Determination of a new scale of ortho-steric parameters S0 from N-methylation of pyridines was written by Berg, Ulf;Gallo, Roger;Klatte, Gerd;Metzger, Jacques. And the article was included in Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry (1972-1999) in 1980.Quality Control of 2-Isopropylpyridine This article mentions the following:
The kinetics of quaternization by MeI of 33 substituted pyridines, e.g. 2-ethylpyridine, were measured in MeCN at 30°. The relative rate constants obtained were similar to those observed in other polar aprotic solvents. The magnitude of steric effects observed for all ortho-substituents were estimated from the Broensted plot. A scale of ortho-steric parameters (S0) was proposed. No correlation was observed between S0 and the electronic effect of substituents. S0 Is not solvent dependent. The relative S0 values agree with other exptl. values of the steric size of the substituents. The S0 parameters are discussed in terms of substituent structure relative to the Taft-Kutter-Hansch Es and Charton ν parameters. In the experiment, the researchers used many compounds, for example, 2-Isopropylpyridine (cas: 644-98-4Quality Control of 2-Isopropylpyridine).
2-Isopropylpyridine (cas: 644-98-4) belongs to pyridine derivatives. In contrast to benzene, Pyridine’s electron density is not evenly distributed over the ring, reflecting the negative inductive effect of the nitrogen atom. One of the examples of pyridines is the well-known alkaloid lithoprimidine, which is an A3 adenosine receptor antagonist and N,N-dimethylaminopyridine (DMAP) analog, commonly used in organic synthesis.Quality Control of 2-Isopropylpyridine