With the increasing importance of multiply tritiated molecules in biomedical research, it becomes important to know what impurities may arise as a consequence of the b-decay of one of the unstable nuclei. 3H b-decay is a well-documented method for producing gaseous cations under high pressure conditions. Such experiments typically make use of multiply tritiated starting materials, which are allowed to stand in a sealed bulb for several months. Because there is more than one tritium in a given molecule (and because the odds are very low that more than one of them will decay within the time span of the experiment) the products that are recovered will most likely contain radiolabel. Thus standard radio tracer techniques can be used to analyze the neutral products that result from ion-molecule reactions of the tritiated cations. Tritium b-decay can be used to produce cations at atmospheric pressure. We are using 1,2-ditritioethanol (TCH2CHTOH) as a source of radiolabeled, gaseous protonated acetaldehyde and propose to synthesize 2,3-ditritio-n-propanol as a source of radiolabeled, gaseous propionaldehyde. TCH2CHTOH and TCH2CHTCH2OH are to be freshly prepared by transesterification of the corresponding tritiated alkyl docosanoates in an evacuated sealed tube. Volatile radioactive compounds are never open to the atmosphere (except when frozen or in dilute solution). The TITLE: Ester Precursors for Ditritiated Alcohols (Continued) nonvolatile starting materials are to be prepared by catalytic addition of T2 to vinyl docosanoate at the National Tritium Labelling Facility (NTLF) at Berkeley and purified by HPLC at the NTLF. In the past, this ester has required repurification about every 6 months. A radioactive material laboratory is currently being installed at UCR for this purpose, which will permit us to perform syntheses using techniques that are not restricted to sealed tubes (such as preparation of tritiated haloethanes). Electrophilic Attack of Double Bonds by Protonated Aldehydes Many carbon-carbon bond-forming reactions make use of electrophilic attack of sp2 carbon by carbocations. Many of these are so well known that they correspond to organic name reactions. Among synthetic chemists there is a great deal of contemporary interest in cases where stereo- and regioselectivity can be controlled. Examples include the acid-catalyzed """"""""eno""""""""-reaction, the Prins reaction, the Sakurai reactions, and the aldol condensation. The synthesis of these precursors allows the formation of radiolabelled protonated acetaldehyde and propionaldehyde to probe the mechanisms of these reactions in the gas phase.
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