Organic chemistry textbook: The rhinoceros is a hybrid of a unicorn and a dragon

Analogies are tricky things. One minute, you're trying to find a clever and memorable way to illustrate molecular bonding of hydrocarbons ... the next you're suddenly Napoleon Dynamite and all your zoologist friends are yelling at you.

This image, apparently taken from a real textbook, is part of an excellent Tumblr blog of textbook fails called "Thanks, Textbooks". You should check it out.



  1. I think in the image above someone has superimposed their own drawings over top of what the book originally was showing. But I like it anyway.  =-)  …Going to check out that Tumblr! 

  2. Students enjoy a little levity in their otherwise dry textbooks.  Some authors try to inject a little humor.  But publishers seem to believe that books that aren’t 100% dry, factual content will not sell, so they typically reject any such attempts by the author.

    1.  Back in the  early 70’s I had a great introductory  college physics text where one the one the first problems was to calculate the distance to Heaven given data from Dante. Not sure they could get away with that these days…..

    1. The point is that a dragon and a unicorn don’t exist. They are supposed to be imaginary, because the chemical structures they represent are imaginary as well.

  3. I dunno.  This doesn’t seem like a text book fail to me at all–whimsical, and surprising pertinent to the issue at hand–which in context is specifically two non-existent structures used to describe one that does exist.  Wish more text books were as creative in their analogies.  

    OK, the analogy seems to be used in other places–this one is just for hybridization, but it is used to illustrate the concept of resonance contributors:

    “Imagine that you are trying to describe to a friend what a rhinoceros looks like. You might say it looks like a cross between a unicorn and a dragon. Like resonance contributors, the unicorn and dragon do not really exist. Further, like resonance contributors, they are not in equilibrium: a rhinoceros does not change back and forth between the two forms, looking like a unicorn one instant and a dragon the next. The unicorn and dragon are simply ways to describe what the actual structure- the rhinoceros- looks like. Resonance contributors, like unicorns and dragons, are imaginary, not real. only the resonance hybrid, like the rhinoceros, is real.“

  4. The point of this analogy is to show that you can have characteristics of two imaginary things represented in a real-life object. It represents two structures that don’t actually exist (the unicorn and the dragon). The real structure of the molecule (the rhino) just has characteristics of both of the imaginary structures.

    There is no good way to describe the inner workings of molecules to 19 year old college students, especially without any basis in quantum mechanics. While this analogy seems ridiculous, it does get the point across, and it has helped plenty of my students understand the weirder parts of organic chemistry.

    1. The ironic thing is that the unhybridized atomic orbitals probably have a greater claim to being “real” than the hybridized molecular orbitals, which if I am not mistaken are largely just a convenient model in certain applications.  (Wikipedia says, “this qualitative view of bonding has been largely superseded by molecular orbital theory when a more detailed analysis is required”.)

      1. The dragon picture they used looks like something from the margins of one of my 7th grade school notebooks.

  5. As it has already been stated, this is an excellent analogy for what resonance contributors really are.

    I don’t know where this specific picture is from, but Bruice has used it in her Organic Chemistry (6th ed.) with slightly different pictures.

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