I have a few orgo and bio questions. Please let me know you guys think?
Orgo stereo questions....
- Thread starter sps27
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1. Your best bet is to look at the R-S stereochemistry of the molecule rather than eyeball it. If you look at A, the stereoisomeric carbon has S stereochemistry. The same holds true for 2 and 3.
2. You're right on that mark. E is optically inactive because carbon 1 has two of the same substituents (as you said it, they both travel the same path to Cl).
3. This one is a little tricky for me too, so don't take my on it word 100%, but even though there is a line of symmetry, the substituents of the two chiral groups can still be positioned differently with respect to one another, right? At least one of the stereoisomers will be perfectly symmetrical, thus a meso compound, but the others will have differences in their orientation. So if I'm reasoning this out correctly, it's the answer because it's 2^2 - 1 (for the meso compound). Anyone else wanna' chip in here? Haha.
4. I'd like someone to chip in here, too, but I'd imagine that the excess pyruvate would be directed towards the anaerobic pathways/fermentation. According to EK, pyruvate is reduced to ethanol or lactic acid, and will be expelled from the cell along with CO2 as a waste product. It is also through this process that NADH is oxidized back to NAD+, allowing it to be recycled for glycolysis.
Hope that helps a bit!
2. You're right on that mark. E is optically inactive because carbon 1 has two of the same substituents (as you said it, they both travel the same path to Cl).
3. This one is a little tricky for me too, so don't take my on it word 100%, but even though there is a line of symmetry, the substituents of the two chiral groups can still be positioned differently with respect to one another, right? At least one of the stereoisomers will be perfectly symmetrical, thus a meso compound, but the others will have differences in their orientation. So if I'm reasoning this out correctly, it's the answer because it's 2^2 - 1 (for the meso compound). Anyone else wanna' chip in here? Haha.
4. I'd like someone to chip in here, too, but I'd imagine that the excess pyruvate would be directed towards the anaerobic pathways/fermentation. According to EK, pyruvate is reduced to ethanol or lactic acid, and will be expelled from the cell along with CO2 as a waste product. It is also through this process that NADH is oxidized back to NAD+, allowing it to be recycled for glycolysis.
Hope that helps a bit!
