Synthetic methods employed in this series of compounds

Synthetic methods employed in this series of compounds As direct chlorination or bromination of a carboxylic acid usually gives the a-substituted acid, such methods are useless for the preparation of the w-substituted acids ad hoc methods therefore had to be found for the preparation of each individual W fluorocarboxyhc acid and its derivatives. 

The starting point for the 5-fluoropentanecarboxylic esters was cyclohexanone, which was oxidized to 5-hydroxypentane-carboxylic acid by a modification of Robinson and Smith s method. This was then converted into the bromo acid by means of hydrogen bromide and sulphuric acid.  

5-Bromopentanecarboxylic acid was converted into the appropriate esters as follows Br-[CHj] -co h 

The 7 fluoroheptanecarboxylates were synthesized from hexamethylene dibromide according to the following scheme  

The splitting of (XII) took place smoothly with constant-boiling hydriodic acid to give the pure iodo acid. The fluorina-tion of (XIII) was more facile than that of (XIV). In fact, with the latter acid, hydrogen iodide was eliminated to some extent with the production of ethyl hept-6-enecarboxylate, which was effectively removed by conversion into the dibromide with bromine, followed by distillation. 

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