Drawing hydrogens

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Dbhaskar
Posts: 8
Joined: Fri Sep 20, 2013 3:00 am

Drawing hydrogens

Postby Dbhaskar » Fri Mar 14, 2014 11:10 pm

I noticed that for ring flips (cyclohexane) within the practice finals, hydrogens are not drawn. However, when asked to draw the chair structure generally hydrogens were included in the drawing. Should we just draw the substituents, or is it okay to show the hydrogens all the time?

104277942
Posts: 161
Joined: Fri Sep 20, 2013 3:00 am

Re: Drawing hydrogens

Postby 104277942 » Sat Mar 15, 2014 12:54 am

I'm actually confused about that too. But if I heard correctly, during Matt's review session Friday night he said if cyclohexane has substituents, you only need to draw the substituents and their respective positions on the chair conformation and then on the ring flip of the chair conformation. The hydrogens are already implied I think. Like with a regular cycloalkane drawing, you do not draw all the hydrogens on the carbons because they are implied.

If my thought process is wrong, someone please clarify!

y3chem
Posts: 174
Joined: Fri Sep 20, 2013 3:00 am

Re: Drawing hydrogens

Postby y3chem » Sat Mar 15, 2014 3:12 am

generally we only draw substituents for ring flips because it is easier to show that the substituents's position changed from axial to equatorial or equatorial to axial (which is what ring flips does). By putting in H atoms, it makes the change in position harder to see, that's why we don't put in H atoms during ring flips (generally) .

However, when you are drawing conformations, we put in all the atoms because we don't need to emphasize a certain change in position. By putting in all the atoms, we show that we know how the atoms are position in each conformations. :)--> although in reality, the hydrogen atoms are usually implied in the graphs, and no one really draw them out.

Hope this helps


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