Sodium rubidium tartarate

In 1951, it became possible to determine whether Rosanoff s guess was right. Ordinary X-ray crystallography cannot distinguish between a d and a l isomer, but by use of a special technique, Bijvoet was able to examine sodium rubidium tartrate and found that Rosanoff had made the correct choice. It was perhaps historically fitting that the first true absolute configuration should have been determined on a salt of tartaric acid, since Pasteur made his great discoveries on another salt of this acid. 

We can now end this historical journey. We have walked through the early days of stereochemistry in the company of giants. In 1949, almost exactly 100 years after the first resolution of d,Martaric add by Pasteur, the Dutchman Bijvoet (16), using x-ray diffraction, determined the actual arrangement in space of the atoms of the sodium rubidium salt of (+)-tartaric add, and thus made the first determination of the absolute configuration about an asymmetric carbon. To further complete the link with the past, Bijvoet did this work while the Director-of the van t Hoff Laboratory at the University of Utrecht. 

Tartaric acid, HOOCCHOHCHOHCOOH, has played a key role in the development of stereochemistry, and particularly the stereochemistry of the carbohydrates. In 1848 Louis Pasteur, using a hand lens and a pair of tweezers, laboriously separated a quantity of the sodium ammonium salt of racemic tartaric acid into two piles of mirror-image crystals and, in thus carrying out the first resolution of a racemic modification, was led to the discovery of enantiomerism. Almost exactly 100 years later, in 1949, Bijvoet, using x-ray diffraction—and also laboriously—determined the actual arrangement m space of the atoms oY the sodium rubidium salt of (-f )-tartaric acid, and thus made the first determination of the absolute configuration of an optically active substance. 

In 1951, the Dutch chemists J. M. Bijvoet, A. F. Peerdeman, and A. J. vanBommel, using X-ray crystallography and a new technique known as anomalous dispersion, determined that the sodium rubidium salt of (+)-tartaric acid had the RJi configuration. Because (-l-)-tartaric acid could be synthesized from (—)-glyceraldehyde, (-)-glyceraldehyde had to be the S enantiomer. The assumption, therefore, that (-l-)-glyceraldehyde had the R configuration was correct ... 

The salt of tartaric acid analyzed by X-ray crystallography was the sodium rubidium salt of (+)-tartaric acid. X-ray crystallography of biomolecules is described in the boxed essays in Sections 14.13 and 26.8. 

In 1951, the Dutch scientist J. M. Bijvoet developed a special x-ray technique that solved the problem. Using this technique on crystals of the sodium rubidium salt of (+)-tartaric acid, Bijvoet showed that it had the (R,R) configuration. So this was the tartaric acid studied by Pasteur, and racemic acid was a 50 50 mixture of the R,R) and (S,S) isomers. The meso form was not studied until later. 

If the crystal-structiu-e analysis is made on a derivative containing a heavy atom, with x-rays of wavelength appropriate to the particular heavy atom (that is, Br or I with CuKa radiation), it is possible to determine the absolute configuration of an enantiomorphous molecule. This method was first demonstrated with the rubidium sodium salt of dexiro-tartaric (l-threaric) acid tetrahydrate by Bijvoet and coworkers in 1951. The results confirmed the configuration of dextro-i vi nc acid originally assigned by... 

A series of half-neutralized salts of tartaric acid are also found to crystallize in the orthorhombic P2j2j2j, space group (all containing four molecules in the unit cell) and are thus potentially resolvable by a mechanical separation. Ammonium hydrogen tartrate is found to crystallize with a = 7.648 k,b= 11.066 A, and c = 7.843 A [29]. Sodium hydrogen tartrate crystallizes with a = 8.663 k,b= 10.583 A, and c = 7.228 A, while potassium hydrogen tartrate crystallizes with a = 7.782 A, b = 10.643 A, and c = 7.608 A [29]. Finally, rubidium hydrogen tartrate is found to crystallize with a = 7.923 k,b= 10.988 A, and c = 7.653 A [29]. 

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