Dec 13, 2013
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  1. Pre-Medical
A passage that I read indicated if a compound was diluted to half its concentration than its optical activity would decrease as well. I want to cross check this with those that are efficient Organic Chemistry. If I decrease the concentration of a compound does the optical activity decrease from a positive rotation to a negative rotation?


Senior Member
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7+ Year Member
Oct 30, 2004
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The most you can decrease the concentration down to is 0, and when there is nothing, optical activity approaches zero as well.

So a complete sign reversal of optical activity is not possible when you're dealing with just one optically active species. The most you can change to is no activity at all.


5+ Year Member
May 29, 2012
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  1. Pre-Medical
A= Ecl
A = absorbance
E = Molar absorbtivity (specific for a compound)
c = concentration of substance
l = length of the container

No, a substance that has positive rotation will experience a decrease in rotation and a decrease in concentration simultaneously until it reaches a rotation and concentration of 0. Light passing through solution containing its enantiomer, on the other hand, will experience an increase in rotation with a decrease in concentration until it too reaches 0.
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