Deprotonation of 1,2-Dialkylpyridinium Ions:  A DFT Study of Reactivity and Site Selectivity

Abstract

A site-selectivity model, based on the Fukui function as a local reactivity descriptor, has been applied to 1,2-disubstituted pyridinium ions incorporating two competing sites of similar reactivity, i.e., 1-methylene and 2-methylene, which may undergo deprotonation depending on the nature of substituent present on these moieties. Applicability of the local HSAB rule, in context with the Li-Evans' generalized HSAB principle suggesting the hard-hard interactions to be controlled by minimum Fukui function, has been illustrated. Global and local reactivity descriptors have been computed by carrying out DFT calculations at B3LYP/6-31++G** level using Mulliken and NPA methods for charge analysis. A comparison with the calculated deprotonation energies involving two sites indicates that the observed site selectivity in differently substituted pyridinium ions is better explained by the Li-Evans rule of minimum Fukui function for hard-hard interactions.

Surfactant-Derived Amphiphilic Carbon Dots with Tunable Photoluminescence

“…The DFT calculations performed for dialkylpyridinium salts by Gupta et al show that the deprotonation in the presence of base takes place preferentially on the α-carbon of the alkyl chain, which is also assumed here; see Figure . The process generally described as hydrothermal carbonization may include several chemical reactions, such as hydrolysis, dehydration, decarboxylation, polymerization, aromatization, etc .…”

Stability, Reactivity, and Aromaticity of Compounds of a Multivalent Superatom

“…Philicity values provide the corresponding information regarding the attack by a soft species. Although numerical calculations 37 might show that in some cases the minimum Fukui function (FF) 38 sites are the best for the hard-hard interactions and the charges may fail to identify those sites due to the intrinsic inadequecies associated with density partitioning, 39 the least reactive sites 32 having the minimum FF values may counter the Klopman dictum 36 of the charge-controlled hard reactions as well as the original definition of FF. 32 The minimum FF condition may, however, be used for a level playing field 40 for a dominantly charge-controlled reaction with two potential sites that are equally favorable electrostatically.…”

Positive Carbon Dots Induced Electrodeposition of NiCo-LDH Nanosheets for High-Performance Supercapacitors

“…In the presence of NaOH, deprotonation of CPC first takes place on the α-carbon of the alkyl chain. 32 Prompted by strong ultrasonication, hydrophobic groups of surfactants spontaneously converge, followed by polymerization and carbonization, forming carbonized cores of carbon dots. Owing to the hydrophilic effect of the pyridine groups, most of such groups will remain on the surface of carbon dots so as to form positively charged p-CDs.…”

“…The preparation process of p-CDs and LDH/CD x @CC is illustrated in Scheme . In the presence of NaOH, deprotonation of CPC first takes place on the α-carbon of the alkyl chain . Prompted by strong ultrasonication, hydrophobic groups of surfactants spontaneously converge, followed by polymerization and carbonization, forming carbonized cores of carbon dots.…”