I was just reading about alpha and beta linkages in certain cyclic molecules, and it said that the alpha configuration was the one in which a hydrogen was sticking out above the plane, and an OH moiety was below the plane. A beta linkage for such a molecule had the hydroxyl group upwards, and the lone H below...

But, I cannot find out how you determine which side is 'up' or 'above' and which is 'down' or 'below'...

  • $\begingroup$ See en.wikipedia.org/wiki/Skeletal_formula $\endgroup$ – Poutnik Nov 16 '20 at 21:54
  • $\begingroup$ For sugars: chemistry.stackexchange.com/questions/136694/…. For steroids: beta is above the plane of the molecule; alpha is below given the standard way of drawing steroids. $\endgroup$ – user55119 Nov 16 '20 at 23:50
  • $\begingroup$ Sugars ain’t flat. $\endgroup$ – Karsten Theis Nov 17 '20 at 4:16
  • $\begingroup$ And even if something is flat, there is still an up and down. This is anyway relevant only in relation to another objects, for instance while fusing rings etc. Nomenclature rules fixes this aspect. $\endgroup$ – Alchimista Nov 18 '20 at 8:09

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