# 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

## 2 Answers

As an abstract answer, to me it would be whatever is commercially viable to manufacture and sell. Commercial polymerisation processes eliminate ethylene glycol (in the manufacture of PET) which is probably recycled, methanol in transesterification reactions, ethene or propene in metathesis type, phenol (recycled) in the use of diphenylcarbonate with bisphenol A, etc. In home applications, acetoxysilicone sealant gives off acetic acid. So, anecdotally, it seems "simple" molecules of MW around 100 or less might meet your criteria.

• MW refers to relative molecular mass? – SOFe Feb 28 '17 at 11:24
• Yes, I was being a bit lazy – Beerhunter Feb 28 '17 at 17:25

yes , only small molecules such as H2O or CO are eliminated , as such it is no rule . if large and bulky molecules are extracted as waste, it will no longer be called an elimination product but a side-product. i hope you understand now !