Premium
Estimating the stability and reactivity of cyclic tetrahalo substituted germylenes: A density functional theory investigation
Author(s) -
Koohi Maryam
Publication year - 2020
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.4032
Subject(s) - chemistry , isodesmic reaction , hyperconjugation , singlet state , density functional theory , substituent , carbene , reactivity (psychology) , halogen , steric effects , natural bond orbital , computational chemistry , marcus theory , crystallography , reaction rate constant , stereochemistry , photochemistry , kinetics , molecule , catalysis , organic chemistry , atomic physics , excited state , alkyl , medicine , alternative medicine , pathology , physics , quantum mechanics
Abstract The largest unsaturated carbene, cyclonona‐3,5,7‐trienylidene ( 1 H ), emerges as a boat‐shaped transition state (TS) for having a negative force constant (FC). Following the quest for stable germylenes ( 2 X , where X = H, F, Cl, Br, and I) with C 8 H 6 X 4 Ge: formula, the density functional theory (DFT) calculations are carried out to assay the substituent effect on their thermodynamic and kinetic possibilities. These singlet and triplet germylenes ( 2 X ‐ S and 2 X ‐ T , respectively) appear as boat‐shaped minima without imaginary frequencies and the order of their stability estimated by singlet (S)–triplet (T) energy difference (Δ E S‐T = E T − E S ) is 1 H < 2 H < 2 F < 2 Cl < 2 I < 2 Br . The purpose of the present work is to swiftly switch from T carbene to S germylenes through alteration of the substituents and assess the influence of different halogens on the stability and other properties. The 2 Br ‐ S seems as the most stable species. From kinetic point of view, 2 Cl , 2 Br , and 2 I are more stable than some of synthesized germylenes. The stabilization of the S state is essential to stabilize germylenes. This can be achieved by σ‐electron withdrawing and π‐electron donating substituents, of which stabilizing effect can be further increased in the order of steric effect < positive hyperconjugation < negative hyperconjugation < mesomeric effect. Applying suitable isodesmic reactions, we show the π‐donor/σ‐acceptor halogen substituents stabilize not only the S but also the T states, and these groups stabilize 2 X ‐ S more than 2 X ‐ T .