temperature was estimated to be  1 K. Spectrometric grade chemicals were obtained from Aldrich Chemical Company. Pentanol, decane, and octane all had a purity of 99+%. Nonanol had a purity of 99%, heptanol a purity of 98+%, and hexane 95+%. The chemicals were not purified further because purity was checked by infrared spectroscopy and no detectable impurities were found. Infrared spectra were measured for temperatures of 25°C, 30°C and 35°C. Concentrations ranged from 0.005 M to 0.06 M.

EXPERIMENTAL RESULTS FT-IR Spectroscopic Measurements FT-IR spectroscopic measurements were made with three different mixtures of an aliphatic alcohol and hydrocarbon at three different temperatures. Figure 3 shows the spectra of 1-nonanol in n-decane at 30°C for increasing concentration of 1-nonanol. Results similar to Figure 3 for the mixtures of 1-pentanol in n-hexane and 1-heptanol in noctane were obtained but are not shown. Low alcohol concentrations were used. In Figure 3, the spectrum of 1-nonanol/n-decane shows one peak due to the fundamental stretch of the un-associated OH group. When more 1-nonanol is added, several changes occur. First, there is an increase in the intensity of the un-associated band. Second, additional peaks appear and grow in size as the 1-nonanol concentration is increased. These peaks are referred to as the first associated peak and second associated peak. The additional peaks are broad and occur at lower wavenumbers than the un-associated band. As one can see in the spectra in Figure 3, these broad peaks are not present at the lower concentrations and are due to the self-association of 1-nonanol. Third, it appears that at all concentrations there is a shoulder on the low frequency side of the un-associated band. This suggests that the un-associated band is actually a sum of two highly overlapped peaks. In the section to follow, these qualitative observations are quantified using a data analysis technique. Spectral Analysis Concentrations of hydrogen-bonded and un-associated species are determined from the area of the absorption peaks in the infrared spectrum. Beer-Lambert law relates the area to the concentration and path length: (7) ai = kiCil



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in which ai is the area under the absorption peak centered at νi, ki is the absorptivity of the peak at νi, Ci is the concentration and, l is the path length inside the sample cell. In order to determine the concentration of the un-associated band at the higher concentrations it is important that the absorptivity is known. The absorptivity of the un-associated band is determined by taking the slope of the area versus concentration curve at zero concentration. In turn, application of the Beer-Lambert law results in determining the concentration. We turn now to determining the peak areas of each of the spectral bands. Our technique involves a combination of spectral analysis and profile modeling. The spectra are analyzed using Fourier self-deconvolution (18) and differentiation to establish the number and shape of peaks that are present. Profile modeling then is used to determine the height ( h ), peak position (ν0) and, the width parameters (λ, γ) that characterize each peak in the spectrum. These parameters are determined not only by fitting the raw spectroscopic data but also by fitting the derivative and the Fourier self-deconvolution of the data. The shape parameters obtained can be used to reproduce the spectra and therefore, accurately calculate the areas. A more detailed description of this data analysis is given by Reilly et al. (21). As mentioned above, the un-associated band for all of the spectra appeared to have a shoulder on the low frequency side. In addition, all attempts to fit this peak with a single symmetric modeling profile resulted in very poor fits. This qualitative behavior suggested the existence of a second, highly-overlapped peak. In order to explore this possibility a Fourier analysis was performed in which the un-associated band was selfdeconvoluted to improve the resolution of the two peaks. Shown in Figure 4 are the results of deconvoluting the un-associated band. As one can see there is a definite shoulder on the low frequency side. From this we have concluded that the un-associated band is actually the sum of two highly overlapped peaks. In order to accurately model this spectral band it is important to do so with two peaks. The existence of two highly overlapped peaks may be due to different configurations of the aliphatic chain of the alcohols having different effects on the OH bond stretch. In particular, the dihedral bond configuration (trans or gauche  ) of the bond closest to the OH group may have an effect on the OH stretch. DISCUSSION The areas of the un-associated peak for each of the systems at the three different temperatures are shown in Tables 1 - 3. The areas of the un-associated peak for the 1nonanol/n-decane system at the three different temperatures are shown in Figure 5. There are several qualitative features to be discussed. First, as the concentration of the alcohol is increased there is a steady increase in the area of the un-associated band. At the higher concentrations of alcohol the area begins to level off because the formation of hydrogen-bonded species begins to dominate the mixture. Second, at lower concentrations there is very little difference between the areas of the un-associated species at the different temperatures. However, at the higher concentrations, there is generally a 10 to 20% increase in the areas. This is expected because at the higher temperatures an associated species is less stable than at a lower temperature. Third, at the higher concentrations the increase in areas due to temperature for the 1-nonanol is


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higher than those found for either 1-heptanol or 1-pentanol, suggesting an effect due to the carbon number. The areas of the un-associated, 1st associated and 2nd associated peaks for each of the systems at the three different temperatures are shown in Tables 4 - 6. To better understand the growth of the associated species in each mixture, shown in Figure 6 are the areas for the un-associated, first associated, and second associated bands as a function of concentration for 1-nonanol in n-decane at 30°C. As mentioned above, the unassociated band steadily increases until self-association begins to occur. At this point, the first associated band appears and begins to increase as the concentration increases. In addition, the growth of the second associated band does not begin to appear until the concentration is above 0.02 moles/liter after which it increases dramatically as the concentration increases. The association species that were found experimentally indicate at least three types of hydrogen bonds in the mixture. The infinite equilibria model was used to determine the equilibrium constant. As mentioned previously the method involved regressing the enthalpy and entropy of association along with the absorptivity of the un-associated OH band. Reasonable fits of the data are obtained with approximately 5% difference between the fit and the data points. Presented in Table 7 are the equilibrium constant, enthalpy and entropy of association and the absorptivity of the un-associated OH stretch for all of the systems studied. The absorptivity of the un-associated band remains constant with respect to chain length. There is an increase in the absolute value of both the entropy and the enthalpy of association, with both becoming more negative as the chain length increases. The change in the entropy of association due to the increase in chain length was expected as the increase in chain length would change the number of possible configurations and therefore cause the change in the entropy. However, the enthalpy of association was expected to remain constant as this represents the strength of the hydrogen bond, which was not expected to change with chain length. Additional measurements at higher concentrations need to be obtained so that better values for the enthalpy and entropy of association to the association constant can be obtained. Ikonomou and Donohue (4) obtained an enthalpy of association independent of chain length, and an entropy of association that decreased slightly as chain length increased, from regressing experimental vapor pressure and P-V-T data. Since the enthalpy and entropy of association become more negative with increasing chain length, the equilibrium constant was found to decrease as the chain length increased. Similar values of the equilibrium constant for 1-octanol were obtained by Fletcher and Heller (14). CONCLUSIONS Presented in this paper were infrared spectroscopic measurements of aliphatic alcohols in aliphatic hydrocarbons at three different temperatures with increasing concentration of alcohol in the mixtures. A qualitative analysis of the spectra revealed that there are at least three types of hydrogen bonds in the mixture. In addition, the formation of these bonds did not occur until a threshold value of the concentration was reached. For the long chain alcohols we found that the monomeric band was actually a combination of two peaks highly overlapped, even for mixtures with low concentration of alcohol. This suggests that the OH chromophore of the alcohol is in two different configurations for all of



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the concentrations studied. A quantitative analysis of our spectral measurements included an application of the infinite equilibria model. Equilibrium constants, enthalpy and entropy of association, and the absorptivity of the un-associated OH stretch were determined. The equilibrium constants obtained were found to be a function of temperature and chain length. ACKNOWLEDGEMENTS Support of this research by the Division of Chemical Sciences of the office of the Basic Energy Sciences, U.S. Department of Energy under contract no. DE-FG02-87ER13777 is gratefully acknowledged.


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REFERENCES (1) Renon, H.; Prausnitz, J. M. On the thermodynamics of alcohol-hydrocarbon solutions. Chem. Eng. Sci. 1967, 22, 299. (2) Heideman, R.; Prausnitz, J. M. A van der Waals-type equation of state for fluids with associating molecules. Proc. Natl. Acad. Sci. 1976, 73(6),1773. (3) Hu, Y.; Azevado, E.; Ludecke, D: Prausnitz, J.M. Thermodynamics of Associated Solutions: Henry's Constants for Nonpolar Solutes in Water. Fluid Phase Equilibria. 1984, 17, 303. (4) Ikonomou G. D.; Donohue, M. D. Thermodynamics of Hydrogen-Bonded Molecules: The Associated Perturbed Anisotropic Chain Theory. AIChE J. 1986, 32(10), 1716. (5) Ikonomou G. D.; Donohue, M. D. Extension of the Associated Perturbed Anisotropic Chain Theory to mixtures with More Than One Associating Component. Fluid Phase Equilibria. 1988, 39, 129. (6) Economou, I. G.; Ikonomou, G. D.; Vimalchand, P.; Donohue, M. D. Thermodynamics of Lewis Acid-Base Mixtures. AIChE J. 1990, 36, 1851. (7) Economou, I. G.: Donohue, M. D. Chemical, Quasi-Chemical and Perturbation Theories for Associating Fluids. AIChE J. 1991, 37, 1875. (8) Economou, I. G.; Donohue, M. D. Thermodynamic Inconsistencies in and Accuracy of Chemical-Equations of State for Associating Fluids. Ind. Eng. Chem. Res. 1992, 31,1203. (9) Van Thiel, M.; Becker, E. D.; Pimentel, G. C. Infrared Studies of hydrogen Bonding of Methanol by the Matrix Isolation Technique. J. Chem. Phys. 1957, 27(1), 95. (10) Liddel, U.; Becker, E. D. Infra-red spectroscopic studies of hydrogen bonding in methanol, ethanol, t-butanol. Spectrochimica Acta. 1957, 10, 77. (11) Coburn Jr., W. C.; Grunwald, E. Infrared Measurements of the Association of Ethanol in Carbon Tetrachloride. J. Am. Chem. Soc. 1957, 80, 1318. (12) Becker, E. D. Infrared studies of hydrogen bonding in alcohol-base systems. Spectrochimica Acta. 1960, 17, 436. (13) Van Ness, H.; Van Winkle, J.; Richtol, H.; Mullinger, H. Infrared Spectra and the Thermodynamics of Alcohol-Hydrocarbon Systems. J. Phys. Chem. 1967, 71(6), 1483. (14) Fletcher, A.; Heller, C. Self-Association of Alcohols in Nonpolar Solvents. J. Phys. Chem. 1967, 71(12), 3742. (15) Tucker, E. E.; Becker, E. D. Alcohol Association Studies. II. Vapor Pressure, 220MHz Proton Magnetic Resonance, and Infrared Investigations of tert-Butyl Alcohol Association in Hexadecane. J. Phys. Chem. 1973, 77(14), 1783. (16) Duboc, C. Etude par spectrophotometrie i.r. de l'autoassociation de quelques alcools aliphatiques en solution dans le tetrachlorure de carbone-II. Exploitation des mesures d'aires de la large bande. Essai de determination des constantes d'autoassociation. Spectrochimica Acta. 1974, 30A, 441.



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(17) Martinez, S. Methanol/n-hexane system- I. Infrared studies. Spectrochimica Acta. 1986, 42A(4), 531. (18) Walsh, J. M.; Greenfield, M. L.; Ikonomou, G. D.; Donohue, M. D. Hydrogen Bonding Competition in Entrainer Cosolvent Systems. Chem. Eng. Comm. 1989, 86, 124. (19) Bartczak, W. Model of the Self-Association of Primary Alcohols. Ber. Bunsegnes Phys. Chem. 1979, 83, 987. (20) Kauppinen, J. K.; Moffatt, D. J.; Mansch, H. H.; Cameron, D. G. Fourier SelfDeconvolution: A Method for Resolving Intrinsically Overlapped Bands. Applied Spectroscopy. 1981, 35(3), 271. (21) Reilly, J. T.; Walsh,J. M.; Greenfield, M. L.; Donohue, M. D. Analysis of FT-IR Spectroscopic Data: The Voight Profile. Spectrochimica Acta. 1992, 48A(10),1459. (22) Wiehe, I.; Bagley, E. Thermodynamic Properties of Solutions of Alcohols in Inert Solvents. I. and E. C. Fund. 1967, 6(2), 209. (23) Aveyard, R.; Briscoe, B. J.; Chapman, J. Activity Coefficients and Association of Alkanols in Octane. J. C. S. Faraday Trans. I. 1973, 69, 1772. (24) Wertheim, M. S. Fluids of dimerizing hard spheres and fluid mixtures of hard spheres. J. Chem. Phys. 1986, 85, 2929.


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List of Figure Captions Figure 1: Model of the associated species. Figure 2: Van Ness et al. model of ethanol in hexane. Figure 3: Infrared spectrum of 1-nonanol/decane at 30°C as a function of concentration. Three bands are observed, the un-associated or unbounded band at ~3640 cm-1, the first associated band at 3540 cm-1 and, the second associated band at 3340 cm-1. Figure 4: Deconvolution of the un-associated band Figure 5: The areas of the un-associated peak for the 1-nonanol/decane system as a function of the concentration and temperature. Figure 6: The areas of the un-associated, first associated and second associated peaks for the 1-nonanol/decane system as a function of concentration at 30°C.



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Figure 1


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Figure 2 Double-bonded dimer

Monomer

H

H

O

O

H Linear Polymer

O

H

O

H

n

O

H

Cyclic Polymer

O

H

O

H

n

O

H

Water-like structure O O

H

H O

H

H O


O


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Figure 3


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Figure 4



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Figure 5


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Figure 6



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Table 1 Area of un-associated peak of 1-pentanol in n-hexane at 25⁰C, 30⁰C and 35⁰C. Concentration (M)

25⁰C

0.005 0.01 0.015 0.02 0.0225 0.0225 0.026 0.032 0.036 0.042 0.05 0.06 0.08 0.08 0.1 0.1 0.125 0.125 0.15 0.15

0.5933267 1.086314 1.952778 2.398131 2.654553 2.509027 3.331637 4.014555 4.216396 5.057559 5.52576 7.602281 7.433094 8.087883 8.183916 7.662407 8.040832 6.889187 8.072532

30⁰C

35⁰C

1.179149 1.853809 2.280573 2.709153

0.6731299 1.386888 2.021339 2.518138 2.923827

3.200136 3.887349 3.912733 4.922228 5.441676 6.480641 8.846857 7.918803 8.598977 8.162398 9.744339 8.588622 8.263463 7.883102

3.394418 3.795048 4.210278 5.172586 5.20831 6.599602 8.624481 8.898491 9.302114 10.00769 9.613271 9.876538 10.114237 10.458784


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2 Area of un-associated peak of 1-heptanol in n-octane at 25⁰C, 30⁰C and 35⁰C. Concentration (M) 0.005 0.01 0.015 0.02 0.0225 0.0225 0.026 0.032 0.036 0.042 0.05 0.06 0.08 0.08 0.1 0.1 0.125 0.125 0.15 0.15

25⁰C 0.4953673 0.9492478 1.626626 2.047544 2.21982 2.637385 2.758798 3.365212 3.78019 4.229353 4.613516 5.139392 6.881967 7.168674 6.665376 7.628807 7.274601 8.452536 6.754761 7.936173

30⁰C 0.1812105 0.966245 1.634321 2.063999 1.943759

35⁰C 0.7971742 1.333844 1.932578 2.448584 2.617377

3.031805 3.867752 3.762896 4.511066 4.969433 5.334738 7.542959 7.668972 8.09034 8.120397 7.920802 8.37807 8.109167 7.968593

3.250747 3.661228 4.207078 4.524211 5.256531 5.972494 7.881959 8.81261 8.990741 9.662326 9.668862 10.851628 9.674781 9.970823



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Table 3 Area of un-associated peak of 1-nonanol in n-decane at 25⁰C, 30⁰C and 35⁰C. Concentration (M) 0.01 0.015 0.02 0.0225 0.0225 0.026 0.032 0.036 0.042 0.05 0.06 0.08 0.08 0.1 0.1 0.125 0.125 0.15 0.15

25⁰C 1.076895 1.594533 1.799309 1.960019 2.387193 3.031644 3.170979 3.295294 3.519154 3.961375 4.139517 6.793828 7.488891 7.367179 7.632749 7.834922 7.867395 8.123527 7.583997

30⁰C 0.4588321 1.041747 1.824002 2.266522

35⁰C 1.031802 1.682607 2.184379 2.459921

2.896551 3.103751 3.334296 4.014911 4.451075 4.817057 7.390371 7.687727 7.50949 8.527621 8.281677 8.695221 8.50389 8.485016

3.265678 3.40621 3.941695 4.518348 5.242559 5.198148 8.09833 8.12383 8.619609 9.337363 9.074337 9.224727 10.051082 10.743482


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 4 Area of un-associated, 1st associated and, 2nd associated peaks of 1-pentanol in n-hexane at 30⁰C. Concentration (M) 0.005 0.01 0.015 0.02 0.0225 0.01 0.015 0.02 0.0225 0.026 0.032 0.036 0.042 0.05 0.06 0.08 0.08 0.1 0.1 0.125 0.125 0.15 0.15

Un-associated Peak 0.9019868 1.853832 3.569768 3.849718 3.742066 2.163247 3.410618 3.906678 4.5663 5.050837 5.693513 5.997405 6.538112 7.59871 8.69313 8.846857 7.918803 8.598977 8.162398 9.744439 8.588622 8.263463 7.883102

1st Associated peak

0.610944 0.722303 0.401565 0.151308 0.243989 0.998824 1.226803 0.699491 1.208867 1.306026 1.979712 2.452244 3.260326 2.709024 2.68556 3.483562 3.260492 5.084022 4.06356 3.041864 2.968956


2nd Associated peak

1.57364 3.761726 4.243084 7.694154 15.40821 23.59968 31.00409 29.54093


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Table 5 Area of un-associated, 1st associated and, 2nd associated peaks of 1-heptanol in n-octane at 30⁰C. Concentration (M) 0.005 0.01 0.015 0.02 0.0225 0.005 0.01 0.015 0.02 0.0225 0.026 0.032 0.036 0.042 0.05 0.06 0.08 0.08 0.1 0.1 0.125 0.125 0.15 0.15

Un-associated Peak 1.025689 1.707803 2.363671 2.900258 3.135781 0.970541 1.89298 2.82178 3.533115 3.930063 4.974507 5.709461 6.390672 7.062196 7.649736 9.036082 7.542959 7.668972 8.09034 8.120397 7.921402 8.37807 8.109167 7.968583

1st Associated peak

2nd Associated peak

0.213658 0.545938 0.52545 1.313705 0.512744 0.821539 0.957412 0.844482 0.843815 1.444175 1.687028 2.291582 2.922426 3.537595 3.999438 3.822276 4.497601 4.49407 2.445801 2.984707 3.514345 3.37658


5.952416 4.395236 7.35621 12.362 21.99106 39.21163 35.07204

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 6 Area of un-associated, 1st associated and, 2nd associated peaks of 1-nonanol in n-decane at 30⁰C. Concentration (M) 0.005 0.01 0.015 0.02 0.0225 0.005 0.01 0.015 0.02 0.0225 0.026 0.032 0.036 0.042 0.05 0.06 0.08 0.08 0.1 0.1 0.125 0.125 0.15 0.15

Unassociated Peak 0.906463 1.803577 2.47352 3.105694 3.455797 1.319097 2.204751 3.06875 4.251342 3.784329 4.097335 4.924469 5.007276 5.974633 6.681053 7.788185 7.390371 7.687727 7.50949 8.527621 8.281677 8.695221 8.50389 8.485016

1st Associated peak

2nd Associated peak

0.262332 0.396414 0.555095 0.629943 0.326588 0.853198 0.730681 0.679509 0.954517 0.996925 1.406376 2.160444 3.47341 3.251373 2.889961 4.254087 3.79047 4.032229 4.250172 4.09123 4.03512


2.652579 2.609159 3.52047 7.06738 8.569529 10.76496 16.41417 32.8452 41.5686


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Table 7 Equilibrium constant, enthalpy and entropy of association and absorptivity of the un-associated OH stretch obtained from data regression. SAMPLE 1-pentanol in n-hexane 1-heptanol in n-octane 1-nonanol in n-decane

 0 ( 0 )

174.8 178.6 177.0

H 0 kcal / mol -4.25 -5.46 -6.72


S 0 / R -5.12 -6.42 -8.50

K AA ( x 10-6) 4.58 0.162 0.0024

(FT-IR) Spectroscopy - American Chemical Society

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