Assigning structures to diastereomeric aliphatic α,α'-dibromo ketones

X-ray crystal structures are reported for two symmetrical aliphatic α,α'-dibromo ketones: a meso diastereomer of 3,5-dibromo–2,2,6,6-tetramethylheptan-4-one, and a rac isomer of 4,6-dibromo–2,2,3,3,7,7,8,8-octamethylnonan-5-one. Using these secure assignments and a previously confirmed structure for the diastereomers of 2,4-dibromopentan-3-one, we show in this study that gas-liquid chromatography (GLC) retention times (meso > rac) can be used to confidently assign the diastereomers for a range of symmetrical and unsymmetrical aliphatic α,α'-dibromo ketones. 1H NMR chemical shifts for the >CHBr hydrogen(s) can also be corroboratively used for assignment purposes (δracH > δmesoH).Key words: α,α'-dibromo ketones, X-ray crystal structures, GLC retention times, isomer assignment