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## Journal of the Chilean Chemical Society

*versión On-line* ISSN 0717-9707

### J. Chil. Chem. Soc. v.53 n.3 Concepción sep. 2008

#### http://dx.doi.org/10.4067/S0717-97072008000300008

J. Chil. Chem. Soc, 53, N° 3 (2008) págs: 1588-1593
In this paper, we find that stretching vibration frequencies of the X=0 for series of R
Since the Wienerindex Bajaj Sanjay Recently, the study on quantitative structure-spectrum relationship (QSSR) has attracted widespread attention.
In this paper, we consider using the ionicityindices of atoms in X=0 to depict the change rule of the spectral property of compounds with X=0 and build a múltiple linear regression (MLR) model as follows: where a, b, c are regression constant.
Authors ever pointed the ionicityindices ( ^{22} of atoms in molecule asIn the Equation (2), Xis the atomic equilibrium electronegativity_{E} ^{23} in molecule. Xis figured as_{E} In the Equation (3), Σ1 is the sum of atoms or branching groups directly attached to the atom, and ΣX ^{24}:As shown in Fig. 1, the group can be divided into n are the sum of the ground atom / and other atoms or groups directly attached to the ground atoms in the grade are the sum of electronegativities of the ground atom / and other atoms or branching groups directly attached to the ground atoms inthe grade 1, 2, _{21} ...n_{kl}3,...k.
Scientists began to research into the infrared spectrum in the 20th century. Ordinarily, the infrared absorption frequency of the organism is in the range of 4000-625 cm
There are many factors influencing on the displacement of the absorption bands, for example, the electronic effect, stereoscopic effect, coupling effect, bond strength, tautomery, hydrogen bond. Researchers found out that the change of the stretching vibration frequencies of the X=0 bond is mostly determined by the electronic and stereoscopic factors We made linear simulation of the stretching vibration frequencies of the X=0 for various series according to the Equation (5) using the known infrared spectrum data We calculated the stretching vibration frequencies of the X=0 for 35 compounds by the Equation (6)-(1 1), and listed the results on the Table 1.The results indicated that the stretching vibration frequencies of the X=0 were well correlated with the ionicityindices of the atom O and X, the correlation coefficient The calculated values and the experimental values are depictured on Fig. 2. We can see that the calculated values fit closely with the experimental ones. To further prove the stability of the model, we used the LOO method to test the Equation (5). In this method S could be used to test the stability and validity of the model. We tested the Equation (6) and Equation (9) by LOO method._{cv}For series R The results showed that the method using Equation (5) to study the stretching vibration frequencies of the X=0 was rational and credible.
The stretching vibration frequency of the C=0 for α-halogenated aldehyde becomes larger, becΔυse the a-H atom is substituted by the halogen atom with larger electronegativity. The influence order of the halogens is F>Cl>Br>I. In addition, the change of the stretching vibration frequencies of the C=0 (Δυ) has relation to the number of the substituted a-H atoms. In this paper, we studied the law of change of Δυ for α-halogenated aldehyde. According to Equation (5), we obtain Equation (14)-Equation (15) we get
Based on Equation (16), We studied the relationship between the values of Δυ The experimental values and the calculated ones are listed on Table 2. The result illustrated that Equation (17) better opened out the change of the stretching vibration frequencies of the C=0 for series α-halogenated aldehydes. In fact, the ionicityindex denotes the electronegativity variation between the neutral atom and the bonded atom in a molecule. The more largely electronegativity varíes, the higher ionicity level of the atoms is. Forming a molecule, the electronegativity variations of the atoms in diverse chemical conditions are different too. Therefore the ionicityindices of the atoms are different from each other. All above lead to the different stretching vibration frequencies of the X=0 (υ).
The ultraviolet absorption spectrum is one of the four important spectrums in structural analysis for organic compound. Researchers are eagerly looking forward to describing the change rule of the ultraviolet absorption spectrum quantificationally. As we known, the ketone is non-conjugated compound. For the carbonyl (C=0) of ketones (R We do the regression analysis with The experimental value of the ultraviolet absorption wavelength (λ) is from reference Both the calculated values and the experimental values are Usted on Table 3. From the result, we find that most of the absolute errors from this work are less than that of ref 32. From Fig.3, it is obviously that the calculated values accord well with the experimental ones. The Equiation (19) was tested by LO method: From the high INI_{(C)} , INI_{(O)} for ketones.
The method using the ionicityindex to study QSSR is successful. (1) The method is simple and accurate, and the ionicityindex is convenientto be gotten. (2) The ionicityindices character the X=0 with different chemical condition around in molecules, and realize the uniqueness token of the molecule. (3). Correlation coefficients of the models range from 0.960 to 1.000. It indicates that the ionicityindex is very useful in quantitative structure-spectrum. relationship study. (4) The good stability and strong predictive capability of these models are proved by LOO method.
We acknowledge the support from the Science and Technology Projects of Hunan Province (No.06FJ4104) and Technology Innovation Plans of Economy Commission of Hunan Province (No.[2005]283).
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