2010/01/01 by Brianna R. Heazlewood, Alan T. Maccarone, Duncan U. Andrews +8 · 2 citations
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · Chemistry · Earth and Planetary Sciences · Medicine · Pharmacology, Toxicology and Pharmaceutics · #Acrosome #Anatomy #Andrology #Atmospheric chemistry and aerosols #Atomic physics #Axoneme #Biology #Bond cleavage #Botany #Catalysis #Chemical Reactions and Isotopes #Chemistry #Computational chemistry #Deuterium #Fish Biology and Ecology Studies #Flagellum #Genetics #Intramolecular force #Isomerization #Kinetic isotope effect #Mass Spectrometry Techniques and Applications #Medicine #Molecule #Photochemistry #Photodissociation #Reaction mechanism #Reproductive biology and impacts on aquatic species #Scrambling #Sperm #Sperm and Testicular Function #Stereochemistry #Transition state #Ultrastructure
paper · doi:10.1038/nchem.1052
openalex publication_date 2010/01/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Measuring the isotopic abundance of hydrogen versus deuterium atoms is a key method for interrogating reaction pathways in chemistry. H/D 'scrambling' is the intramolecular rearrangement of labile isotopes of hydrogen atoms and when it occurs through unanticipated pathways can complicate the interpretation of such experiments. Here, we investigate H/D scrambling in acetaldehyde at the energetic threshold for breaking the formyl C-H bond and reveal an unexpected unimolecular mechanism. Laser photolysis experiments of CD₃CHO show that up to 17% of the products have undergone H/D exchange to give CD₂H + DCO. Transition-state theory calculations reveal that the dominant mechanism involves four sequential H- or D-shifts to form CD₂HCDO, which then undergoes conventional C-C bond cleavage. At the lowest energy the molecule undergoes an average of 20 H- or D-shifts before products are formed, evincing significant scrambling of H and D atoms. Analogous photochemically induced isomerizations and isotope scrambling are probably important in both atmospheric chemistry and combustion reactions.