Vibrational spectroscopic studies of aqueous
`solutions of tert-butyl alcohol and tert-butylamine
`
`Pius K. Kipkemboi and Allan J. Easteal
`
`
`789
`
`Abstract: Raman and FT—IR absorption spectra of aqueous tert—butyl alcohol (t—BuOH) and tert—butylamine (t—BuNHz)
`in the region of the 0—H and NH2 stretching and bending modes have been measured as a function of organic co-
`solvent concentration in the whole co-solvent mole fraction region. The major observed changes of the aqueous binary
`solution spectra compared with the solvent spectra are a loss or gain of band intensity. In particular, the observed
`changes in intensities and linewidths of some bands were significantly more pronounced at low concentrations of or-
`ganic co-solvents in water, where t-BuOH and t—BuNH2 tend to integrate into the water structure. Clear evidence of
`structural enhancement of the network is obtained in dilute solutions as well as destruction of the network by hydro-
`phobic interactions as the concentration is increased. Generally, the interpretation of the spectra is in agreement with
`the capacity of the hydrophobic co-solvent to break the structure of water in the more concentrated aqueous solutions
`and to enhance the structure in dilute solutions. Vibrational intensities and frequency shifts of some bands show defi-
`nite trends with varying the concentration of the solutions. In the concentration-dependence study, unusual linewidth
`changes of certain bands were observed.
`
`Key words: infrared, Raman spectra, aqueous, tert-butanol, tert-butylamine.
`
`Résumé 2 On a mesuré les spectres d’absorption Raman et infrarouges en transformée de Fourier de solutions aqueuses
`de tert—butanol (t—BuOH) et de tert—butylamine (t—BuNHZ), dans la région des modes d’élongation et de deformation du
`O—H et du NHZ, en fonction de la concentration du cosolvant organique, sur toute la plage des fractions molaires du
`cosolvant. Les changements principaux observe’s dans les spectres en solutions aqueuses binaires par rapport a ceux des
`spectres du solvant sont des gains ou des pertes dans l’intensité de la bande. En particulier, les changements observés
`dans les intensités et les largeurs de quelques bandes sont beaucoup plus prononcés a de faibles concentrations des
`cosolvants organiques dans l’eau vers laquelle le t—BuOH et la t-BuNH2 ont tendance de migrer dans la structure de
`l’eau. On a obtenu des données claires en faveur d’une augmentation de la structure du re'seau en solutions diluées
`ainsi que de la destruction du re’seau par les interactions hydrophobes avec une augmentation de la concentration. En
`ge'ne’ral, l’interpre’tation des spectres est en accord avec la capacité du cosolvant hydrophobe a briser la structure de
`l’eau dans les solutions aqueuses plus concentre’es et a les augmenter en solutions diluées. Les intensités vibrationnelles
`et les déplacements dans les fréquences de quelques bandes présentent des tendances bien définies avec les variations
`dans les concentrations dans les solutions. Dans l’étude sur la dépendance sur la concentration, on a observé des
`changements inhabituels dans la largueur de certaines bandes.
`
`Mots cIés : infrarouge, spectre Raman, aqueux, tert—butanol, tert-butylamine.
`
`[Traduit par la Re’daction]
`
`Introduction
`
`Vibration spectra are, in general, sensitive to the local en-
`vironment of a molecule, and information concerning the
`relative position of the molecule in quite a short time can be
`obtained from the spectra. Vibrational spectra of water or
`aqueous solutions have received considerable attention in re-
`lation to the liquid structure of water. Although numerous
`papers have been presented reporting spectra of inorganic
`electrolytes in aqueous solution, there are few studies on the
`
`Received 14 December 2001. Published on the NRC Research
`Press Web site at http://canjchem.nrc.ca on 20 June 2002.
`.
`.
`_1
`.
`'
`.
`P-K- Kipkembm- Department Of Chemls'fl'y, M01 UanerSltY:
`PO. Box 1125, Eldoret, Kenya,
`A.J. Easteal. Department of Chemistry, The University of
`Auckland, Private Bag 92019, Auckland, New Zealand.
`
`1Corresponding author (e-mail: keronei@yahoo.com).
`
`vibrational spectra of organic molecules in water (1—10). It
`is of interest to interpret vibrational spectra of organic mole-
`cules in aqueous solution and to discuss the intermolecular
`interactions and liquid structures in the these systems.
`In the present investigation, FT—IR and Raman spectra of
`aqueous tert—butanol and tert-butylamine in the 0—H stretch-
`ing and bending regions were measured at room temperature
`as a function of co-solvent concentration in the entire co-
`
`solvent mole fraction region. The purpose of this study was
`to investigate the structural changes brought about by a
`change in the concentration of co-solvent. It was anticipated
`.
`that FT'IR and Raman SPeCtI‘OSCOpy of aqueous solutlons of
`the aforementioned compounds would provide insights into
`the structural perturbations of bulk water, which are caused
`by hydrophobic co-solvents, and provide a structure-oriented
`conceptual framework for evaluating various hydrophobic
`effects. In the present study, the two co-solvents, tert—butyl
`alcohol (t—BuOH) and tert—butylamine (t—BuNHZ), were used
`
`Can. J. Chem. 80: 789—795 (2002)
`
`DOI: 10.1139N02-102
`
`© 2002 NRC Canada
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`Merck Exhibit 2234, Page 1
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`Merck Exhibit 2234, Page 1
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`RamanIntensity
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`
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`Wavenumber (cm'l)
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`1000
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`2000
`
`3000
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`2000 3000 3200
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`3400 3600 3800
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`3000
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`3200
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`3400
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`
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`Ramanintensity
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`Absorbance
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`Wavenumber (cm'l)
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`Wavenumber (cm'l)
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`1000
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`2000
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`3000
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`1400
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`1600
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`Absorbance
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`Ramanintensity
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`Wavenumber (cm'l)
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`Wavenumber (cm-1)
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`Bandintensity
`
`20
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`4o
`
`60
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`80
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`M01 % t-BuNH2
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`
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`Ramanintensity
`
`3000
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`Wavenumbers (cm'l)
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`100
`
`3500
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`
`
`mewmw
`(011171)
`3294
`3294
`3294
`3294
`3296
`3296
`3296
`3296
`3296
`3296
`3298
`3300
`3305
`3310
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`Wavenumber (cm'l)
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`0W 3
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` I
`
`I
`
`l
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`Absorbance
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`Absorbance
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`
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`0
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`100
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`r—Tfi—r
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`3000
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`3500
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`Wavenumber (cm-1)
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`1200 1300 1400 1500 1600 1700
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`Kipkemboi and Easteal
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`Acknowledgments
`
`The authors are indebted to the New Zealand government
`for the award of a Commonwealth Scholarship to Pius
`Kipkemboi, and to the University of Auckland Research
`Committee for equipment funding.
`
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`© 2002 NRC Canada
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`Merck Exhibit 2234, Page 7
`Mylan v. Merck, |PR2020-00040
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`Merck Exhibit 2234, Page 7
`Mylan v. Merck, IPR2020-00040
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