# How can you calculate ring strain in beta lactams for different penicillin drugs?

I am currently working on a lab, where I am trying to calculate whether the R group in penicillin type drugs has an affect on the ring strain of the beta lactam. I know how to find ring strain in cycloalkanes through the molar heat of combustion, however I can't find any information about the combustion of beta lactams as I'm sure it doesn't happen often, so is there another way I can calculate the ring strain of the beta lactams in different penicillin type drugs?

Thanks,

• Are you looking for an experiment to confirm the ring strain or is a computer model also an option? Mar 24 at 12:29
• I cannot currently do an experiment in a lab so I am looking for a way to calculate ring strain with data available online. Computer modelling is definitely an option. I have also tried using Webmo to calculate the ring strain, however the strain energy calculations were completely different each time even if I was using the exact same penicillin drug. Mar 24 at 12:58
• Would be the heat of formation instead / in addition to the heat of combustion you an alternative suitable for you? This then wider scope may increase the likelihood to identify literature. A first entry found was «AM1 study of the electronic structure of benzylpenicillin» by Venugopal et al. in IJOBC here, e.g. about the influence to protonate the lactam-N. Mar 24 at 13:23

As an example you can look at cyclopentene.If it is opened during Metathesis and you saturate the doublebonds at the end of the chain with two $$\ce{CH2}$$ or one ethene molecule.