[curiouscat]

Consider the two-step synthesis A  B  C as shown below. So far as I can tell, A doesn't have a chiral center but both B and C do?

Is it possible to say if B / C would be R or S configurations or a racemic mixture? Or does this have to be experimentally determined?   For the first step H2O2 + HCl  mixture is used & for the second step the reagent is NaOH.


A B

B C

[discodermolide]

You can buy both enantiomers of epichlorohydrin.

Under your reaction conditions I would expect a racemic mixture.

What you would need to do is a resolution by making a chiral ester and separating the diastereoisomers. And thats just to get authentic samples.

[curiouscat]

Under your reaction conditions I would expect a racemic mixture.

What you would need to do is a resolution by making a chiral ester and separating the diastereoisomers. And thats just to get authentic samples.

Thanks @disco! For starters would measuring the optical activity in a polarimiter help at all? Or not? I guess it'd tell me if it was perfectly racemic with no enantiomeric excess?

If I get some, non-zero rotation though, I wouldn't know how enantiomerically pure that was without the specific rotation known?

[Enthalpy]

Maybe perhaps just a suggestion:

you could try to crystallize your product. Most probably, the R and S forms arrange precisely as 1:1  in the crystal. Then you can sort out which crystals show zero activity, which (if any) do rotate, and how much stays in the solvent. Weigh everything and get the ratio you want.

My opinion is little worth here, so better get more opinions.

[discodermolide]

Under your reaction conditions I would expect a racemic mixture.

What you would need to do is a resolution by making a chiral ester and separating the diastereoisomers. And thats just to get authentic samples.

Thanks @disco! For starters would measuring the optical activity in a polarimiter help at all? Or not? I guess it'd tell me if it was perfectly racemic with no enantiomeric excess?

If I get some, non-zero rotation though, I wouldn't know how enantiomerically pure that was without the specific rotation known?

Right, you need a chiral reference. The best will be is chiral HPLC.

[curiouscat]

Thanks! Also, whatever be the enantiomeric purity of B, would C would be similar? i.e. say B is almost pure R form would C be also?

[discodermolide]

Yes, it goes by the sequence rules.