Below is the table 1 with the data of 5-X-2-furoic acids. In the figures 1-3, it is clear from the correlation coefficients, the pKa data of 5-X-2-furoic acids correlated well (Hammett ρp = -1.377, R = 0.9982) with Hammett σp values with a deviation of the lone -COOH substituent. This could be due to the week hydrogen bonding interaction as shown below in scheme 5 in one of the 2-furoic acid (trans) conformers between H of -COOH and O of the ring . Therefore, good correlation of pKa data with para-substituent constants, the 5 position of the 2-furoic acid is best assumed as paraposition. The Hammett ρm is reported for 4-X-2-furoic acids as 1.40 with a correlation coefficient of 0.988 . But to reproduce the plot here in this work, the journal Iowa State Coll. J. Sci. is not approachable.