There might be programs for this, but if the attachments are electron withdrawing, the the epoxy group is more reactive. If the attachment is bulky ie non branched vs branched aliphatic, then yes you can predict. Also for aryl or cyclohexyl, these are bulky and branched, so the epoxy group would react slower. It also depends if the group is directly attached to the epoxy, or just close by, ie one carbon away, for example. If the aryl group has electon withdrawing groups and is attached to the epoxy group, then spending where the epoxy group is, meta, para, ortho, will affect the reactivity. Like was for electron donating groups to the aryl ring.

I am not an expert in terms of doing Chemsitry via computer programs, but I am sure someone can comment on this. I know they must have them. There are known reactivities based on the periodic table, ie F>I>cloro for electron withdrawing effects.

So I use the eyeball method, but if you do not have organic chemistry classes under your belt, I suggest getting a computer program tha does it for you.

Sorry for the typos. Spellcheck constantly changes my words and I forget to check spellcheck.

Of course, it IS affected, this is the main story of the organic chemistry, otherwise most of the reactions has been known for decades. The reactivity depends on the electron density distribution (which in turn is determined by inductive, mesomeric, and other effects of the rest of the molecule) as well as by steric factors. All these may be additionally altered by the solvent type (ionization, association, etc).

I believe epoxy reactivity is a well known issue, described in the literature in detail (depends, of course, on the reaction you are interested in).

To predict the reactivity of a given functional group along different molecules, one of the most important points is knowing which kind of reactions this group commonly suffers, as well as knowing the respective mechanisms. So, in the case of epoxy groups, I suggest that you specify the reaction that you are taking into consideration, and then understand its mechanism, so you will have better conditions to predict more accurately the reactivity of such epoxy groups in aromatic, bulky or alifatic compounds.

Many thanks for the comments!

What I am particularly looking for is corroboration of my hypothesis that the cationic ring-opening polymerization of epoxy compounds proceeds faster in case of aliphatic attachments, compared to molecules with aromatic rings (such as SU-8).

The argumentation of slower reaction in case of bulky and branched system supports this proposition. Does this count among basic knowledge or are there any suggestions for a reference?

I would say this is reasonable. Cationic ring-open polymerization proceeds via attack of the macrocation on the epoxy ring; in the case of aromatic group attached to macrocation its charge will be highly delocalized, and this this cation will be less reactive than that without delocalization. In other words, I would recommend to compare the reactivities of respective cations, not epoxy monomers. I guess, some common examples may be found in classical textbooks on polymerization (Odian?) as well as in organic chemistry textbooks (Carey?). You could probably project those examples onto your particular reactants.

That cannot be taken as a rule. Sn2 opening of an epoxide ring attached directly to an aromatic nucleus, for example, is very fast - just like benzyl chloride reacts fast in Sn2 type reactions. That's explained in every modern OrgChem textbook.

But on the other hand SU8 also looks like an excellent electrophile (for another reasons though - look up Neighbouring group participation).

It would be a tough call to predict if styrene oxide reacts faster than Su8, for example.

I am not an expert in organic chemistry, so I will not argue against your example, of course. Just once again to mention the fact that we do not have to compare reactivities of different epoxies in reaction with the same cation - right the opposite, with different epoxies the cations will also be different. As far as I remember, in radical polymerization the general rule is as follows - more reactive is a vinyl monomer, less reactive is the corresponding radical. This leads to various considerations in copolymerization of monomers mixtures, units distributions, etc. I think, in the discussed case we should also bear in mind that in polymerization of epoxies the change of epoxy monomer reactivity may also alter the corresponding cation reactivity...

Yes, and the effect is huge. There are mainly two effects: electronic stabilisation of intermediates and steric hindrance .

This is very helpful. Thanks a lot!