SN2 vs SN1 rxns – Stories of Eternal Love & Conflict

Guest post by:  Rami Ibo

On the occasion of the 2011 International Year of Chemistry, the Physical and Biophysical Chemistry Division (I) of IUPAC announced a Student Chemistry Cartoon Competition. The goal of the competition was to illustrate a chemistry principle in a manner that can enrich the teaching of chemistry ( So I decided to participate in this event and I drew by hand a chemistry cartoon which I called: SN2 vs SN1 rxns – Stories of Eternal Love & Conflict. 🙂

I sent in the cartoon along with the description that they asked for.  Unfortunately, I did not win 🙁 (tears in my eyes and tissue box next to me :P)… However, I would still like to share it with you here on Sandpaw since I think the idea of teaching chemistry (or any science for that matter) in an accessible/humorous way is relevant to the discipline of Science Communication.

Here is the description of the cartoon. I hope you find it as informative and enjoyable as I did!

How does the cartoon relate to a chemistry principle?

It teaches in a simple and humorous way, the difference between SN2 (Substitution, Nucleophilic, Bimolecular) and SN1 (Substitution, Nucleophlic, Unimolecular) reactions in organic chemistry. I hope students will be able to relate to the cartoon and be able to notice the key features that distinguish between an SN2 reaction and an SN1 reaction.

Summary of the cartoon:

 The cartoon is drawn on an A4 page and is split into two halves: the first half deals with SN2 reaction while the second half deals with the SN1 reaction. In the SN2 story, I introduce the main character of that story: CH3Cl in which the carbon is annoyed by the electronegative chlorine and how it withdraws all the electron density towards it [the chlorine]. Then I introduced the second character, OH, which comes into the scene lonely and floating by. As soon as the carbon in CH3Cl and OHsee one another, they fall in love (much to chlorine’s dislike). As the bond between the OH and the carbon forms, the bond between the carbon and chlorine starts to break (which is the key feature of SN2 reactions – it is a concerted mechanism where bond making and bond breaking happens at the same time). Chlorine leaves the molecule and becomes a chloride ion (which happens to be a very good leaving group as it can easily accommodate the extra negative charge).

 In the SN1 story, OH‘s twin brother (who unsurprisingly happens to be another OH ion) meets CH3Cl’s older sister CR3Cl. Again, the OH and the carbon in CR3Cl fall in love. However, it is not possible to form a bond between the OHand the carbon of CR3Cl due to the bulkiness of the R (alkyl) groups (in other words, steric hindrance about the carbon prevents and SN2 reaction from taking place). This makes the couple sad. But in no time, the carbon in CR3Cl gets an idea! It figures out that in order to bond with OH, it would need to break a bond first to create a vacancy (an SN1 reaction!). And in a very menacing move, the carbon “kicks out” the much disliked chlorine (in the form of a good leaving) from the molecule and becomes [the carbon] formally positively charged (a carbocation). And now, the OH and the carbocation are able to form a bond and live happily ever after!

Rami Ibo

Note: For those who would like to use the cartoon, feel free to do so but please credit my name. Thank you.

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2 Responses to SN2 vs SN1 rxns – Stories of Eternal Love & Conflict

  1. jenny says:

    Wow what a cartoon !!
    You have just explained love in the language of chemistry…!!
    I have never seen anything like this before… even in my love blog How to make a guy fall in love with you can’t explain like this….
    Worth reading your blog… Really nice one…
    I will share this on my site and will give credit of course….

  2. Rami Ibo says:

    Hi Jenny!

    Thanks for you comment! (little screams in my head since someone commented! :P). When I read “You have just explained love in the language of chemistry…!!” I thought: Did I? My intention was to explain chemistry in the language of love… After reading what you said, you actually made me look at my own cartoon in a different way… As much as this is a chemistry mini-lesson explained in terms of love, it is also a love story explained in chemistry terms. Glad you enjoyed it and thanks for crediting it on your site Jenny.

    Rami 😀

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