Rules of thumb for substituting an H-atom by a group

If an H-atom in a structural group is substituted (replaced) by a group X, the numerical values of Yg and Ym do increase. Rules for the effects of these substitutions have been derived and are shown in Table 6.20. They are handy when the lists of group increments (Table 6.1 for Yg and Table 6.8 for Ym) do not contain the desired values of the substituted group, since its occurrence is rare or occasional. The accuracy of the obtained group contribution is - as a matter of course - somewhat less than listed values. 

Estimate the glass transition temperature of the polymer with the following structural unit  

The structural unit of the polymer has a molar mass of 400. It consists of the following structural groups with their corresponding group contributions  

The polymer was investigated by Briigging, Kampschulte, Schmidt and Heitz (1988) they found a Tg-value of 373/383 K and a Tm-value of 513 K and remarked that no clearing point was detectable up to 513 K the polymer started to decompose in air before the T could be reached. The agreement of Tg (exp.) and Tg (est.) is good. 

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Rigid rodcrystallisation, 706 Rod climbing effect, 526 Rod-like molecules, 252 Rod-like polymer molecules, 274 Rod-shaped particle, 276 Rubber elasticity, 401 Rubbery plateau, 400 Rudin equations, 272 Rudin-Strathdee equation, 602 Rules of thumb for substituting an H-atom by a group X, 182... 

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