Synthesis and Acidity of 5-Phenyltetrazol-2-ylalkanoic Acids and the Corresponding 5-(5-Phenyltetrazol-2-ylalkyl)tetrazoles

We have obtained 5-phenyltetrazol-2-ylalkanoic acids and their derivatives containing terminal nitrile, amide, and tetrazol-5-yl groups. Tetrazolylalkanoic acids with two (pK_a 4.93) and three (pK_a 5.45) bridging methylene groups are weaker acids than the corresponding ditetrazoles pK_a 4.68 and 5.29 respectively). However, the acidity of 5-phenyltetrazol-2-ylacetic acid (pK_a 3.12), is higher than acidity of the corresponding ditetrazole (pK_a 3.27).