Gauche or Anti?!
Started by PooyaH
That's my understanding too. But there's a problem in Destroyer Odyssey that has the Newman structure of a 1,2 ethanediol and says that normally it would be the anti but in this case it is the gauche that is the most stable! Maybe it's just this particular example in which I don't know the reason why.
Correct - in that question the gauche was more stable because INTRAmolecular H bonding occuring between the alcohol groups.
I hope there are not questions like that on the DAT because it seems like such a judgement call. I have not read any text that even teaches to look for intramolecular h bonding when evaluating stability of ecliped, anti, or gauche.
I mean really... how can we qualitatively know that.
Steric hinderence + H bonding = less energy than zero steric hinderence? lol.
I hope there are not questions like that on the DAT because it seems like such a judgement call. I have not read any text that even teaches to look for intramolecular h bonding when evaluating stability of ecliped, anti, or gauche.
I mean really... how can we qualitatively know that.
Steric hinderence + H bonding = less energy than zero steric hinderence? lol.
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Uhuh, yeah in that case it makes sense. Thanks.
I think it's because methyl has 4 atoms whereas a hydroxyl group only has 2.
O isn't larger than C. Going to the right of peroidic table means the atom gets smaller.
Just did random google search to try to find a rule in finding steric strain. Couldn't really find a rule. But this is from www.people.vcu.edu/~s2cmring/Chapter 3.doc
These are for a ring, but the rule is pretty much the same; you want the largest group furthest apart.
"If the ring is substituted, you want to get the largest substituent in the equatorial position. This minimizes steric strain. The largest substituent is not defined by molecular weight but by physical size
Ex. CH3 is bigger than Br, even though it weighs less"
I remember chad mentioning in his video that CH3 is bigger than Br/Cl/OH.
Also here's his response to Br vs CH3 in a ring.
"The methyl group it turns out does indeed have the priority here and should get to be equatorial before the Br. There's no intuitive way to know this; it's just something we determined empirically and now you have to remember it."
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