Stable isotopes in organic compounds

All compounds analyzed have higher 5D values than terrestrial samples, confirming the enrichments seen in bulk measurements. Some individual compounds have very high 5D values, in one case as high as 3600 permil (4.6 times the solar system ratio). The high 5D values seem to correlate with structures that include branching methyl groups. 

A major conclusion from analyses of carbon isotopes in organic compounds in chondrites is that 513C values decrease as the number of carbon atoms in the molecule 

Changes in carbon isotopic composition as the number of carbon atoms in a molecule increases. These variations occur in aliphatic and aromatic compounds. 

Compound-specific measurements of hydrogen isotopes have been performed for amino and sulfonic acids in Murchison. Significant enrichments in deuterium suggest interstellar origins for these compounds (more on this below). 

Sulfur isotope compositions in sulfonic acids show a mass-independent enrichment in 33S. Determining fractionations that are not controlled by mass is made possible because sulfur has so many stable isotopes. This feature has been attributed to ultraviolet irradiation of carbon disulfide in space, prior to its reaction to make sulfonic acid. 

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