Dat Destroyer Q 85 orgo

[jd399]

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can u please explain why u switch things around when going from newman into a fisher?😀

 

[nze82]

can u please explain why u switch things around when going from newman into a fisher?😀

This is a hard question to answer, because it requires lots of visualization. But to give a short answer, it's mainly due to the fact that Fischer projections represent the molecule in the plane of the page, while Newmann projections represent the molecule in 3D. So, you need to move certain groups around, in order to maintain the proper orientation as you convert from Fischer to Newmann projection.

 

[pbure9]

Basically the trick here according to destroyer is that you keep the orientation of everything on the front carbon the same and for the back carbon you reverse it (just switch it around).

The reason why this works (and you can use a model kit to see), is if you rotate the back piece of the newman (the one "in" the page), the CH3's match up as in the case in number 85, and the H is now on the left side with the Cl on the right side.

 

[GiTsticker]

Haha, let me try to explain. So in the fischer projections, everything that is vertical is going into the page, away from you. Everything on the sides are coming out of the page, toward you. Also, the main carbon backbone is vertical. Now on the newman projection you are looking from the top of the molucule, down the backbone. If any part of the main carbon backbone is facing anywhere but up, that part must be rotated so that it IS facing up. That way when you rotate the molecule to look at it from the front (fischer) all of your carbons that comprise the backbone are vertical (once again, into the page) and the correct stereochemistry is preserved.