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Empirical Schemes of Vinyl Monomers' Relative Reactivity in Radical Addition Reactions

Variant II

Another way of utilizing Eq. (3) is the using its polar part as a theoretical index of reactivity. So, we are going to tabulate electronegativities and energy gaps of monomers and use them as parameters of activity for correlation purposes. This time only linear (M_j) parameters of monomers shall be obtained through optimization. The working equation of such a scheme be

(eq. 5)

The set of optimized parameters M_j is presented in Table XI. Parameters N and G where obtained by PMO method (see previous chapter). The quality of prediction of this scheme is a bit lower than that of the previous one (mean deviation of calculated rate constants is approximately 60%). But, it has the considerable advantage of being "semiempirical" because the number of empirical parameters is essentially reduced and an important part of predictions is based on values calculated by quantum chemistry method, N и G. Therefore, the scheme can be called the "Scheme of electronegativities for the reactivity of vinyl monomers".

Table XI. Parameters of the Scheme of electronegativities¹⁾, Eq. (5). Const = 80 (optimized value).

Monomer	M	N	G	Radical	N
St	0.00	1.37	13.0	CH₃^•	1.26
MSt	−0.45	1.19	12.8	c-C₆H₁₁^•	2.75
AN	0.78	−1.74	14.1	5-C₆H₉^•	3.42
MAN	1.05	−1.69	13.8	t-Bu^•	2.52
MA	0.76	−2.19	14.4	t-BuO^•	−2.71
MMA	1.39	−2.08	14.0	t-BuOO^•	−2.74
VA	−4.42	2.01	13.3	PhC(CH₃)₂OO^•	−2.36
IPA	−5.50	2.00	13.0	Cl-PhS^•	−2.73
Eth	−2.04	1.30	14.1	CF₃^•	−4.00
VBuE	−6.34	3.19	13.2	CCl₃^•	−0.70
VCl	−0.73	−0.36	14.1	poly-IPA	−0.76
VCl2	0.55	−1.63	14.0	poly-VA	−0.82
2ViPy	0.80	0.79	13.3	poly-MMA	−1.03
4ViPy	0.87	0.13	13.4	poly-MA	−0.52
MVK	0.86	−1.46	14.2	poly-MAN	−1.43
1,1-DPE	2.86	0.80	13.6	poly-AN	−2.09
VF	−3.28	1.00	13.7	poly-MSt	2.73
				poly-St	1.86

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¹⁾

Parameters N/G of monomers were calculated relatively HOO^•. Parameters N of radicals were obtained by optimization procedure, while G of different reaction series were supposed to be equal