Enantiomer / Diastereomer Chemical and Physical Properties

[[sammich]]

Alright so I know the common answer:
Enantiomers - same chemical and physical properties
Diastereomers - different chemical and physical properties

In lecture, our professor said that enantiomers can have different biological effects. I was confused because, as he had said earlier, they have the same chemical properties. I did some research into it and found that enantiomers react differently with chiral molecules. Therefore because there is an exception to the rule, by definition of chemical property, enantiomers do not always have the same chemical properties.

That was 3 weeks ago.

Today we had an exam, and unexpectedly, there were 2 T/F questions exactly as follows:

___ Enantiomers have the same chemical and physical properties

___ Diastereomers have the same chemical and physical properties

I didn't even think about it and marked FALSE for both. Now I'm sitting here kicking myself because I know my professor is going to mark the first question wrong. I'm trying to get all my facts straight so when I get the test back, I can explain my reasoning to him, and that his question did not specify if the enantiomers were in achiral environments.

My logic is as below: (Sorry, could only think of it using discrete math notation: upsidedown A means "for all", backwards E means "there exists")

http://i54.tinypic.com/2450fuw.jpg

If I wasn't rushing to finish the exam in time, I would've been more thorough and remembered that there was a discrepancy between the lecture and what I had found, and I would have asked him to clarify the question. He's a very educated guy, and very approachable, so I will be able to explain my reasoning. But... before I make a fool of myself, I just want to make sure that I am not mistaken

So... Am I misinterpreting something?

Thanks in advance!



[Oh, and I also read that enantiomers can have different smells and tastes... Are those not physical properties? Then why is our textbook, like many online sources, saying they have identical physical properties?]
EDIT: nevermind the smell/taste question, that just brings me back to the original question because smell and taste are interactions with our bodies, which contain chiral compounds

[varialectio]

You are essentially correct as the tragic story of Thalidomide illustrated. That statement of enantioners having the same chemical and physical properties ought to be qualified by "except in their interaction with other asymetric systems"

In addition to interactions with chiral biological systems, one way of illustrating the difference in physical properties is the results of a chiral gas chromatographic separation. With a second chiral molecule as the stationary phase, typically a cyclodextrin, the retention time of the two enantiomers is slightly different, enough to effect a separation. Ergo the physical interactions of the two enantiomers with the stationary phase are not equal.

[Nemus]

And in a strong magnetic field with an electric field at right angles, you'd expect different diffusion rates, boiling points etc.
Your professor is propagating a myth, although a fairly useful one under normal circumstances.

[[sammich]]

Follow up:

Got the exam back friday, and as expected, the question was marked wrong. After he has us come pick up the exams, he hangs around the front of the room in case we have questions. I approached him, and he said that my answer was incorrect. I said, "I thought enantiomers react with chiral molecules differently, that's why they have the different biological effects."

He paused for a second, and responded, "That's something that's more in the Biological Chemistry department, for our class we're talking about achiral environments."

I asked, "But technically I am correct, right?"

He said yes.

After most of the students had left, I was walking out of the door and the professor was directly behind me. When we were outside, he says, "Bring your exam back on Monday, I'll go ahead and give you an extra point for that problem."


Thanks everyone for your responses! They are much appreciated :)