[Twickel]

Attached are images of the procedures [ chemical structures only], if more information is needed I will
post them.

From part 2 I have the following products. 2a  preparation of bis-oxalamide from racemic amine
2b Preperation of (S,S)-bisoxalamide

Q 1) Discuss the results of your TLC, what products do the dots correspond to? I marked the left most one as 2a second one as 2b and the third dot as a mixture of 2a +2b. I do not know how to analyse this.
Q 2) If the resolution of 1-phenylethylamine provided a 1.0 g sample of the amine enriched in the (S)-enatiomer with an enatiomeric excess of 80%, what mass of each enatiomer would be present?
Q 3) What ratio of stereoisomers of the bis-oxalamide would be produced on reacting the sample discussed in question 2 with diethyl oxalate?

Note: the first column of the TLC i.e 2a actually has 4 circles the first one is so faint, it did not come ip on the scan


I have not done EE before and we have no examples in our manual.

Help is much appreciated.

[discodermolide]

There was a recent discussion on calculating %ee in this forum. Link:
http://www.chemicalforums.com/index.php?topic=62854.0

As to the TLC, it looks to me that the middle spots are a mixture of the left and right spots. Don't forget that you have a mixture of diastereoisomers present which are separable.
Two things, please be a bit more specific as to what the compounds are you put on the plate, i.e. with names, I can't see anything in the reaction labelled 2a or 2b.
What was the detection method for the spots, UV light or something else, (Spray) or both?

[Babcock_Hall]

enantiomeric excess:  http://www.icmab.es/resolve/enantiomeric-excess.html

[Twickel]

Is the answer 0.6g of the s enantiomer and 0.4g of the R?

With regards to the2a and b section
2a- we prepared a bis-oxalamide from racemic amine, that is all it says [I can post the method if needed]

part2b we prepared [S,S]-bisoxalamide from the (S) enriched amine.

The TLC was observed under UV light, and was eluted with dichloromethane

[discodermolide]

OK then your label 2b is a 1:1 mixture of diastereoisomers prepared from the racemic mixture it is actually the third spot and should be 2a.
The left spot, your 2a is actually the preparation with the enriched amine and should actually be 2b.

The middle spot is a mixture of both of them.

Please give such information in the post it would make it easier to understand.

[Babcock_Hall]

0.6 grams and 0.4 grams does not sound correct.  Plug these into the formula for ee, and see what number you calculate.

[OC pro]

Nice experiment. Miss the hundreds of crystallizations for separation of enantiomers. Oxalic acid in fact worked always pretty well for me.
The aforementioned crystallization should work really good.
Again a student fails at simple calculation (*shaking head*). Is it really that difficult?

[Twickel]

0.98g of the S amine and 0.1g of the R amine

major = +80/2+50 minor = -80/2+5

[Twickel]

Sorry about that I meant 0.9g of the S enantiomer and 0.1g of the R enantiomer.

With regards to the TLC pate, I do not understand what you mean.
I have re drawn the circles better

The first set of dots (left most) was meant to be the compound formed in 2a- preparation of bisoxalamide from racemic amine
The second set of circles corresponds to a mixture of part 2a and 2b- a combination of preparation of bisoxalamide from racemic amine and preparation of(S,S)-bisoxalamide
The third set of circles (the one with two circles only) is meant to be  preparation of(S,S)-bisoxalamide

Why do I see these results for each of the dots?

[discodermolide]

Right the reaction of the amine (racemic) with the bis-oxalimide gives a mixture of diastereoisomers and a meso compound three spots.
The third set, reaction of the chiral amine and the oxalimide gives two diastereoisomers, two spots of roughly equal intensity.
The middle spots are simply a mixture of the left and right reaction mixtures.

[Twickel]

I thought the third set, the one with two circles, was only one enantiomer. If I react an S enriched amine with the oxalamide, I get two diasteroisomer?

[discodermolide]

you cannot separate enantiomers by TLC.
Your enriched amine will give two diastereoisomers.