How do you draw your benzene rings?
No, not how do they look when you’re finished, but what are the motions you go through when you put pen to paper? And I do mean pen to paper, obviously drawing benzene rings with your favourite chemistry-drawing software is done with a simple click of a button.
I started thinking about this when I saw this comment on one of @Chemjobber‘s posts — one in which Carmen Drahl gets a shout out for including hand-drawn chemical structures in some of her posts over at CENtral Science. This, in turn, led to a call by Carmen for readers to send in pictures of structures drawn by their own fair hands — the gallery can be found here.
So, benzene. When you first put pen to a blank piece of paper, you have a number of choices to make. Do you draw the hexagon so that its top and bottom are parallel to the top of the piece of paper, or so that the left and right sides are parallel to the left-hand side of the piece of paper? Or put more simply, is your hexagon sitting on a single point, or is it resting comfortably on one of its sides? Of course, if the benzene ring is part of a larger structure, you might be forced to choose one orientation over another. But if you’re just drawing a single solitary benzene ring, or if you’re not constrained in any way by the bigger picture, do you always start by drawing your benzene ring the same way up?
Orientation aside, once you’ve made that decision, which way do you move the pen? Do you always follow the same sequence of strokes? Do you lift the pen from the paper before completing the hexagon and going on to the double bonds? After giving it some thought, I’m pretty sure I always draw my benzene rings the same way — and if you’d asked me to describe how I did it without actually going through the motion, I’m not sure I would have got the answer right. I guess it’s because it’s second nature; I’ve done it so many times it just happens, and the way I do it is tucked away in my subconscious somewhere. So, for me, I always sit my benzene rings on a point (if I have a choice) and I lift my pen off the paper twice before even completing the hexagon. And I’m pretty sure I always draw the double bonds in the same order and direction as well. Full gory details shown in the picture.
Just as Chemjobber suggests that a chemist’s hand-drawn structures are a signature of sorts and Carmen agrees that they carry an echo of personality — I think the way in which we actually draw the structures probably varies quite a bit from person to person as well (what it says about an individual, however, heaven only knows!). There are hundreds of ways you could actually draw the nine different lines that make up a benzene ring (probably only a handful of sensible ones though) — but just imagine the permutations for something like Taxol! And yes, benzene has nine lines, anyone out there drawing a hexagon with a circle in the middle just needs to stop.
I realise this is all a bit silly, but it did get me thinking about drawing structures. So, how do you draw yours?!
Lionel Hart used to draw them pretty much rectangular … and to the frustration of many would start a reaction scheme on the board .. then go UP (queue everyone in the room screwing up their piece of paper and starting again) … then he’d go LEFT (queue everyone once more binning their notes and starting AGAIN).
Of course no-one ever complained because we’d all shared this moment http://www.guardian.co.uk/education/2001/may/16/universityguide.emilywilson … just like the thousands before us did and the hundreds would afterwards :p
Using your numbering, I draw the first hexagon the same way: A vertical bond first, then three more without the pen leaving the page (so the only carbon missing is 5), then finish the hexagon without the pen leaving the page. But then I add double bonds in the reverse order to you.
It took a while, and the back of an Org. Lett printout to figure out how I do this…it is second nature now and I rarely think about it. I wonder if the way I draw this is a right handed thing? No bond is drawn with the pen moving right to left. Any lefties out there who can clarify?
And I just started thinking about what I do when I need a ring drawn at 90 degrees to that – Then I draw the ring as two halves three bonds each, and again moving from left to right all the time.
I do mine completely differently. For the hexagon I do 1->6 then 3->4 then 1->2->3 then 6->5->4. Then for the double bonds 2->3, 4->5, 1->6. Interesting!
Almost exactly the same way! Except…the last double bond, I draw 4->5.
Never thought about this before … like you say you have to draw it out to work out if you have a way and what it is.
I draw my hexagon very consistently in two halves 1 -> 6, 1->2, 2->3, 6->5, 5->4, 3->4
shamefully there appears to be some inconsistency in the way I add in the double bonds afterwards … wonder if this is anything to do with the fact that most of the time I draw by hand it’s for teaching and I’m getting kids doing resonance structures etc.
Perhaps I am a psychopath…I double back over one of the bonds in the ring:
2→1→2→3, lift, 1→6→5→4, lift, 3→4
and the center is made as a counterclockwise circle drawn starting just under carbon 2
That’s just weird.
Thankfully I drew a benzene ring during class today. So, I got to do it naturally and only thought about it afterwards …
1 to 6. Lift. 1 to 2 to 3 to 4 to 5. Lift. 5 to 6. The double bonds go in any order and can be dependent upon any substituents on the benzene ring.
I’m almost exactly the same as Stu – for the hexagon I go 1 – 6, but followed by 1-2-3-4-5-6. My double bonds are almost the same, 1-6, 2-3, but 4-5. I’m convinced I’ve followed my Ph.D. Advisor on this – even though it’s been years, I can still visualize him drawing out aromatic rings (and with a total synthesis project, there were just a few to draw ;) ).
Hmm one more way, that’s natural for me: 1>6>5 up 1>2>3>4>5 and double bonds: 1>2 6>5 3>4 (yeah, I always draw another resonance structure)
I am a little shocked to learn that everybody here seems to draw the double bonds. Are you serious? Circle in the middle for me. That is, if I draw a benzene at all. Most of the time, a Ph or a φ.
I do not think it matters. Each to his own as long as it is clear. All we are doing is expressing our microscopic view by a drawing, and no matter what we draw it will be wrong. First thing is every benzene molecule, indeed every single molecule, is indistinguishable from others with identical structure. Nature does not put numbers on atoms, we do. I also would always draw a ring and never double bonds, unless in a larger structure where it matters. If you draw all your permutations, you will get the equivalence to a ring. So I think not drawing a ring is misleading and ignores resonance.
I do like the line: ‘Nature does not put numbers on atoms, we do’ – very true! As for rings – I disagree, I think drawing the ring actually hides what is really going on. Take naphthalene – do you draw two rings? That might imply 12 pi electrons to some observers, but we all know that there are only 10. And what about triphenylene – do you draw a ring in the middle or not? Drawing the pi bonds (rather than rings) actually enables you to delve deeper into resonance, especially where different resonance contributors are of different energies.
I first considered pimping my original post with something about how a circle is closer to nature, but honestly – that is neither my reason nor excuse. For me, it boils down to sheer laziness. Even worse, I am fairly inconsistent too; I would never pick the ring variation of benzene in ChemDraw and I always draw double bonds for heterocycles such as thiophenes and pyrroles. Pyridines… double bonds about 80% of the time.
Ring in the middle of a triphenylene – food for thought, but of course outright wrong!
Question: Is the ring in the middle concept acceptable for aromatic compounds only? I have never, ever seen cyclooctatetraene depicted with a ring in the middle – but would it be absolutely wrong? (Probably yes, I guess, because nature does what it can to avoid antiaromaticity and twists the ring out of the plane, and a circle would imply flatness. Or what do you say?) While still on the topic, you never encounter ferrocene depicted with double bonds, do you?
Yep, if you insist on drawing a ring, it has to be for aromatic (or antiaromatic) systems. And yep, for cyclooctatetraene it would be absolutely wrong – that molecule has a bucket shape, nowhere near flat. Good point about ferrocene – I guess if you don’t draw rings you need to put a negative charge on each Cp ring and then +2 on the Fe… and that just looks a bit messy.
So drawing a ring for cyclobutadiene (flat, antiaromatic, very unhappy even to exist) would be OK? Never seen it.
Me neither, but if it’s OK to draw a ring for an aromatic system, why not an antiaromatic one? Just an alternating system of pi-sigma-pi-sigma-etc in a ring – just happens to have 4n rather than 4n+2 electrons… But anyway, as I said, I would generally avoid drawing rings at all!
This caused quite a discussion in our research group… I draw mine exactly the same as you except for the last double bond which I draw from 4 -> 5! There must be some sort of Freudian psychology behind this!