Intramolecular forces: the molecular structure and conformation of 2-cyclopropylpyridine and 4-cyclopropylpyridine

The expected shortening of the distal cyclopropyl C-C bond length is observed in 2-cyclopropylpyridine, while the calculated difference between vicinal and distal C-C bonds had to be assumed in the experimental study of 4-cyclopropylpyridine.