Question

Select the appropriate reagent for each step of the following synthesis in which propionyl chloride is made with a carbon-13 isotope in position 2, starting with 13CO2. (The 13C atoms are shown in a green color). Identify which carbon atom in each intermediate would be labeled by clicking on the atom until it turns green. (If you make a mistake, click on the atom again to turn it back to black. Be careful not to select a bond or an oxygen.)

Answer 1

Synthes is of propionyl chloride Carbon dioxide reacts with methyl magnesium bromide and followed by hydrolysis to form acetic acid. It can be reduced with lithium aluminum hydride to form ethyl alcohol CH3 1. CH3MgBr 1. LiAlH4 2. H2O Carbon dioxide 2. H30 Acetic acid Ethyl alcohol Ethyl alcohol reacts with phosphrous tribromide in pyridine to form ethyl bromide. It is reacted with Mg metal in the presence of dry ether to form ethyl magnesium bromide (Grignard reagent) CH3 CH3 CH3 H:"C-011 Ethyl alcohol PBr3, pyridine Mg ether Ethyl bromide Ethylmagnesium bromide (Grignard reagent) Ethyl magnesium bromide reacts with carbon dioxide and followed by hydrolysis to form propanoic acid. It is reacted with thionyl chloride to form propionyl chloride CH3 H,C H C SOC, Cl 2. НО Propionyl chloride Ethylmagnesiu bromide Propanoic acid (Grignard reagent) In all intermediates include final product, the C-13 isotope is labelled with green color