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Interaction study of some ortho and para amines with 1-octanol.


Spectroscopic technique is a power full tool for the investigate nature of molecular complexes and hydrogen bonding. It is interesting subject to measure various thermodynamic excess functions to obtain molecular association. A number of attempts to develop a quantitatively accurate and physically meaning explanation of solvent induced stretching vibration frequency shifts have been presented [1-4].

In present work, an attempt has been made to study the molecular association between free hydroxyl group of 1-Octanol with different amines group of ortho and Para substitutes of acceptors in Carbon tetra chloride media using FTIR measurements.


A Nicolet Avatar 360 FTIR spectrometer with a resolution of + _ 1 [cm.sup.-1] was used for this study. Spectra were obtained at room temperature (25[degrees]C) in the region of 4000 to 400 [cm.sup.-1.] The chemical used are O-Chloroaniline, O- Methylaniline, O-Methoxyaniline, P-Chloroaniline, P-Methylaniline and P-Methoxyaniline are Aldrich product used without further purification. AR grade of 1-octanol and Carbon tetrachloride were purified by standard procedure [5, 6] and redistilled before used.

Result and discussion

The infrared spectral data of O-Chloroaniline, O-Methylaniline, O-Methoxyaniline, PChloroaniline, P-Methylaniline and P-Methoxyaniline in 1-Octanol are given in table -1. Form the spectrum two hydrogen bonds occur in two regions, due to monomeric and due to polymeric absorption. The proton acceptor of amines concentration is fixed and donor concentration varying from 0.04 is carried out. From table-1, it is noticed that the free amine stretching band increases as the concentration of hydroxyl group increases and the intensity of amine band decreases while half width slightly increases. The observation indicates the 1:1 complex formation between hydroxyl group of 1octanol and the amine group of aniline subsistent. The FTIR spectra obtained using mixed solvent techniques indicates the formation of complexes. It indicates the existence of 1:1 complex

Using Nash method [7], the equilibrium constant (k) for the 1:1 complex is calculated by using equation

K = [AB]/[A][B]

Where [AB] is the concentration of the 1:1 complex and [A] and [B] are the initial concentration of the proton donor and proton acceptor respectively. A graph was plotted between Y = [[A].sup.-1] and X = [[1- - a/[a.sub.0]].sup.-1]. Where a and 0 a are the absorbance of the carbonyl band of aniline substitutes in presence and absence of 1-Octanol respectively. The intercept of the graph in the ordinate yields K-1.

The changes in free energy [8] of systems are calculated using the equation

[DELTA]G = -RT l n k (2)

Where R represents universal gas constant, T represents absolute temperature and k represents formation constant of the systems.

The formation constant and free energy changes values for ortho and Para subsistent of anilines with 1-octanol systems in the inert solvent C[Cl.sub.4] are given in Table 2.

An examination of Table 2 shows that the formation constant for the hydrogen bonded complexes of Ortho and Para aniline with 1-octanol is in the order of P-Methoxyaniline < O-Chloroaniline < O-Methylaniline < O-Methoxyaniline < PChloroaniline. K values for methyl substitute of aniline and chloride substitute of aniline in ortho position are smaller then para substitution of aniline. This shows that complex has greater steric hindrance involving free rotation of molecules. The complex formation is relatively more in 1-octanol [9]. Because of steric hindrance it is likely have greater probability of complex formation due to head tail linkage[10].But for ortho position of methoxy substitute of aniline, formation constant is higher then the para substitute of methoxy substitute of aniline. These reveals that methoxy substitutes of aniline are comes under electron withdrawing groups. The free energy change and formation constant vary with ortho and para substitute of amine with

1-Octanol is suggests that the strength of intermolecular interaction occurs in the ternary mixture. Proton acceptor ability is in the order p-methoxyaniline < ochloroaniline < o-methylaniline < o-methoxyaniline < p-chloroaniline < pmethoxyaniline.


The formation constant and free energy change of ortho and para substitute of aniline with 1-octanol in CCl4 are carried out. From this study one may conclude that the strength of intermolecular bond formed between the ortho and para substitute of aniline and 1-octanol is shown that the tendency of complex formation is relatively more in para substitute than that of ortho substitute of anilines.


[1] R. Navarro, A. Hernanz and I. Bratu, J. Mol. Struct. 348 (1995) 253.

[2] M.C.R. Symons, Chem. Soc. Rev. 12 (1983) 1.

[3] I. Bratu, R. Grecu, R. Constantinescu and T. Iliescu, Spectrochim. Acta Part A 54A (1998) 501.

[4] R. Streck and A.J. Barnes, Spectrochim Acta A 55(5) (1999) 1049.

[5] B. Hernandez, J.M. Gavira-Vallejo, R. Navarro and A. Hernanz, J. Mol. Struct. 565 (2001) 259.

[6] J.R. Riddick and W.B. Bunger, Organic Sovents, Wiley Intersciences, New York (1970)..

[7] C.P. Nash, J Phys. Chem, 64 (1960) 632.

[8] C.R.H. Vinogradov, Hydrogen Bonding, van Nostrand Reinhold Company, new york (1971).

[9] A.K. Chandra and S. Basu, Trans. Frarday Soc. 56 (1960) 632.

[10] J.K. Das, D.K. Dash, S. Acharya and B.B. Swain, Jpn J. Appl. Phys 35 (1996) 453.

M. S. Manjunatha * and J. Sannappa

Department of Physics, Yuvaraja's College, University of Mysore, Mysore-570024, Karnataka, India

* Corresponding author. E-mail:
Table1: Spectral data at 28[degrees]C of 1-Octanol and Ortho
and Para substitution of aniline with C[Cl.sub.4] Solvent.


Proton donor      Proton acceptor      Symmetric     Asymmetric

1-Octanol         O-Chloroaniline        3494           3399
                 O-Methoxyaniline        3485           3393
                  O-Methylaniline        3479           3394
                  P-Chloroaniline        3481           3396
                  P-Methylaniline        3469           3387
                 P-Methoxyaniline        3459           3382

Table 2: Formation constant and free energy change of Ortho and
Para substitution of aniline dissolved in 1-Octanol in inert
solvent C[Cl.sub.4] at 309 k.

                                   Nash method k     -[DELTA]G kcal
Proton donor   Proton acceptor    lit [mol.sup.-1]    [mol.sup.-1]

1-Octanol      O-Chloroaniline         75.00             2.678
               O-Methylaniline          138              3.056
               O-Methoxyaniline        148.38            3.101
               P-Methoxyaniline        50.00             2.426
               P-Chloroaniline          150              3.107
               P-Methylaniline         195.23            3.271
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Author:Manjunatha, M.S.; Sannappa, J.
Publication:International Journal of Applied Chemistry
Article Type:Report
Date:May 1, 2009
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