TBR sterochem ? p188

[unDRdog]

Ok..WTF is the "back group" they are referring to on pg 188 of Ochem book 1 regarding a shortcut that places priority group 4 in the plane. It says: when " H (assuming its #4) is in the plane away from the back group, Take what you observe as is. :::: When "H is in the plane close to the back group, reverse what you observe"..

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[G1SG2]

Ok..WTF is the "back group" they are referring to on pg 188 of Ochem book 1 regarding a shortcut that places priority group 4 in the plane. It says: when " H (assuming its #4) is in the plane away from the back group, Take what you observe as is. :::: When "H is in the plane close to the back group, reverse what you observe"..

I don't have the book, but I'm guessing what they mean is that if H or the lowest priority group is not pushed away from you or is pointing toward you, just assign priorities like you always do, but reverse the configuration. Like if you ended up with S, it's really R because H was pointing toward you and it should've been away from you, and vice versa. Or, they could be talking about the H pointing straight up or into the plane of the page, in which you would rotate the molecule and switch the H with the group pointing away from you. So H would end up away from you, and that other group would now be pointing into the plane of the page.

 

[Seraph 84]

Pretty sure the back group is just the methyl group - the group with the hash-wedge marks.