4. Conclusions and outlook

In this chapter, we reported the extension of our empirical relationship established in 2011 for the computation of zero-point vibrational energies (ZPE) of organosilicon compounds. The bond contributions of Si—H, Si—C, Si—Cl, Si—O, and Si—Si were determined. The application of the proposed empirical model to more than 90 organosilicon shows the reliability of this model. The results derived from this model are compared with those obtained by quantum chemistry methods (semiempirical (AM1) and DFT (B3LYP/6-31G\* )) on the one hand and to those obtained by similar empirical approach on the other hand. As a result, the empirical

the average error decreases from 2.5 to 1.37 kcal/mol for AM1 and from 1.08 to 1.00

organosilicon compounds (our empirical model, Schulman-Disch extended empirical formula, AM1, and DFT) are correct. But the empirical approaches have the advantage of simplicity and speed. In addition, the approach based on bond contributions additivity has also the advantage of providing different values of ZPE for

As a result, the four estimates of vibrational zero-point energy of the

Correlation between experimental ZPEs and empirical values calculated using Eq. (5).

Modern Spectroscopic Techniques and Applications

Calculation method Linear model

Proposed empirical model (Eq. (5)) 0.993 � 0.002 0.9998 0.99 0.272 0.9994 AM1 1.025 � 0.003 0.9992 0.95 2.212 0.9982

Schulman-Disch extended model (Eq. (4)) 0.984 � 0.0038 0.9986 0.95 3.545 0.9972

Atom Increment Ref. Atom Increment Ref. H 7120 [25] Cl 2220 [26] C 3880 [25] S 1870 [27] N 4050 [26] Br 1600 [27] O 3400 [26] Si �3510 [28] F 3270 [26] P 0.035 [29]

Coefficients a, b, and R<sup>2</sup> in equations ZPEexp = b + aZPEtheor in both cases b = 0 and b 6¼ 0.

) 0.999 � 0.002 0.9996 0.95 0.304 0.9986

ZPEexp = aZPEtheor ZPEexp = b + aZPEtheor a R<sup>2</sup> ab R2

for DFT(B3LYP/6-31G\*

Atom contributions to ZPE (in kcal/mol).

DFT (B3LYP/6-31G\*

Figure 2.

Table 3.

Table 4.

48

).

model provides a simple, fast, and accurate way to estimate the vibrational zeropoint energies of organosilicon compounds.

References

389-397

12904-12910

1986;41:319-332

1990. p. 131

267-279

8925-8932

51

the Effects of Pesticides on Human Health, Vol. 18.

[1] Grice ME, Politzer P. Use of molecular stoichiometry to estimate vibrational-energy. Chemical Physics

[2] Irikura KK. Experimental vibrational

DOI: http://dx.doi.org/10.5772/intechopen.87021

Vibrational Zero-Point Energy of Organosilicon Compounds

[9] Sidell FR. Soman and sarin: Clinical manifestations and treatment of

organophosphates. Clinical Toxicology.

[10] Smeyers YG, Villa M. Influence of the vibrational zero-point energy correction on the amine inversion barrier and the far-infrared spectrum of methylamine. Chemical Physics Letters.

[11] Sana M, Leroy G, Peeters D, Wilante C. The theoretical study of the heats of formation of organic compounds containing the substituents CH3, CF3, NH2, NF2, NO2, OH and F. Journal of Molecular Structure (THEOCHEM).

[12] Dykstra CE, Shuler K, Young RA, Bai Z. Anharmonicity effects on zero point energies of weakly bound

molecular clusters. Journal of Molecular Structure (THEOCHEM). 2002;591:

[13] Fliszar S, Poliquin F, Badilescu I, Vauthier E. Structure dependent regularities of zero-point plus heat content energies in organic molecules. Canadian Journal of Chemistry. 1988;

[14] Tajti A, Szalay PG, Császár AG, Kállay M, Gauss J, Valeev EF, et al. HEAT: High accuracy extrapolated ab initio thermochemistry. The Journal of Chemical Physics. 2004;121:11599-11613

[15] Zahedi-Tabrizi M, Tayyari F, Moosavi-Tekyeh Z, Jalali A, Tayyari SF. Structure and vibrational assignment of the enol form of 1,1,1-trifluoro-2,4 pentanedione. Spectrochimica Acta A.

[16] Merrick JP, Moran D, Radom L. An evaluation of harmonic vibrational frequency scale factors. The Journal of

accidental poisoning by

1974;7:1-17

2000;324:273-278

1988;164:249-274

11-18

66:300-303

2006;65:387-396

[3] Pilcher G. In: Hartley FR, editor. The Chemistry of Organophosphorus Compounds, Vol. 1. New York: John

Guillemin JC. Synthesis and microwave spectrum of (2-chloroethyl)phosphine (ClCH2CH2PH2). The Journal of Physical Chemistry. A. 2009;113:

[5] Durham HD, Ecobichon DJ. An assessment of the neurotoxic potential of fenitrothion in the hen. Toxicology.

[6] Ecobichon DJ, Davies JE, Doull J, Ehrich M, Joy R, McMillan D, et al. In: Baker SR, Wilkinson CF, editors. Neurotoxic Effects of Pesticides, in

Princeton, NJ: Princeton Scientific;

VG. Computational study of the thermodynamic properties of organophosphorus(V)

compounds. Journal of Molecular Structure (THEOCHEM). 2007;811:

[8] Dorofeeva OV, Moiseeva NF. Computational study of the

thermochemistry of organophosphorus (III) compounds. The Journal of Physical Chemistry. A. 2006;110:

[7] Dorofeeva OV, Ryzhova ON, Zverev

Letters. 1995;244:295-298

zero-point energies: Diatomic molecules. Journal of Physical and Chemical Reference Data. 2007;36:

Wiley & Sons; 1990. p. 127

[4] Mollendal H, Konovalov A,

Establishing these empirical rules is becoming increasingly important. Indeed, thermodynamic data play an important role in the understanding and design of chemical processes. Experimental methods require appropriate equipment, sufficient product purity, time, and cost of experience. The use of such techniques becomes difficult for toxic compounds. In addition, the large difference between the number of synthesized compounds and the available experimental data continues to increase. In such situation, the practical approach is to use predictive models to estimate the properties of compounds from the molecular structures. In this outlook, we propose to extend the field of application of the proposed empirical model to other compounds such as organoborons, organomagnesians, etc., and to establish similar approaches to estimate other thermodynamic quantities such as enthalpy of formation (ΔH0 f), entropy (S0 ), and heat capacity (C).
