# What molecules can be eliminated in condensation polymerization?

Is there any specific rule to what kind of molecules can be eliminated in condensation polymerization? From Wikipedia I found that "small molecules" like $\ce{H2O}$ can be eliminated. Is there a more accurate criteria to what these "small moecules" are?

• AFAIK there isn't any rule. What they are depends on reaction. – Mithoron Feb 26 '17 at 14:56
• In my school exams, I often see questions asking us to determine which reactions are possible condensation polymerization, usually depending on the eliminated waste like $\ce{H2O}$ or $\ce{HCl}$. So is there at least a way I can be sure if it must be impossible, or if it must be possible? – SOFe Feb 27 '17 at 1:55
• Well, if there's no side-product in reaction then it's not polycondensation. If there is then it may be polycondensation, you should know mechanisms to be sure. BTW in polycondensation side-product (of main reaction) is produced stoichiometricly. – Mithoron Feb 27 '17 at 21:31