AG22 Posted May 7, 2009 Report Share Posted May 7, 2009 Hey guys, I think this might be an error, or a more likely explanation is that I am mistaken The question states: When described using rectus or sinister, the spatial arrangement of substituents around a chiral atom is called: A- achirality B-absolute configuration C-observed roation D- enantiomeric purity. I chose...C, but the answer is B. What do you all make of this? Muchas gracias! Link to comment Share on other sites More sharing options...
ontariostudent Posted May 7, 2009 Report Share Posted May 7, 2009 R and S have nothing to do with rotation- they tell you about the spatial arrangement of the different atoms within a molecule, that is its absolute configuration. Absolute configuration doesn't change with molecule rotation because it has to do with the physical bonds of the molecule that hold the atoms in one absolute way. Link to comment Share on other sites More sharing options...
Jochi1543 Posted May 7, 2009 Report Share Posted May 7, 2009 ...*shudder* Link to comment Share on other sites More sharing options...
AG22 Posted May 7, 2009 Author Report Share Posted May 7, 2009 R and S have nothing to do with rotation- they tell you about the spatial arrangement of the different atoms within a molecule, that is its absolute configuration. Absolute configuration doesn't change with molecule rotation because it has to do with the physical bonds of the molecule that hold the atoms in one absolute way. So, the answer is C yeah? Link to comment Share on other sites More sharing options...
ontariostudent Posted May 7, 2009 Report Share Posted May 7, 2009 So, the answer is C yeah? No... it's B, absolute configuration. Observed rotation cannot be determined from R vs S, which describes the spatial arrangement of the atoms. Observed rotation is just a property that describes the way plane polarized light is rotated by the molecule. It's like boiling point or melting points- something that has to be measured. EDIT: What I described as "observed rotation" is actually optical rotation. Observed rotation might be something else but I've never heard of it, it's definitely not the answer! Link to comment Share on other sites More sharing options...
AG22 Posted May 7, 2009 Author Report Share Posted May 7, 2009 No... it's B, absolute configuration. Observed rotation cannot be determined from R vs S, which describes the spatial arrangement of the atoms. Observed rotation is just a property that describes the way plane polarized light is rotated by the molecule. It's like boiling point or melting points- something that has to be measured. EDIT: What I described as "observed rotation" is actually optical rotation. Observed rotation might be something else but I've never heard of it, it's definitely not the answer! OHH I'm such a fool I confused R and S with L and D. WOW. I was like..."rectus and sinister??" Thanks! EDIT: Yeah...I feel like an airhead Link to comment Share on other sites More sharing options...
Octavius Posted May 8, 2009 Report Share Posted May 8, 2009 Definitely B. Link to comment Share on other sites More sharing options...
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